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2026

Biogeochemical controls on dissolved micronutrient (Ni, Cu, Zn, Cd) distributions in the Equatorial Pacific Ocean

Date: 2026-01-06
Speaker: Dr. Naman Deep Singh
Venue: Ground Floor Lecture Hall

Abstract

The Equatorial Pacific Ocean (EPO) is among the most productive oceanic regions and is characterized by strong CO2 outgassing, playing a pivotal role in the global carbon cycle. Here, we present the distributions of micronutrients along the German GEOTRACES GP11 transect in the EPO during a developing El Niño. This study aims to assess the biogeochemical controls governing micronutrient distributions along the transect, which are critical for elucidating potential linkages between surface productivity and nutrient supply. Model estimates combined with observational constraints indicate that equatorial upwelling and strong zonal currents exert primary controls on micronutrient fluxes and biological uptake ratios. These findings have important implications for the bioavailability of micronutrients in the surface EPO under an increasing frequency of extreme El Niño and La Niña events, which modulate upwelling strength and Equatorial Undercurrent (EUC) intensity across the EPO. Overall, this study highlights the differential impacts of water mass mixing and vertical processes including, organic matter remineralization, particle scavenging, and benthic fluxes, on micronutrient distributions in the EPO and provides new insights into their inter-basin variability and biogeochemical cycling in the Pacific Ocean. About the speaker: Dr. Naman Deep Singh is a geochemist and completed his integrated BS-MS degree at the Indian Institute of Science Education and Research (IISER) between 2010 and 2015, followed by a Ph.D. at the Physical Research Laboratory from 2015 to 2020. He is currently working as a postdoctoral researcher at GEOMAR Helmholtz Centre for Ocean Research in Kiel, Germany. His research interests focus on understanding the biogeochemical cycling of trace metals in the ocean and their influence on biological ocean productivity and chemical weathering processes in terrestrial systems.

2025

Understanding Dwarf Novae Type Cataclysmic Variables

Date: 2025-12-31
Speaker: Ayush Rana
Venue: 113/114, Thaltej Campus

Abstract

Cataclysmic Variables (CVs) are close interacting binary systems consisting of a white dwarf accreting material from a late-type main-sequence companion via Roche-lobe overflow. Due to their small orbital separations, typically a few solar radii, CVs exhibit short orbital periods of a few hours and display strong photometric variability. Dwarf novae are a prominent subclass of CVs and are characterised by recurrent optical outbursts with amplitudes of 2–6 magnitudes and recurrence timescales ranging from weeks to months. These outbursts are understood with the disk instability model (DIM), in which thermal–viscous instabilities in the accretion disk drive transitions between quiescent and outburst states. Dwarf novae provide an excellent laboratory for studying accretion disk physics and time-dependent disk evolution. In eclipsing systems, changes in the disk structure can be probed using eclipse depth and out-of-eclipse flux measurements. Recent high-cadence photometric studies have revealed hysteresis behaviour in eclipse fraction diagrams, indicating a temporal lag between variations in mass accretion rate and disk radius during outburst cycles. In this talk, I present an overview of cataclysmic variables with emphasis on dwarf novae, their outburst mechanisms, and observational diagnostics of accretion disk evolution. I also outline the motivation and objectives of ongoing work focused on studying the evolution of accretion disks in eclipsing dwarf novae.

Investigating the Chautang-Drishadvati-Harappan connection

Date: 2025-12-30
Speaker: Aditya Vikram Mishra
Venue: Ground Floor Lecture Hall

Abstract

Numerous Harappan urban centers have been discovered along the floodplains of Ghaggar and Chautang in northwestern India. These minor seasonal streams could not have supported large settlements in the past. Many believe that these streams occupy the channels of two mighty, perennial rivers of yesteryears - the Sarasvati and the Drishadvati, respectively. Although the timelines of the river Sarasvati's evolution/demise and the nature of its water/sediment sources have been established, very little is known about the river Drishadvati and its connection to the Harappan civilization. My PhD study aims to investigate this question using modern geochronological, geochemical, and isotopic tools. In the seminar, I shall provide a brief overview of my thesis problem.

Geochemical Investigation of Neoproterozoic Bhander Shales: Implications towards Provenance

Date: 2025-12-30
Speaker: Deependra Singh
Venue: Ground Floor Lecture Hall

Abstract

The Neoproterozoic Eon, which spanned 1000-538 Ma, marks an important time in crustal history between the break-up of Rodinia and the assembly of Gondwana. To understand the evolutionary history of the Earth’s crust in this time frame, Sedimentary basins act as an excellent natural laboratory by preserving the signature of evolution in the sedimentary rocks. The Vindhyan basin of India is such an archive which provides an opportunity to investigate sediment provenance and basin evolution by the analysis of its sedimentary rocks. So, to understand the provenance of the sediments of this vast basin becomes important to characterize the source of these sediments and to infer the tectonic setting and climatic conditions of the source region at that time. In this talk, I will discuss the basic idea of the sedimentary provenance of Neoproterozoic shales of the Bhander group from the Rajasthan section of the Vindhyan Basin. I will also present some preliminary results of my work and my future plans in this direction.

Understanding the Spectral Energy Distribution (SED) of Blazars

Date: 2025-12-29
Speaker: Ashad Ahmad
Venue: 113/114, Thaltej Campus

Abstract

Relativistic jets in blazars are sites of extreme plasma conditions, efficient non-thermal particle acceleration, and broadband radiation extending from radio to very-high-energy γ-rays. Their spectral energy distributions (SEDs) exhibit a characteristic double-humped structure, commonly interpreted as synchrotron emission at low energies and inverse-Compton or hadronic processes at high energies. The observed luminosities, rapid variability, superluminal motion, and one-sidedness of the jet impose strong constraints on the size, speed, and geometry of the emitting region, requiring relativistic beaming and compact dissipation zones within the jet. Leptonic and hadronic emission models are commonly employed to reproduce blazar SEDs and multi-wavelength variability, but these models typically rely on simplified assumptions for the underlying non-thermal particle energy distributions. Such non-thermal spectra cannot arise from purely thermal processes, indicating the presence of efficient particle acceleration operating in relativistic jet environments.

Role of ocean anoxia in the Permian–Triassic crisis: Evidence from geochemical and isotopic data

Date: 2025-12-26
Speaker: Nilima Mishra
Venue: Ground Floor Lecture Hall

Abstract

The Permian–Triassic boundary (“Great Dying”), the most severe mass extinction in Earth's history, was accompanied by extreme perturbations in ocean oxygenation. Reconstructing ocean redox conditions during this event is critical for evaluating the vulnerability of modern oceans and for distinguishing reversible environmental stress from tipping-point behavior in Earth’s life-support system. In this talk, I will discuss how molybdenum isotopic geochemistry provide a powerful framework for reconstructing changes in global ocean redox conditions across the Permian–Triassic boundary.

Assessing environmental microplastics using FTIR

Date: 2025-12-26
Speaker: Maitri Maheshwari
Venue: Ground Floor Lecture Hall

Abstract

Microplastics are the fragmented particles of plastic debris that are generated from degradation or waste release, contaminating our environment. Found in mountains, polar caps, and deep-ocean trenches, MPs are proving their ubiquitous nature with every new study. To accurately assess their presence and effects on our ecosystems, various analytical techniques have been developed, of which Fourier Transform–Infrared Spectroscopy (FTIR) is widely employed. In the talk, I will discuss this non-destructive and convenient method and how it has made MP analysis easier. Furthermore, certain limitations need to be addressed, and complementary solutions are necessary to achieve reliable results.

Stellar Streams in the Milky Way's Halo

Date: 2025-12-26
Speaker: Arvind
Venue: 113/114, Thaltej Campus

Abstract

The Milky Way galaxy is our home galaxy, hosting our solar system and billions of other stars. One of the key questions in galactic astronomy is to understand the formation and evolution of galaxies. As we are part of the Milky Way, it provides us with a unique opportunity to study its components in great detail, allowing us to gain a deeper understanding of how galaxies form and evolve in general. According to the cosmological paradigm, galaxies form through hierarchical accretion of lower-mass galaxies. The recently discovered stellar streams in the Milky Way's halo are direct evidence of these merger events. Stellar streams form due to the tidal disruption of a globular cluster or dwarf galaxy that orbits the Milky Way. In this talk, I will discuss about the stellar streams, how they are detected, and what information we obtain from their spectroscopic follow-up. I will also discuss about the target selection for the spectroscopic observation of the stream stars. Determining the age of the stellar streams is crucial because they serve as a record of the Milky Way's growth, revealing its merger history and assembly timeline.

Spectro-Polarimetry of Symbiotic Star

Date: 2025-12-24
Speaker: Sube Singh Gurjar
Venue: 113/114, Thaltej Campus

Abstract

Symbiotic stars are interacting binary systems composed of a cool red giant and a hot white dwarf. Material is transferred from the giant to the dwarf through a stellar wind or in some systems,via Roche-lobe overflow. An intriguing fact of symbiotic systems is their extremely low known population; only around 300 such system are known against their predicted population of around 300,000 in our Galaxy. Moreover,these exhibit unique emission features at 6825 Å and 7082 Å, which are caused by the Raman-scattering of O VI doublet at 1032 and 1038 Å. As these features are a result of scattering, they show polarization signatures and hence can be used to probe the morphology and kinematics of the systems. We plan to undertake a long term spectro-polarimetic observational study of such systems, wherein any temporal variability of these Raman scattered features would be explored using spectro-polarimetric observations from ProtoPol instrument on PRL 2.5m telescope. In addition, we are upgrading the existing MFOSC-P instrument on PRL 1.2m telescope with newer spectro-polarimetric capabilities.

Novel Tools to assess the Health Risks from Outdoor and Indoor Air Pollution

Date: 2025-12-23
Speaker: Dr. Vishal Verma
Venue: Ground Floor Lecture Hall

Abstract

The capability of ambient particulate matter (PM) to generate reactive oxygen species (ROS), conveniently called the oxidative potential is proposed as a better metric for relating the PM pollution with health effects. In this talk, I would present our work on the measurement of oxidative potential of ambient and indoor PM. Through these measurements and comparisons, we demonstrate the need for a comprehensive toxicity and health impact assessment of PM emanating from indoor and outdoor sources.

Revealing the State of the Early Intergalactic Medium through 21-cm Signal Analysis

Date: 2025-12-22
Speaker: Dr. Raghunath Ghar
Venue: 113/114, Thaltej Campus

Abstract

Measurements of the power spectrum of the redshifted 21-cm signal from the Epoch of Reionization (EoR) provide crucial insights into the ionization and thermal states of the intergalactic medium (IGM) and depend sensitively on the nature of the early radiation sources. Recent upper-limit constraints from SKA precursor experiments such as MWA, HERA, and LOFAR have already begun to exclude several extreme reionization models (e.g., Ghara et al. 2020, 2021). In these models, the 21-cm signal fluctuations are primarily driven by rare, large ionized or emission regions in the early Universe. With forthcoming, more stringent upper limits, particularly from small-scale power spectrum measurements by the SKA, the constraints on the IGM state during the EoR are expected to improve significantly. In this presentation, I will discuss which reionization scenarios and IGM conditions are likely to be ruled out first with SKA observations. I will also summarize the current understanding of the IGM properties during the EoR based on results from ongoing 21-cm signal experiments.

Size-resolved Sources, Composition and Optical Characteristics of Brown Carbon Aerosols

Date: 2025-12-16
Speaker: Garima Verma
Venue: Ground Floor Lecture Hall

Abstract

Atmospheric aerosols are critical component of the Earth's climate system and a dominant factor in urban air quality. However, their precise impact on climate and human health is one of the largest uncertainties in modern atmospheric science (IPCC, 2021). Organics are the least studied components in ambient aerosols because of their multiple natural and anthropogenic origins, multifarious chemical composition, and complex formation mechanisms (Andreae and Gelencsér,2006). Brown carbon (BrC), the light absorbing fraction of organic carbon (OC), exerts vital effects on climate change as well as human health. BrC optical properties and radiative forcing effects as a function of aerosol size, which would provide direct evidence as to how important is BrC in driving aerosol climate forcing over Indian megacities. Size-segregated studies offer critical insights into distinct sources and formation pathways that are often obscured in bulk measurements. Understanding of sized aerosols is therefore necessary to comprehend their chemical reactivity, atmospheric lifetime, and impacts on human health and climate.

N₂ Fixation in Inland Water Ecosystem

Date: 2025-12-16
Speaker: Md. Fahad Alam
Venue: Ground Floor Lecture Hall

Abstract

We know that the atmosphere is composed of approximately 78% nitrogen, but it is inaccessible to most organisms due to the inert nature of N₂ gas. In that case, N₂ fixation plays a role in transforming this N₂ gas into a bioavailable form. There are a lot of Studies are happening on N₂ fixation in the world and in PRL, also, but Most are in marine ecosystems. Here, I will discuss the inland water ecosystem, as inland and coastal waters cover less than 10% of Earth's surface area, yet they can contribute 15-20% to the global nitrogen budget, which was previously underestimated. I will talk about the water column and benthic N₂ fixation in the inland water ecosystem.

Marine Microbes at the Air–Sea Interface: From SML Ice-Nucleating Bacteria to Microbial Aerosols in the Indian Ocean

Date: 2025-12-08
Speaker: Prof. Koji Hamasaki
Venue: Room no. 469, THEPH Division Seminar Room

Abstract

Sea-spray aerosols (SSA) are a major natural source of cloud condensation nuclei (CCN) and ice-nucleating particles (INPs), yet the microbial drivers behind their production and variability remain poorly constrained. The sea-surface microlayer (SML), enriched in organic matter and microorganisms, acts as a selective interface that promotes the transfer of microbe-associated particles to the atmosphere. In this talk, I present two complementary studies that reveal a consistent role of specific marine bacterial lineages—particularly Flavobacteriia and Gammaproteobacteria—in shaping the composition and cloud activity of SSA. First, cultivation-based experiments in a coastal inlet of Japan identified SML bacteria from these groups exhibiting heat-labile, protein-associated ice-nucleating activity above –15 °C, demonstrating their potential as INP sources. Second, ocean-basin-scale microbial profiling during the research cruise across the Bay of Bengal and southeastern Indian Ocean showed that these same taxa are selectively aerosolized from particle-associated fractions, whereas coarse aerosol particles over the Bay of Bengal were more influenced by terrestrial intrusions. This highlights strong ecological and atmospheric controls on which marine microbes enter the air. Together, our findings indicate that microbe-rich SML communities—especially Flavobacteriia and Gammaproteobacteria—represent dynamic contributors to cloud-active aerosols, underscoring the need to integrate microbial ecology into predictions of ocean–atmosphere climate feedbacks. About the speaker: Professor Koji Hamasaki's research is focussed on understanding the microbial diversity and functions within surface ocean ecosystems and their critical roles in biogeochemical cycles. His group is notably recognized for pioneering studies on "actively growing bacteria" in natural seawater, employing advanced bromodeoxyuridine (BrdU) incorporation methods to investigate various metabolic processes, including bacterial photosynthesis, nitrogen fixation, and organic sulfur degradation. More recently, his research has concentrated on the specific role of microbial activity at the air-sea interface and its direct influences on climate processes.

Multiple Emission-Line Diagnostics of the Accretion Process in Young Stars

Date: 2025-12-04
Speaker: Kushagra Srivastav
Venue: 113/114, Thaltej Campus

Abstract

Young stars consist of a prestellar core, a circumstellar disk, and an envelope. Material from the envelope accretes to the disk, and through angular-momentum loss or removal, disk material is transported onto the central star. Circumstellar disks are therefore central to both stellar growth and planet formation, making them crucial for understanding the early stages of stellar evolution. In low-mass pre-main-sequence stars, accretion proceeds through magnetospheric funnels that channel disk material onto the stellar surface, generating accretion shocks that result in an excess emission in the UV region and strong emission lines. Classical T Tauri stars (CTTSs) show highly variable accretion across multiple timescales. The origins of this variability remain unknown. In this seminar, I will present a detailed analysis of a classical T Tauri star using multiple emission-line diagnostics to investigate its accretion properties and discuss various line diagnostics related to star-disk interaction processes.

The Evolution of Granite-Greenstone Belts of the Western part of Dharwar Craton, Dharwar Craton, South India

Date: 2025-12-02
Speaker: S V Balaji Manasa Rao
Venue: Online

Abstract

The evolution of granite-greenstone belts within the Western Dharwar Craton (WDC), a Paleoarchean-Neoarchean crustal accretion, represents the major Archean records of Early Earth. In this contribution, an integrating field relationships-whole-rock geochemistry (major/trace elements, REE patterns), and isotope systematics (Sm-Nd, Lu-Hf) depict an initial TTG-komatiite formation at 3400-3300 Ma linked to juvenile mantle inputs and elevated geothermal gradients, and a mixed tectonic setup. Subsequently, the dome-and-keel architectures emerge through subduction and plume tectonics represented by Sargur Group volcanics (~3.3 Ga), indicating high mantle potential temperatures and distinct tectonic manifestation of Archean Earth. While the younger Bababudan (~2.9 Ga) and Chitradurga (~2.7 Ga) greenstones hosting volcano-sedimentary assemblages reflect back-arc volcanism atop stabilised TTG basement, with two phases of 3.0Ga and 2.6 Ga. The Isotopic U-Pb zircon and radiogenic isotope data reveal episodic crustal growth, contrasting WDC's stable, thick (~42-51 km) core with major growth events at 3.35-3.25Ga, including TTG and Komatiitic Volcanism. Vertical tectonics dominate over nascent subduction, underscoring plume-driven nucleation of proto-cratons globally. Therefore, the eventual formation of granite greenstone belts of Western Dharwar Craton from a wide early Earth time window and proxies to investigate the sequential evolution of Archean cratonic units.

Propagation of Solar Energetic Particles in the Heliosphere

Date: 2025-11-27
Speaker: Ritik Dalakoti
Venue: 113/114, Thaltej Campus

Abstract

Solar Energetic Particles (SEPs) are charged particles with energies ranging from keV to several GeV, accelerated during solar flares and CMEs. Understanding SEPs is crucial for space weather. These particles generally follow the large-scale interplanetary magnetic field, however, heliospheric magnetic turbulence repeatedly scatters them. This scattering governs SEP propagation, and diffusion parameters such as the parallel diffusion coefficient quantify the strength of diffusion along magnetic field lines. By combining X-ray spectral observations from the Solar X-ray Monitor (XSM) onboard Chandrayaan-2 with particle flux measurements from multiple spacecraft, and by modelling the particle propagation event, we experimentally determine the SEP diffusion coefficient.

What controls the oxygen isotope–salinity relation in the northern Indian Ocean?

Date: 2025-11-25
Speaker: Dr. Arvind Singh
Venue: Ground Floor Lecture Hall

Abstract

Seawater oxygen isotopic composition (δ18O) and salinity show a near-linear covariance, forming the basis of widely used δ18O–S relationships. These relationships are often applied to reconstruct past salinity in the ocean from foraminiferal δ18O, yet the associated uncertainties can be large, with errors in inferred salinity reaching >50%. Much of this uncertainty stems from the limited availability of high-quality modern seawater δ18O measurements and an incomplete understanding of the processes that shape this relationship. In this talk, I will present a comprehensive modern seawater δ18O dataset generated at PRL, and discuss how it advances our understanding of the controls governing the δ18O–salinity relationship in the northern Indian Ocean.

Quasiclassical electron transport in topological Weyl semimetals

Date: 2025-11-20
Speaker: Azaz Ahmad
Venue: online link: https://imeet.vconsol.com/join/8617443886?be_auth=MDk0MzY2

Abstract

Weyl fermions bridge geometry, topology, and physics, appearing as excitations in Weyl semimetals (WSMs) with unique electronic properties. This seminar will explore chiral anomaly (CA) in WSMs, primarily through longitudinal magnetoconductance (LMC) and the planar Hall effect (PHE). While intervalley scattering is known to reverse LMC, we identify a new mechanism: a smooth lattice cutoff induces nonlinear effects leading to negative LMC. Using a tilted Weyl fermion model, we map phase diagrams to diagnose CA signatures [1]. Strain, acting as an axial magnetic field, introduces a ‘strong sign-reversal’ in LMC, distinct from external fields requiring intervalley scattering. The interplay of external and chiral gauge fields enriches LMC phase diagrams, and we predict distinct strain-induced features in PHE [2]. Extending to nonlinear transport, we develop a theory for the chiral anomaly-induced nonlinear Hall effect (CNLHE), revealing nonmonotonic conductivity in WSMs and a contrasting quadratic dependence in spin-orbit coupled metals [3]. Finally, we generalize CA to pseudospin-1 fermions, showing distinct transport signatures and enhanced sensitivity to internode scattering [4]. These findings provide a unified framework for diagnosing chiral anomaly in diverse chiral quasiparticles, guiding future experimental studies.

Monte Carlo Sampling for Wave Functions Requiring (Anti)Symmetrization

Date: 2025-11-18
Speaker: Dr. Ajit C. Balram
Venue: Theory seminar room no: 469

Abstract

"Many strongly correlated states, such as those arising in the fractional quantum Hall effect and spin liquids, are described by wave functions obtained by dividing particles into multiple clusters, constructing a readily evaluable wave function in each cluster, and (anti)symmetrizing across these clusters. We introduce a method to compute quantities such as energies and correlators, using Monte Carlo simulations for these states. Our framework overcomes the factorial scaling of explicit (anti)symmetrization, allowing for studies of systems beyond the reach of exact diagonalization.References: [1]. A. Ahmad et al., Phys. Rev. B 103, 115146 (2021). [2]. A. Ahmad et al., Phys. Rev. B 107, 144206 (2023). [3]. A. Ahmad et al., Phys. Rev. B 111, 035138 (2025). [4]. A. Ahmad et al., Phys. Rev. B 112, 045135 (2025). "

Random encounters in asteroseismology and their impact on a scientific career

Date: 2025-11-18
Speaker: Dr. Peter De Cat
Venue: 113/114, Thaltej Campus

Abstract

As a little boy, I was already fascinated by the magnificent light show of the twinkling stars in the night sky. My scientific career started almost 30 years ago when, as a physics student at KU Leuven (Belgium), I prepared my master's thesis under the supervision of Conny Aerts. Thanks to her enthusiasm, I started to look into asteroseismology, where the stars reveal the secrets of their hidden interior through the way they vibrate. In this presentation I would like to demonstrate how my interest in stellar pulsations in combination with a few random encounters have led to the two projects that I consider my greatest scientific achievements to date, namely the close collaboration with colleagues from both China (via the LAMOST-Kepler project) and India (via the BINA project). The strength of these projects will be demonstrated by some scientific results in different domains.

Long term X-ray Spectral study of Seyfert Galaxy Mrk 530

Date: 2025-11-17
Speaker: Priyadarshee P. Dash
Venue: 113/114, Thaltej Campus

Abstract

Active Galactic Nuclei (AGN) are among the most luminous astronomical sources, powered by accretion of matter onto a Supermassive Black Hole (SMBH). Their X-ray emission arises from the upscattering of optical/UV photons from the accretion disk by a hot corona of relativistic electrons, producing a power-law spectrum, which is modified by absorption and reflection features. In some AGN, an excess of photons above the standard power-law can be observed below the 2 keV energy range, termed as Soft Excess. The origin of this Soft excess is still a matter of debate, and various theories have been proposed to explain this excess emission. The warm corona model attributes this emission to arise from the inverse Comptonizaton of the disk photons in an optically thick, warm (0.1 - 1 keV) corona. Alternatively, the blurred ionized reflection scenario explains the soft excess to be a result of the relativistic blurring of the reprocessed emission from the disk due to the effects of strong gravity near the SMBH. More recently, hybrid models combining both warm Comptonization and ionized reflection components have also been proposed.

Supercurrent detection of Majorana-mediated quantum-phase transitions

Date: 2025-11-13
Speaker: Dr. Debika Debnath, PRL
Venue: Theory seminar room no 469

Abstract

"We study the experimental signatures of the quantum phase transition (QPT) through the supercurrent probed via scanning tunneling microscopy (STM) to a spin-polarized adatomic impurity which is embedded on a superconductor, giving rise to the non-degenerate Yu-Shiba-Rushinov (YSR) state. We consider the YSR as a controllable state by the adatom's rotational angles ($\zeta, \theta$) and the adatom is coupled to the two end-mode Majoranas. Recent work by Awoga et. al. [1] has shown that controlling the coupling between the YSR and Majorana states through the adatom rotation, can change the parity of the quantum states by modifying the effective ground state energies of both the YSR and Majoranas, which leads to QPT. However, high-precision measurements are elusive for the predictions of the QPT points. Therefore, in this work, we calculate the supercurrent through the YSR-Majorana coupled state and find the jump in the supercurrent at the topological QPT points (i.e. the critical YSR-Majorana coupling strengths), which establishes the supercurrent as an experimental signature of the QPT in our model superconducting junction. We have also investigated the effects of the strong tunnelling and finite temperature on the QPT via the supercurrent calculation. In addition, our result shows that control over the Shiba energy may induce a '0-\pi' phase transition to the topological supercurrent. References: [1] F. Pientka, L. Glazman and F. Von Oppen, Phys. Rev. B 88, 155420 (2013). [2] O. A. Awoga, I. Ioannidis, A. Mishra, M. Leijnse, M. Trif, and T. Posske, Phys. Rev. Res. 6, 033154 (2024)."

Seasonal Variability of Water Vapor Dynamics in the Semi-Arid Region of Western India - revelations from isotopic investigation at Mt. Abu, Rajasthan.

Date: 2025-11-11
Speaker: Mr. Virendra R Padhya
Venue: Ground Floor Lecture Hall

Abstract

This study presents the first continuous year-long measurement of stable isotopes (d18O, dD, and d-excess) in atmospheric water vapor over semi-arid western India. Continuous in-situ observations captured isotopic variations from daily to seasonal scales to identify key controlling processes. Temporal changes in vapor isotopes are governed by shifts in moisture sources and the influence of recycled moisture, producing a distinct seasonal isotopic baseline. A pronounced isotopic depletion precedes rainfall events by several days, suggesting its potential as a precursor to precipitation. A sharp isotopic transition observed in late April indicates a major shift in vapor source. The dominant moisture sources—northern and southern Arabian Sea, arid terrestrial regions of Iraq–Iran–Afghanistan–Pakistan, and the wetter eastern landmass of India and the Bay of Bengal—each impart distinct isotopic characteristics, enabling the identification of seasonal vapor origins and their hydrometeorological implications.

Different Ways to Calculate NLP Amplitudes of Scattering Processes

Date: 2025-11-11
Speaker: Shuvendu Roy, PRL
Venue: Theory seminar room no: 469

Abstract

The scattering cross-section serves as a bridge between theoretical predictions and experimental observations. However, from a theoretical perspective, the perturbative expansion of the scattering cross-section may break down near the threshold region of certain kinematic variables. To preserve its perturbative behaviour, resummation techniques are employed. There exists a complete resummation theory for LP terms, but not yet for NLP terms. Two approaches are available to compute NLP leading logarithms: the first extends the methods used for colour-singlet production, but this makes the calculation more complex. To avoid these complications, a new technique has been proposed based on the spinor-helicity formalism with shifted spinors. Its application to H + jet production will be reviewed in the discussion, with a short introduction to the previous method along with its disadvantages.

Broad-band temporal and spectral study of Blazars

Date: 2025-11-06
Speaker: Avik Kumar Das
Venue: 113/114, Thaltej Campus

Abstract

Blazars are the most powerful subclass of active galactic nuclei in which observed emissions are highly Doppler boosted and observable across the entire accessible electromagnetic spectrum ranging from radio to gamma-rays, with diverse variability timescales spanning across minutes to years. The AGN activity level appears to vary on various time-scales. To date, most of the studies have focused mainly on high activity episodes, thereby offering a limited view of the source physical conditions. In our recent work we studied long-term broadband temporal and spectral study of a TeV BL Lac object TXS 0518+211 using 16 years of simultaneous optical, UV, and X-ray observations. In this blazar we find the complex nature of jet-dominated emission processes and suggest for more than one emission zone contributing to the observed broadband spectral energy distribution (SED). In this talk, I shall also present the results based on the photometric and spectroscopic observations acquired from Mt. Abu telescopes.

Nitrogen fluxes and primary productivity in Archaean Ocean

Date: 2025-11-04
Speaker: Mr. Janaarthanan P A
Venue: Ground Floor Lecture Hall

Abstract

The most oxidised form of nitrogen - Nitrate (NO3⁻) - serves as an essential and often limiting nutrient for life in the modern well-oxygenated ocean. However, ~3 billion years ago (Archean eon) the Earth’s surface environment and oceans were largely deprived of oxygen. Nitrogen isotopic composition (δ¹⁵N) of sedimentary rocks of that time suggests ammonium (NH4+) dependent anaerobic nitrogen cycling. In an attempt to quantify nitrogen fluxes and productivity in such ammonium-based ecosystem, we have developed a numerical two-box model that simulates Archean nitrogen cycling under ammonium-dependent conditions. In this seminar I will be discussing the results of the model and evaluate the Archean nitrogen isotopic record.

Neutrino oscillations in the plane wave and wave packet formulations

Date: 2025-11-04
Speaker: Safana P Shaji
Venue: Theory seminar room no: 469

Abstract

Starting with the theoretical development of neutrino oscillations from plane wave to wave packet formulation, the talk aims to provide insight into the quantity of decoherence, which outlines the wave packet separation. The comparison of oscillated and decohered events is carried out through the lens of Jiangmen Underground Neutrino Observatory (JUNO) experiment, within which we delve into the mass hierarchy and theta12 sensibilities.

Resurrection of Elements in the Milky Way: A MCMC Recipe

Date: 2025-10-31
Speaker: Antariksha Mitra
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The formation and chemical evolution of the Milky Way are traced through the continuous cycle of stellar birth, death, and enrichment, wherein each generation of stars contributes to the resurrection of elements in the interstellar medium. In this work, we present a Monte Carlo Markov Chain (MCMC) framework developed to model the Galactic Chemical Evolution (GCE) of 83 isotopes spanning 32 elements, employing updated stellar yields. The MCMC approach enables efficient sampling of the complex, multi-dimensional parameter space governing the Galaxy’s star formation rate, initial mass function, and supernova contributions, thereby constraining these parameters against observed elemental abundance distributions. Our simulation reproduces the observed chemical trends across the various regions of the Milky Way, offering insights into the dynamic interplay between stellar nucleosynthesis and Galactic assembly. The results highlight how the ashes of long-dead stars continually reforge the building blocks of new generations: a recursive process central to both the chemical and structural evolution of our Galaxy.

Planetary Differentiation and Sample Analysis

Date: 2025-10-24
Speaker: Prof Amit Basu Sarbadhikari
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

After accretion from dust, gas, and rock colliding and sticking together, Planetary differentiation is the process by which a planet's molten materials separate into distinct layers. Following this early stage of planetary evolution, the differentiation process continues for billions of years and may still be ongoing today, owing to the internal dynamics of each planet. Over the past decade, planetary missions—especially to the Moon and Mars, as well as the growing number of recognized lunar and Martian meteorites — have provided transformational insights into the diversity, composition, and histories of planetary materials throughout the inner Solar System. Yet, despite these new insights, defining a reasonably simple set of criteria that provides some predictive understanding of planetary crustal development remains elusive. This talk will try to showcase the elusive characteristics of our understanding towards planetary evolution through the proxy of extra-terrestrial sample analysis.

On-sky characterization and performance verification of ProtoPol

Date: 2025-10-23
Speaker: Arijit Maiti
Venue: 113/114, Thaltej Campus

Abstract

ProtoPol is a medium-resolution echelle spectro-polarimeter developed for the PRL 1.2m and 2.5m telescopes at Mt Abu observatory, India. ProtoPol provides a spectral resolution in the range of âˆ¼0.4 - 0.75ËšA across various orders in the visible wavelength range of 4000-9600ËšA. On PRL 2.5m PRL telescope, an SNR of 10 is achieved for Vmag âˆ¼ 13.5 source in 1 hour of integration time, and its throughput is estimated to be âˆ¼6% including all the contributing factors such as atmospheric transmission, telescope reflectivity, instrumentâ€™s optics, CCD efficiency, etc. ProtoPol achieved a linear polarization accuracy â‰ˆ 0.1 âˆ’ 0.2% in 2 hours of integration time for a source with Vmag â‰ˆ 8. The instrumental polarization is determined to be around 0.1%. Several Science observation campaigns were conducted with ProtoPol to demonstrate the capabilities of the instrument. A sample of Herbig Ae/Be stars, classical Be stars, Symbiotic stars, and AGB/post-AGB stars were observed over the period of one and a half years for their spectro-polarimetry measurements covering various physical mechanisms such as line polarization in Herbig and classical Be stars, polarization in Raman scattered features in Symbiotic stars, as well as continuum polarization in AGB/post-AGB stars to verify the polarization performance of the instrument.

Coastal Groundwater: Effects of Climate Change and Abuse on a Critical Resource

Date: 2025-10-17
Speaker: Prof. Willard S. Moore
Venue: Ground Floor Lecture Hall

Abstract

Groundwater is an essential resource for most coastal communities. Abuse of this resource and global sea level rise due to climate warming endanger its sustainability. In this talk, I will discuss less obvious aspects of changing coastal groundwaters. Along some coastlines, excess groundwater mining leads to land subsidence. Combined with global sea level rise, this causes enhanced coastal flooding and saltwater intrusion (SWI) into coastal aquifers. The intrusion of seawater into these aquifers poisons an essential resource. The movement is not one-way. Coastal aquifers are an underground link between the land and sea. Terrestrial freshwater and seawater are constantly mixed and exchanged within these permeable sediments, called subterranean estuaries. The flow of fresh or salty groundwater into the ocean is called submarine groundwater discharge (SGD). SWI radically alters the groundwater chemistry by introducing sulfate, a major ion in seawater and a powerful oxidizing agent. Fresh groundwater has low oxidation capacity due to the low solubility of oxygen. The sulfate in seawater brings 200 times greater oxidation capacity, allowing considerably more carbon to be oxidized. The byproducts of marine carbon oxidation include CO2, nutrients (N, P), sulfide (H2S), dissolved organic carbon and nitrogen, and reduced metals (Fe2+, Mn2+). SGD transports these byproducts of carbon oxidation into estuarine and coastal waters, where they may stimulate biological productivity – sometimes to excess, and deplete dissolved oxygen concentrations through reactions with sulfide and other reduced substances. My focus in this talk will be on the interplay between SWI and SGD and the effects on estuarine and coastal waters. About the speaker: Prof. Willard S. Moore is Distinguished Faculty Emeritus in the School of the Earth, Ocean and Environment at the University of South Carolina, USA. He is an internationally renowned marine geochemist whose pioneering research has transformed our understanding of coastal and oceanic processes through the application of naturally occurring radioisotopes, particularly radium isotopes. Prof. Moore’s work has been instrumental in quantifying submarine groundwater discharge and assessing its role in the transport of nutrients, trace metals, and carbon to the coastal oceans. Prof. Moore has been elected Fellow of both the American Geophysical Union (AGU) and the American Association for the Advancement of Science (AAAS), and is a recipient of the prestigious “Buck” Ketchum Award from the Woods Hole Oceanographic Institution.

Exploring GRB Localisation Capability of Proposed Daksha Mission using Coded Mask Imaging with its Low-Energy Detectors and Their Development.

Date: 2025-10-16
Speaker: Ashish Kumar Mandal
Venue: 113/114, Thaltej Campus

Abstract

Gamma Ray Bursts (GRB) are short, intense extragalactic gamma-ray flashes. GRBs are of two kinds-long GRBs (burst duration >2 sec) thought to be produced due to core collapse of rapidly rotating massive stars, short GRBs (duration <2 sec) believed to be produced due to merger of binary compact objects like neutron star-neutron star (NS-NS) or black hole-neutron star (BH-NS). Daksha is India’s proposed high-energy transient mission aimed at detecting and characterizing electromagnetic counterparts (EMCs) of gravitational wave (GW) events and GRBs. In its initial configuration, Daksha can localize short GRBs to within 5–10 degrees using a projection method. Daksha’s scientific potential could be greatly enhanced if onboard GRB localization within 1 degree is made possible, which can be potentially achievable using the Coded Aperture Mask (CAM).

Multi-wavelength Variability and Quasi Periodic Oscillations (QPOs) in Blazars

Date: 2025-10-13
Speaker: Prof. Alok Gupta
Venue: 113/114, Thaltej Campus

Abstract

This is the age of multi-wavelength (MW) time domain astronomy in which the transient astronomical sources are of great interest due to their rapid change in flux, spectra and polarization. Simultaneous MW observation of a particular transient source over an extended period of time has importance to understand the emission mechanism in different electromagnetic (EM) bands. Blazars are among one of the most favourite astronomical transient objects, because they emit radiation in the complete EM spectrum, and their flux, spectra and polarization are highly variable.

Interplanetary Dust and Its Measurement in Solar System

Date: 2025-10-10
Speaker: Prof. Jayesh Pabari
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Our solar system is immersed in a thin cloud of Interplanetary Dust Particles (IDPs). The dust is an important constituent in formation of solar system and found everywhere. The IDP may originate from sources like Asteroid belt, Kuiper belt or comets and evolve dynamically under the influence of various forces. Although, there are some measurements of IDP near Earth and also, in the interplanetary space; there are no measurements of IDP at other inner planets. The entering dust particles in a planetary object can affect it in different ways. During the seminar, the results of IDP flux in inner solar system will be presented. The Dust EXperiment (DEX) was flown recently using POEM 3 on PS4 of PSLV C-58 (XPoSat) mission to understand dust particles in the Earth orbit. From the dust observations in near Earth orbit, the DEX was found working successfully in space. The results obtained from DEX will be also be presented

Search for dark matter over a wide mass range: using JWST and neutrino telescopes to search for non-gravitational signatures of dark matter

Date: 2025-10-10
Speaker: Dr. Ranjan Laha
Venue: Theory seminar room no: 469

Abstract

"I will discuss two different ways to search for dark matter (DM). First, I will discuss how we used JWST data to probe eV-scale QCD axion DM or axion-like particle (ALP) DM decaying into two photons. This will produce a distinct line signature in the spectroscopic observations made by JWST. Using the latest NIRSpec IFU spectroscopic observations from JWST, we put some of the strongest bound on the photon coupling for QCD axion/ ALP DM in the mass range between 0.47 and 2.55 eV. In the second part of my talk, I will discuss how neutrino telescopes like IceCube and Super-Kamiokande can probe DM - electron scattering. DM can get captured inside the Sun due to DM - electron scattering and it can annihilate into neutrinos and anti-neutrinos. Using latest neutrino measurements, we set world leading limit on DM - electron scattering for DM masses between 10 GeV to about 10^5 GeV."

Role of picophytoplankton in the carbon cycle of the northern Indian Ocean

Date: 2025-10-07
Speaker: Dr. Sipai Nazirahmed
Venue: Ground Floor Lecture Hall

Abstract

Picophytoplankton are vital drivers of marine biogeochemical cycles and serve as indicators of ocean productivity, ecosystem health, and climate change. As the smallest single-celled phytoplankton, they play a crucial role in ocean ecosystems, being globally recognized as major primary producers and significant contributors to the oceanic carbon stock. Despite their ecological importance, their role is often underestimated, particularly in the northern Indian Ocean—an oceanic region characterized by high environmental variability and dynamic biogeochemical processes. In this seminar, I will present the results that aimed to quantify the abundance and carbon biomass of picophytoplankton and to assess the influence of regional physicochemical parameters on their spatial distribution and ecological role in the northern Indian Ocean. Our findings demonstrate that the contribution of picophytoplankton carbon biomass to the total particulate organic carbon (POC) pool was substantial in both the Arabian Sea and the Bay of Bengal. This underscores their significant, yet often overlooked, role in supporting the regional biological pump and influencing carbon fluxes.

Improved Constraints on Coexisting WIMP/ FIMP Dark Matter and Primordial Black Holes

Date: 2025-10-06
Speaker: Dr. Prolay Krishna Chanda
Venue: Theory seminar room no: 469

Abstract

Particle dark matter and primordial black holes (PBHs) may coexist with significant cosmic abundances, each contributing to the observed dark matter density ΩDM. Large populations of PBHs with ΩPBH ∼ ΩDM are strongly constrained for masses above 10−11M⊙. If the WIMP/ FIMP particle dark matter has interactions with the Standard Model, new constraints arise due to pair-annihilations that are enhanced by the PBHs, resulting in dark matter indirect detection constraints on fPBH — these bounds rule out the mixed WIMP-PBH dark matter for velocityindependent cross-section, ⟨σv⟩ ∼ 10−26cm3/s. In this talk, we will discuss how a particle DM candidate with a velocity-dependent cross-section relaxes these bounds. We also derive the bounds on mixed scenarios in which PBHs coexist with particle dark matter whose relic abundance is set via freeze-in (‘FIMPs’). We show that while the restrictions on fPBH are less constraining for FIMPs than WIMPs, modest bounds still arise for large classes of models.

Investigating Lunar Subsurface Water Ice through Neutron Leakage and Gamma-Ray Continuum Flux

Date: 2025-10-03
Speaker: Ms Shipra
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Lunar volatiles, including water ice, are considered to be preserved in cold traps or buried beneath the surface layer near the poles. Understanding their distribution and abundance is critical for advancing knowledge of lunar evolution and for supporting future exploration activities. Neutron and gamma-ray spectroscopy provide key tools for this purpose, as subsurface hydrogen abundance can be inferred to depths of up to 1 m from measurements of neutron leakage flux and gamma-ray continuum flux from the Moon. In this seminar, I will discuss the lunar leakage neutron and gamma continuum flux induced by galactic cosmic rays interacting with the lunar surface, as well as their dependence on subsurface hydrogen abundances, using Monte Carlo simulations. The effects of temperature and compositional variation on neutron leakage flux are examined. The sensitivity of the leakage neutron intensity to the depth profile of subsurface water ice within the top 1 m of soil will also be discussed.

Geochemical Insights into the formation of Andaman Ophiolite during Subduction Initiation

Date: 2025-09-30
Speaker: Mr. G N S Sree Bhuvan
Venue: Ground Floor Lecture Hall

Abstract

Ophiolites are fragments of the oceanic lithosphere exposed on land. It is essential to understand the magmatic history of an ophiolite, which holds geochemical clues to its tectonic setting. Recent research on the Neo-Tethyan ophiolites suggests that the ophiolite formation is related to subduction, likely during subduction initiation. Andaman ophiolite, exposed on the forearc of the Andaman subduction zone in the Andaman Islands, India, is a dismembered ophiolite containing mantle peridotites, cumulate gabbros, intrusive plagiogranites, massive and pillow basalts, with later dyke intrusions. Although the age of the Andaman ophiolite is well constrained to be 98±8Ma, its formation remains debated, with views suggesting a diverse range of tectonic settings. Hence, it presents an opportunity to test the hypothesis of ophiolite formation during subduction initiation. Using bulk rock major and trace element abundances and Sr-Nd isotopic compositions, I will present new inferences on the origin of the Andaman ophiolite.

Stable and Interpretable Jet Physics with IRC-Safe Equivariant Feature Extraction

Date: 2025-09-25
Speaker: Deepanshu Srivastava, PRL
Venue: Theory seminar room no: 469

Abstract

"Deep (machine) learning has achieved remarkable success in the complex area of QCD (Quantum Chromodynamics) jet classification using low-level calorimeter data from high-energy physics detectors. However, a significant challenge persists: understanding what these models learn and how their features correlate with established QCD observables. Improving interpretability is essential for building robust and trustworthy machine learning tools in any of their applications. To tackle this challenge, we present a case study using graph neural networks for quark–gluon discrimination, systematically incorporating physics-motivated inductive biases. In particular, we design message-passing architectures that enforce infrared and collinear (IRC) safety, as well as additional symmetries, including E(2) and O(2) equivariance in the rapidity–azimuth plane. Using simulated jet datasets, we compare these networks to unconstrained baselines in terms of classification performance, robustness to soft emissions, and internal feature organisation. Our findings demonstrate that embedding symmetry and safety constraints not only improve robustness but also ground network representations in established QCD structures, providing a principled path toward interpretable deep learning in collider physics. "

Amplifying muon-to-positron conversion in nuclei with ultralight scalar dark matter

Date: 2025-09-22
Speaker: Dr. Purushottam Sahu
Venue: Theory seminar room no: 469

Abstract

"I will present an analysis of the lepton-number and lepton-flavour-violating process of muon-topositron conversion µ − +N → e + +N ′ , in the presence of an ultralight scalar dark matter (ULSDM) field which couples to neutrinos. The ULSDM contributes to the effective off-diagonal Majorana mass mµe, therefore amplifying the rate of muon-to-positron conversion to experimentally observable levels. Using existing bounds from SINDRUM II, COMET, and Mu2e experiments, we derive constraints on the flavour-off-diagonal couplings of neutrinos to ULSDM . Our work reveals that upcoming experiments can provide stronger sensitivity to these new couplings than bounds arising from cosmological surveys and terrestrial experiments.

MXene in LEO: A Technology Demonstration of Nano-Biomaterial Devices in the ISS with Axiom 4 Mission

Date: 2025-09-18
Speaker: Dr. Shreyas Srivatsa
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

MXenes are a family of two-dimensional nanomaterials made of metal carbides/nitrides/carbonitrides. The inorganic compound of MXenes, first reported in 2011 (titanium carbide, Ti3C2TX-MXene), has found various terrestrial applications like supercapacitors, sensors, electromagnetic shielding, chemical sensors, wearable devices, biomedical and implantable devices, multifunctional coatings, etc. Some of the unique properties of MXenes (particularly, Ti3C2TX-MXene) are film-forming ability, hydrophilic behavior, low electrical resistivity, good elasticity, field-electron mobility of, and fast dynamic response behavior. The possibility of hundreds of unique stoichiometric MXene combinations, reported to date, results in achieving wide tunability of physical and chemical properties by varying ratios of metal and carbide/nitrides/carbonitrides. After exhaustive testing and validation of the MXene devices in terrestrial environment, the speaker and his team were the first to test the MXene devices with several stratosphere flights from 2022. Building on the results from real environment testing of MXene nanomaterial and its devices, MXene in LEO (MXene Material and Wearable Device Experiments in Low-Earth Orbit Space Habitat) was proposed as part of the IGNIS mission of the European Space Agency and Polish Space Agency, forming a part of the Axiom 4 mission. MXene in LEO is a unique technology demonstration in the low-Earth orbit (International Space Station) using multifunctional nanomaterial (MXene) and sustainable biomaterial (bacterial cellulose) to form nano-biomaterial devices for human health monitoring in space. The first objective of the experiment was to test the environmental stability of MXene nanomaterial inside the space station. The second objective was to test the possibility of detecting hand movement and pulse of the human subject wearing the MXene wristbands in the space station. With the accomplishment of both objectives, the technology demonstrator provides a foreground for wider usage of MXene nanomaterials in space applications and their direct impact on terrestrial activities.

Looking under the lamppost for dark neutrino masses

Date: 2025-09-18
Speaker: Dr. Manibrata Sen
Venue: Theory seminar room no: 469

Abstract

The origin of neutrino masses remains one of the most pressing open questions in particle physics. While conventional approaches rely on extending the Standard Model with heavy fields or new symmetries, an alternative idea has recently emerged: neutrino masses may arise through refraction in the background of ultralight dark matter. In this framework, neutrinos acquire dynamic, effective, time-varying masses as they propagate through a coherent oscillating field, leading to distinctive imprints on oscillation experiments, beta-decay searches, and astrophysical neutrino signals. In this talk, I will introduce the basic mechanism of refractive neutrino masses and discuss its phenomenological consequences for laboratory, astrophysical, and cosmological probes and highlight how upcoming experiments may provide the first opportunities to test this novel connection between neutrinos and the dark sector.

Exploring Fluvial activity around the circum-chryse basin on Mars

Date: 2025-09-12
Speaker: Rishav Sahoo
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The Chryse Planitia is an asymmetrical basin centred at approximately 45oW and 24oN, about 2000 km northeast of Valles Marineris. It has a diameter of ~1600 km and is 2-3 km below the mean Mars elevation. This basin receives deposits from several major outflow channel systems. Two principal groups of channels terminate in this basin. The first originates from chaotic terrains near the eastern end of Valles Marineris and flows northward for over 1000 km into the southern part of the basin. This group includes Ares Vallis, Tiu Vallis, Simud Vallis, and Shalbatana Vallis. The second group, dominated by Kasei Vallis, enters the basin from the west. As such, Chryse Planitia receives sediment and water input from two widely separated source regions spanning over 2500 km. In this seminar I will discuss the interaction of the major fluvial channels with the rim of Chryse Planitia basin. I will be discussing a new method for estimating the discharge, volume and timescales of fluvial activities around the circum-chryse region. This new method involves simulation for Unsteady flow analysis through which I would be exploring one of the largest dam-break scenarios in the solar system.

Accelerator Mass Spectrometry - Current Understanding, Recent advancements and the way forward

Date: 2025-09-09
Speaker: Mr. A Shivam
Venue: Ground Floor Lecture hall

Abstract

Accelerator Mass Spectrometry (AMS) has revolutionized ultra-sensitive radio isotopic analysis across scientific disciplines. PRL Houses state-of-the-art 1MV Accelerator Mass Spectrometer for analysis of radioisotopes like 14C, 10Be and 26Al. This seminar explores the current understanding of AMS principles, highlights current status and recent developments in PRL-AURiS (PRL-Accelerator Unit of Radioisotope Studies) and the session will conclude with perspectives on future directions, exploring the possibilities of new isotopic targets, and broader interdisciplinary impact. Attendees will gain a comprehensive overview of AMS, its functioning principles, its evolving capabilities, and critical developments shaping the field. The seminar shall be in most general language - and shall be able to cater to a wide audience working in any field.

Linear and Nonlinear Excitations in Rotating Dusty Plasmas across Coupling Regimes

Date: 2025-09-08
Speaker: Dr. Prince Kumar
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Dusty plasmas consisting of dust particles, electrons and ions, can be found in various states of matter (solid, liquid, and gaseous) [1-3]. They, therefore, cover a broad range of parameter space relevant to both astrophysics as well as laboratory environments. Studies of the collective excitations in dusty plasmas provide valuable insights into their static and dynamic properties, as well as how these excitations can be controlled for practical applications [4-7]. For example, investigations of these excitations in the strongly coupled limit can be relevant to ion trap systems where the phonon mode spectrum is manipulated to enhance quantum gate performance efficiency [8]. From an astrophysical perspective, recent dusty plasma experiments have observed nonlinear excitations, such as pinned, precures solitons, generated by a moving charged obstacle [9]. These observations motivate the idea of indirect detection of space debris in the ionosphere through such structures[10]. In this talk, I first discuss magnetoplasmon excitations in rotating dusty plasma equilibria that can be generated in the absence of non-conservative fields [1-2]. These magnetoplasmon signatures have been observed in the absence of a real magnetic field across a wide range of dusty plasmas parameter [1]. Then, I address the nonlinear excitations such as Korteweg-De Vries (KdV) Soliton, pinned, precursor solitons in non-rotating dusty plasmas. The characterization of KdV Soliton structures is presented in details under the existing models to test their reliability, and new models are proposed to overcome their limitations [6-7]. Finally, I discuss the pinned and precursor solitons, which are induced in the medium by a moving charged source, appearing at and ahead the source, respectively, under specific Mach number values. The potential applications of these structures for detecting space debris in the lower Earth orbit (LEO) region of the ionosphere are also outlined.

From Suppression to Reprogramming: Precision Nanomedicine for Rheumatoid Arthritis and Beyond

Date: 2025-09-02
Speaker: Dr. Ashutosh Kuma
Venue: Ground Floor Lecture Hall

Abstract

Chronic inflammatory diseases, including rheumatoid arthritis and certain cancers, remain among the most challenging conditions to treat. Conventional therapies often work broadly across the body, suppressing the immune system in ways that can cause serious side effects and fail to provide lasting benefit. My lab is pursuing an altered path: nanomedicine designed to bring treatment directly to the source of inflammation. My lab engineer long-circulating lipid nanoparticles, including immunoliposomes, that selectively accumulate in inflamed tissues. These carriers allow us to deliver RNA-therapeutics like siRNA and miRNA, along with anti-inflammatory drugs, precisely where they are needed, reducing systemic toxicity and expanding the therapeutic window. This targeted approach not only calms harmful immune activity but also reprograms immune cells toward reparative states, offering the possibility of rebuilding tissue function rather than merely suppressing disease. Our work addresses multiple levels of immune regulation, including silencing key cytokines, modulating the NF-κB and JAK–STAT pathways, and investigating PAD inhibition to prevent early autoimmune triggers. Beyond treatment, the lab is developing early detection strategies to identify disease before irreversible damage occurs. By tracking biomarkers such as protein modifications driven by PAD enzymes, we aim to capture the earliest molecular signals of autoimmunity. At the same time, we are making efforts to integrate laboratory findings with retrospective patient data to understand how inflammation, comorbidities, and lifestyle factors shape treatment responses. Together, these efforts outline a translational roadmap that links mechanistic insight with clinical application.

Exploration of the Venus and Lunar Ionosphere Using Radio Science Experiments

Date: 2025-09-02
Speaker: Dr. Keshav R Tripathi
Venue: ONLINE

Abstract

Venus and the Moon, our two neighbouring celestial bodies, exhibit extreme contrasts in atmospheric conditions. Venus has a neutral density nearly 90 times that of Earth, while the Moon has an almost negligible atmosphere. Despite these differences, both bodies possess significant ionized layers capable of affecting radio signal propagation. This seminar will focus on the characteristics of these ionospheric layers as revealed through radio occultation experiments, with comparisons to Earth’s ionosphere. We will also discuss the implications of these findings for future exploration.

Chandrayaan-3 Pragyan Rover at Shiv Shakti Statio: Findings from APXS In Situ Geochemical Measurements and Contextual Remote Sensing Analysis

Date: 2025-08-29
Speaker: Dr. Rishitosh K. Sinha
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The Chandrayaan-3 mission is the first successful soft-landing at the Shiv Shakti statio (located at 69.37°S, 32.32°E) in the south polar region of the Moon. During the mission, the Pragyan rover traversed around 103 m on the lunar surface within a single lunar day. Onboard the rover was an instrument called the Alpha Particle X-ray Spectrometer (APXS), which measured the elemental composition of the Moon’s surface. The abundance measurements of major elements supported the widely accepted lunar magma ocean (LMO) hypothesis, which suggests that the early Moon was once covered by a global layer of molten material. In addition to major elements, the APXS also measured the abundance of volatile elements including sodium, potassium, and sulfur at the landing site, which varied in concentrations ranging from 700-2800 ppm, 300-400 ppm, and 900-1400 ppm, respectively. The detailed comparison and analysis of volatile abundances with the measurements in soil samples collected in earlier missions (Apollo 16 and Luna 20) revealed that there is anomalous depletion in sodium and potassium, but enrichment in sulfur in the soils at the Chandrayaan-3 landing site. One possible source of sulfur in lunar soils is Type I Carbonaceous chondrites (CC), which can add approximately 400-1000 ppm of sulfur into the lunar soil. However, this alone cannot explain the excess of 200-400 ppm sulfur observed at the Chandrayaan-3 landing site. In this case, there has to be another source of sulfur that increased its concentration at the landing site. Toward the end of the LMO crystallization stages, around 4.3 Ga ago, the residual molten layer in the lunar mantle became enriched in a mineral called Troilite (FeS), which contains sulfur. Around the same time, a giant impact created the South Pole-Aitken (SPA) basin, which is one of largest and oldest impact basins in the solar system, approximately 2,500 km wide. This massive impact likely excavated this sulfur-rich troilite from the Moon’s interior, when the KREEP (potassium, rare earth elements, and phosphorus) layer was not adequately formed. The subsequent impacts on SPA basin ejecta resulted in further stirring of the materials across the region, possibly redistributing it at the Chandrayaan-3 landing site. To summarize, the Chandrayaan-3 landing site hosts sulfur-rich material from the Moon’s primitive mantle, which was excavated by the SPA basin impact billions of years ago. This makes the Chandrayaan-3 landing site a valuable place for accessing samples from the mantle of the Moon, which is otherwise lacking in the existing lunar collections. These samples would offer a rare opportunity to study about the early evolution of the Moon.

New plasmon-like mode in PdTe2: Raman scattering and memory function study

Date: 2025-08-26
Speaker: Dr. Bharathi Ganesh D, PRL
Venue: THEPH Room no: 469 (seminar room)

Abstract

PdTe2 is a 2D material with its bands having a tilted Dirac cone structure. Due to its novel band structure it is touted to have many promising applications. Understanding the low energy excitation of such materials is important and in this direction we reported a new plasmon-like mode emerging at low temperatures (< 100 K) in PdTe2. We support this claim with a phenomenological analysis based on the memory function formalism.

Uranium in the ocean: Inferences on bottom water anoxia during the Last Glacial Period

Date: 2025-08-19
Speaker: Prof. Manmohan Sarin
Venue: Ground Floor Lecture Hall

Abstract

The paleo-oceanographic studies suggest that deep ocean was depleted in dissolved oxygen (O2) during the last glacial period (LGP, ~18 kyr BP). Therefore, paleoceanographers have sought a direct tracer for studying the changes in dissolved O2 in the deep ocean during the LGP. Geochemical proxies like redox-sensitive trace elements (Vanadium, Molybdenum, Uranium, Manganese) in bulk sediments have been used to reconstruct the past bottom water environment. Example, in oxic seawater, uranium is present in relatively high concentration as uranyl-carbonate complexes which are highly soluble. Under O2 deficient (anoxic) conditions, uranium can be reduced from U(VI) to a less soluble tetravalent state U(IV), which is particle reactive and gets fixed into the sediments. A geochemical study validating this concept was published in 1993 (‘Geochemical evidence for anoxic deep water in the Arabian Sea during the last glaciation’; Sarkar, Bhattacharya & Sarin; Geochimica et Cosmochimica Acta). The purpose of this seminar is to discuss two recent articles (Geochemical Perspectives Letters 2024 and Marine Geology 2025) using the very same concept/approach published more than three decades ago (PRL study).

Quantum mechanics, decoherence, and quantum-to-classical transition

Date: 2025-08-14
Speaker: Prof. Navinder Singh, PRL
Venue: Room no: 469 (Main Campus)

Abstract

This talk is divided into two parts: First part will be an elementary introduction to the theory of decoherence, quantum mechanics, and quantum-to-classical transition. We will discuss how Niels Bohr's idea of the "cut" and the requirement of a classical apparatus for the interpretation of quantum mechanics can be rationalized in the framework of the modern theory of decoherence by Zurek and others. In the second part, we present our results related to the Ovchinnikov-Erikhman theory of decoherence. We point out the problems with this scenario and revise it to apply it to a realistic case of the motion of conduction electrons. Interesting results are obtained. Our results agree with the alternative master equation approach.

Evolution of the Laxmi Basin, Arabian Sea, during the Deccan volcanism

Date: 2025-08-12
Speaker: Dr. Sibin Sebastian
Venue: Ground Floor Lecture Hall

Abstract

The Laxmi Basin is a prominent geomorphic feature and a marginal depression in the Northwest Indian Ocean (Arabian Sea). This ~300 km wide basin separates the western Indian continental margin from the Laxmi Ridge (LR), which is believed to be continental. The precise nature of the basin's basement remains controversial, with differing views suggesting it could be either a stretched continental crust with magmatic intrusions related to continental rifting (contemporaneous with Deccan volcanism) or a pre-Paleogene oceanic crust. Additionally, a geochemical study of the basin's igneous basement indicates that these rocks formed in a subduction zone setting. Understanding the crust's nature has implications for the geodynamic events of continental breakup and the formation of the Indian Ocean during the Late Cretaceous. To address this controversy, we conducted geochemical and isotopic studies on basaltic lava samples from this basement, recovered during IODP 355. In this talk, I will present the results of our study and our inferences regarding the crustal nature of the Laxmi Basin.

Lunar Polar Water-Ice: Current Understanding and New Insights from ShadowCam

Date: 2025-08-08
Speaker: Ms Sachana A S
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Our understanding of lunar volatiles is significantly improved using multi orbiter data-sets and reanalyzing returned samples. Multiple observational evidences suggest that water-ice is predominantly concentrated within permanently shadowed regions (PSRs) near the lunar poles, which are also the prime targets for future lunar exploration. With the current limitations of observational datasets, the occurrence, content, distribution and source of water-ice in PSRs are yet to be answered. In this work, we used ShadowCam, a high-resolution imaging system aboard the Korea Pathfinder Lunar Orbiter (KPLO) for understanding the PSR morphology. ShadowCam offers unprecedented views into these shadowed terrains, allowing detailed analyses of surface textures and reflectance anomalies that may indicate water-ice presence. Here, I will present the initial results from our analysis using ShadowCam data, investigating surface reflectance behaviour of PSRs from south pole, highlighting the reflectance variations that might indicate the distribution of water-ice at and within different PSRs.

NICER insight into the High-Energy Universe

Date: 2025-08-07
Speaker: Dr. Gaurava Kumar Jaiswal
Venue: 113/114, Thaltej Campus

Abstract

Since its deployment to the International Space Station in June 2017, the Neutron Star Interior Composition Explorer (NICER) has significantly advanced our understanding of compact objects in the X-ray sky. With exceptional timing and spectral capabilities in the 0.2 - 12 keV range, NICER enables detailed studies of accretion-powered and magnetically driven phenomena. A major focus has been on thermonuclear X-ray bursts -brief, intense explosions caused by unstable burning of hydrogen and helium on neutron star surfaces, which offer key insights into the physics of dense matter. This talk will highlight crucial findings from eight years of NICER observations, covering burst behavior, accretion dynamics, X-ray transients, and magnetar activities. It will also discuss efforts to understand the interaction between compact objects and their optical companions through X-ray and optical observations. Finally, I will present recent updates on the long-term calibration of the JEM-X instruments aboard ESA's INTEGRAL mission and ongoing progress toward establishing the INTEGRAL Legacy Archive.

An overview of compact X-ray binaries

Date: 2025-08-06
Speaker: Dr. Gaurava Kumar Jaiswal
Venue: 113/114, Thaltej Campus

Abstract

Compact objects represent some of the most extreme environments in the universe. When these dense remnants are part of a binary system, they can draw in matter from their companion stars through a process known as accretion. This transfer of material releases vast amounts of energy, making these systems strong sources of X-rays. Compact X-ray binaries, in which a neutron star or black hole accretes matter from a companion, offer unique opportunities to study energetic processes like accretion dynamics, outbursts, and thermonuclear bursts on neutron star surfaces. This talk will introduce the fundamental concepts behind accretion, compact binaries, and related phenomena, and will highlight why these systems are key to advancing our knowledge of high-energy astrophysics.

Nitrogen loss processes in aquatic ecosystems

Date: 2025-08-05
Speaker: Dr. KM Ajayeta Rathi
Venue: Ground Floor Lecture Hall

Abstract

Nitrogen, though abundant in the atmosphere, often limits primary productivity in aquatic ecosystems. These ecosystems play a crucial role in regulating the global nitrogen cycle both by converting inert atmospheric nitrogen into bioavailable forms through dinitrogen fixation and by removing excess reactive nitrogen via microbially mediated loss processes, including denitrification, anaerobic ammonium oxidation (anammox), and, to some extent, dissimilatory nitrate reduction to ammonium (DNRA). However, with increasing anthropogenic nitrogen inputs and climate-driven environmental changes, the efficiency and dominance of these pathways are shifting, with significant implications for ecosystem health, biogeochemical feedbacks, and nitrogen budgets. In this seminar, I will discuss the mechanisms, environmental controls, and experimental approaches used to study nitrogen loss processes in aquatic ecosystems.

Probing Compressed Inert Scalars with Forward Muon Tagging at the Muon Collider

Date: 2025-08-05
Speaker: Dr. Chandrima Sen, PRL
Venue: Room no: 469 (Main Campus)

Abstract

The compressed mass spectrum of the Inert Doublet Model (IDM) poses a significant challenge for current collider experiments, as the soft visible decay products and suppressed production rates hinder conventional search strategies. In this talk, I will explore the discovery prospects of such a compressed electroweak sector at a future high energy Muon Collider operating at 10 TeV. Focusing on vector boson fusion (VBF) production of inert scalar pairs, I will demonstrate how forward muon tagging provides a powerful handle to isolate signal events in scenarios where traditional missing energy based searches fail. After reviewing the relevant dark matter and experimental constraints on the IDM parameter space, I will present a detailed collider analysis using both cut-based methods and multivariate techniques. The impact of detector energy resolution will be discussed, highlighting the importance of precision instrumentation. Our results show that even in highly compressed and experimentally challenging scenarios, the clean environment and forward coverage of the Muon Collider can significantly enhance discovery potential, making it a compelling probe of dark sectors.

Advancing the Warm Calibration Unit for METIS on ELT: From Design Finalization to MAIT Phase

Date: 2025-08-04
Speaker: Dr. Vipin Kumar
Venue: 113/114, Thaltej Campus

Abstract

METIS, an advanced mid-infrared imager and spectrograph for the wavelength range 2.9-13.5 microns (astronomical L, M, and N-band), stands as one of the three science instruments at the Extremely Large Telescope (ELT). It will provide diffraction-limited imaging, coronagraphy, high-resolution integral field spectroscopy, and low and medium-resolution slit spectroscopy. Within the collaborative international METIS consortium, the University of Cologne is responsible for the design, manufacturing, and integration of the Warm Calibration Unit (WCU) of the instrument. The main role of WCU is to provide a stable and controllable reference signal to METIS that will allow troubleshooting and calibrating the response of METIS in various observing modes. In this talk, I will present the key requirements from METIS that drive the design of the WCU, followed by an overview of its optical and opto-mechanical design, and functional role within the instrument. The final part of the presentation will focus on the current status of the Manufacturing, Assembly, Integration, and Testing (MAIT) phase, including a brief discussion on the alignment verification plans for the offner relay optics of WCU.

Recent boulder falls on Planetary bodies: Insight into recent activities

Date: 2025-08-01
Speaker: Dr. S Vijayan
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Rockfalls or boulder falls on Earth are very common and occur almost daily in certain parts of the world. In contrast, rockfalls on Mars are rare, and no rockfalls have been reported on the Moon in the last decade. This difference underscores the value of studying boulder falls on planetary bodies, as they provide important insights into geological processes. On planetary bodies like Mars and the Moon, millions of boulders/rocks are present on the surface, formed through the weathering of the crust, impact breccia’s, and other geological processes. These boulders vary in size, ranging from a few meters to several tens or even hundreds of meters. On the Moon, these boulders are particularly abundant. To date, using the latest high-resolution images from the Chandrayaan-2 Orbiter High-Resolution Camera (OHRC) and Lunar Reconnaissance Orbiter Narrow Angle Camera (LRO-NAC) there is no report of recent movement of even a single boulder over the past decade. This brings an intriguing question: do all the boulders on the Moon have reached equilibrium, or have there been movements in the last few decades to centuries, which is not been detected to date? How does the detection of movement of boulders help in understanding the recent activities? In this presentation, I will provide evidence for recent boulder falls and their hotspot regions on the Moon related to seismic activity/moonquakes, impact-generated surface shaking, and thermal weathering. Aside from very recent impacts, the primary activity observed on the Moon over the past few decades to centuries is the boulder falls. With the newly identified boulder falls, the Moon joins Earth and Mars, with records of recent boulder falls driven by multiple sources suggesting a sporadically active Moon. Such regions could be potential landing sites for future missions to understand the recent surface/subsurface activity on the Moon.

Broad-band study of the SMC pulsar RX J0032.9-7348 during its X-ray brightening in 2024

Date: 2025-07-31
Speaker: Dr. Birendra Chhotaray
Venue: 113/114, Thaltej Campus

Abstract

Accretion-powered X-ray pulsars (XRPs) are magnetized neutron stars that are part of X-ray binary (XRB) systems. The XRPs emit X-rays by accreting mass from their binary companion. These pulsars are characterized by intense magnetic fields, typically ranging from ~ 10^12-10^14 G, which direct the infalling material toward their magnetic poles, where most X-ray photons are generated. When the magnetic and spin axes are misaligned, the resulting emission is observed as pulsations from the neutron star. RX J0032.9-7348, an X-ray transient, was first detected by ROSAT in 1993; however, its properties are largely unknown. After years of inactivity, the source entered an X-ray bright phase in 2024. We observed it during this phase using NuSTAR and NICER. In this talk, I will present the timing and spectral properties of RX J0032.9-7348 during its 2024 outburst and discuss our ongoing and future work.

Genesis of uranium mineralization in the Singhbhum Shear Zone: constraints from geochemistry and geochronology of hydrothermal minerals

Date: 2025-07-29
Speaker: Dr. Sarita Patel
Venue: Ground Floor Lecture Hall

Abstract

The genesis of uranium mineralization in the Singhbhum Shear Zone (SSZ), including the sources of the hydrothermal fluids has consistently remained a subject of debate. The present research deals with the Mohuldih and Bagjata uranium mine along the SSZ, India. The chemical and isotopic studies on the accessory minerals such as tourmaline, magnetite, fluorapatite, and monazite from the aforementioned mines were conducted to understand the mineralizing history in the Singhbhum Shear Zone. This discussion will focus on the distinct hydrothermal events and associated mineralization processes, as inferred from chemical compositions, isotopic signatures, and age data.

Census and Characterization of Hot and Variable Stars in Star Clusters

Date: 2025-07-28
Speaker: Dr. Arvind K. Dattatrey
Venue: Online

Abstract

Hot and variable stellar populations in star clusters such as blue straggler stars (BSSs), blue lurkers, horizontal branch (HB) stars, and white dwarfs (WDs) offer critical insights into stellar evolution, binary interaction mechanisms and the dynamical evolution of stellar systems. In this talk, I will shed light on the characteristics and formation pathways of these non-canonical stars with a few case studies. I will discuss the detection of extremely low-mass white dwarfs (ELM WDs) as companions in BSS binary systems in Globular cluster NGC 362. In NGC 362, the radial distribution of BSSs exhibits strong central concentration, classifying the cluster as dynamically evolved and likely in a post-core-collapse phase. We also report the first identification of blue lurkers in a globular cluster. Two-component SED modeling reveals their companions to be low-mass and ELM WDs with short cooling ages (< 4 Myr), suggesting a recent formation event likely triggered by dynamical interactions during core collapse. In addition, we identify high-mass WDs in NGC 362, which may have originated via white dwarf–white dwarf mergers, a rare but theoretically predicted evolutionary channel in dense stellar environments. In the open cluster NGC 2420, four binary systems were identified, including two BSS binaries, one BSS–ELM WD system, and one HB–ELM WD system. These systems are consistent with formation via Case A/B mass-transfer pathways, indicative of stable binary evolution in low-density environments. Ongoing time-series photometric analysis has led to the identification of multiple variable stars, including pulsating and eclipsing systems, particularly among the BSS and HB populations. These variables provide independent diagnostics of internal stellar structure, angular momentum evolution, and rotational modulation. I will also discuss the ongoing spectroscopic analysis of BSS–RGB binary systems to further constrain the mass-transfer origin of BSSs, for understanding the role of binary evolution in shaping the hot stellar populations observed in star clusters.

Probing Parent Body Processing Through the Spectral Signatures of Insoluble Organic Matter in CM Chondrites

Date: 2025-07-25
Speaker: Ms. Shreeya Natrajan
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

CM carbonaceous chondrites are time capsules preserving a complex history of aqueous alteration and thermal processing on their parent bodies. In this seminar, I will discuss how spectroscopic analysisof insoluble organic matter (IOM) from a wide suite of chondrites reveals temperatures (35–90°C) and duration of alteration. The variation in our estimates point towards multiple generations of organic matter, reflecting heterogeneity in parent body processes. Interestingly, some samples point to brief alteration events, while others hint at complex histories involving larger parent bodies or rubble-pile assemblies. These findings allow us to better understand the conditions under which primitive organic matter evolved in early solar system bodies.

Chemical compositions of the Ganga, Yamuna, Narmada and Tapi Rivers: An assessment of spatial and temporal variability

Date: 2025-07-22
Speaker: Dr. Rakesh Kumar Tiwari
Venue: Ground Floor Lecture Hall

Abstract

Rivers are the major pathways which supplies metals from the continents to the oceans. The chemistry of these pathways plays a crucial role in riverine systems as they influence water quality and terrestrial biogeochemistry. Further, their riverine supply to ocean is crucial in regulating ocean productivity, influencing the oceanic biological pump, which modulates the atmospheric CO2 levels and global climatic variability. In this talk I will present a detailed investigation of the elemental chemistry in seasonally and spatially resolved samples from the Ganga, Yamuna, Narmada and Tapi rivers.

Lepton Flavor Universal New Physics in B-Decays?

Date: 2025-07-22
Speaker: Dr. N Rajeev, PRL
Venue: Room no: 469 (Main Campus)

Abstract

"The flavor-changing neutral current (FCNC) semileptonic decays of B mesons offer a powerful avenue to indirectly probe New Physics (NP) beyond the Standard Model (SM). I will review the current status of the so-called B anomalies. While lepton flavor universality (LFU) ratios such as RK and RK∗ are in good agreement with SM predictions, notable deviations persist in individual branching fractions—for instance, B(B+ → K+μ+μ−) and B(B+ →K+e+e−), both of which deviate at the 4 − 5σ level. Additionally, the angular observable P'5 in B → K∗μ+μ− exhibits a 3.3σ deviation, and a 3.6σ discrepancy is reported in B(Bs → φμ+μ−). Although the recent measurement of Rφ is consistent with the SM, the individual branching fractions remain at odds with expectations. These persistent anomalies hint at NP contributions in both muon and electron sectors. Given that experimental bounds on b → see transitions are still relatively loose, NP might also manifest in the first-generation lepton sector. Motivated by these observations, we perform a global analysis of dimension-6 SMEFT operators, considering the possibility of NP contributions not only in b → sμμ transitions but also in b → see transitions."

Characterizing AGN and dual AGN duty cycles in SMUGGLE isolated merger simulations

Date: 2025-07-17
Speaker: Mr. Jay Motka
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Observational data show strong correlations between the mass of supermassive black holes and the properties of their host galaxies, leading to the idea of SMBH-galaxy co-evolution. Galaxy mergers are interesting events as gravitational torques during mergers drive gas towards galactic nuclei, which can enhance AGN activities. This leads one to question: to what extent do mergers enhance AGN activities compared to isolated galaxies, and how does this impact the galactic environment? In this talk, I shall elaborate on our efforts to answer this question by introducing Stars and MUltiphase Gas GaLaxiEs (SMUGGLE), a framework based on the hydrodynamic code AREPO with a multiphase interstellar medium. I shall talk about the limitations of traditional simulations, improvements in SMUGGLE, and other simulation specifications. Our efforts in characterizing the duty cycles of AGNs and dual AGNs during mergers have shown that Multiphase ISM in SMUGGLE yields highly variable accretion rates with short duty cycles. In mergers, the mean active phase timescales are in the order of 0.1 Myr to 1 Myr, and dual AGNs seem to be active for 10-20 per cent of the simulation time before the black holes merge. Differences in black hole masses, galaxy morphologies, and wind speeds do show a significant impact on AGN and dual AGN activities. I shall conclude with a summary of current results, as well as ongoing and future work.

On the T-linear resistivity of cuprates: theory

Date: 2025-07-14
Speaker: Prof. Navinder Singh, PRL
Venue: Room no: 469 (Main Campus)

Abstract

"By partitioning the electronic system of the optimally doped cuprates in two electronic components: (1) mobile electrons on oxygen sub-lattice; (2) localized spins on copper sub-lattice, and considering the scattering of mobile electrons (on oxygen sub-lattice) via generation of paramagnons in the localized sub-system (copper spins), we ask what should be the electron-paramagnon coupling function Mq so that T-linear resistivity results both in the low temperature limit (kBT << ~ωqcut) and in the opposite high temperature limit (qcut is a characteristic paramagnon cut-off wave vector). This ’reverse engineering approach’ leads to |Mq| scaling inversely with wave vector. We comment how can such exotic coupling emerge in 2D systems where short range magnetic fluctuations resides. In other words, the role of quantum criticality is found to be crucial. And the low temperature T-linear behaviour of resistivity demands that the magnetic correlation length scales as ξ(T) scales as 1/T which seems to be a reasonable assumption in the quantum critical regime of cuprates (that is, near optimal doping where T-linear resistivity is observed). "

The Role of Deformed Craters in Understanding Fault Kinematics and Geometries

Date: 2025-07-11
Speaker: Dr. Kimi Khungree Basumatary
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Understanding subsurface faults is inherently challenging, especially on planetary bodies where direct field observations are not possible. Numerous studies have relied on high-resolution imaging, topographic data, and numerical simulations to analyze surface features such as wrinkle ridges and lobate scarps, which are expressions of underlying thrust faults on the Moon, Mars, and Mercury. These surface morphologies reflect a range of fault geometries, including buckle folds, fault-bend folds, and backthrusts, though no consensus exists on their exact subsurface structures. Fault-controlled deformed craters—impact craters modified by fault movement—offer an alternative means of inferring fault orientation, displacement, and dip. Prior studies have used crater wall exposures and rim circularity to estimate fault parameters, but these approaches face limitations when traces are confined to crater walls or when craters are circular. To address this, we developed a method that applies to both crater walls and floors and accommodates various crater shapes. In my talk, I will present the methodology and results in detail.

Sediment Connectivity in India’s Large River Basins under Climate and Human-Induced Stress

Date: 2025-07-08
Speaker: Dr. Abhishek Dixit
Venue: Ground Floor lecture hall

Abstract

Currently, large river systems are under increasing stress due to climate-driven extreme events, floods, human interventions, and concerns over delta sustainability. These systems span diverse geomorphological, climatic, and lithological domains, each contributing uniquely to the basin’s sediment dispersal processes. These domains are activated or suppressed in response to external forcings such as climate extremes and human activities. In this talk, I will discuss these factors in the context of three major Indian river basins: the Brahmaputra, the Ganga, and the Godavari. I will show how the alluvial plains, particularly in the Ganga and Brahmaputra basins, may be highly sensitive to seasonal-scale fluctuations, which in turn influence sediment budgets and provenance signals. At the same time, climate-driven extreme events are leaving far-reaching and persistent imprints, with sediment signals traceable as far downstream as the Bengal delta. I will also explore how human interventions, particularly dams, have disrupted sediment connectivity within these river systems. Almost all of the observed reduction in sediment load can be attributed to reservoir storage, placing parts of the delta at risk of sinking. In conclusion, while climate-driven forces are significant, human-induced interventions are leaving equally, if not more, profound imprints on the sediment dynamics of India’s large river systems. A carefully integrated methodological approach is essential to effectively address these complex interactions.

Mineralogical Characterization of Mare Australe: A Unique Region on the Moon

Date: 2025-07-04
Speaker: Dr. Neha Panwar
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Mare Australe (47.77°S, 91.99°E) is a volcanic province ~1000 km in diameter at the eastern nearside and farside boundary of the Moon. It consists of 248 mapped basaltic patches arranged in a more-or-less circular pattern. Initially classified as a “distinct” basin, it was later considered a “no topographic basin” due to a lack of identifiable topographic features. The results from the GRAIL mission, did not confirm the presence of a basin coinciding with the previously proposed one. Instead, GRAIL suggested the presence of a ~880 km diameter impact structure northwards named the Australe North Basin centered at 35.5°S, 96°E. In the earlier study geological evidences were provided to further establish the presence of the Australe North Basin. Volcanic activity at Lacus Solitudinis and Bowditch Crater, once thought to be isolated, is now linked to Australe North Basin. Based on the re-defined basin boundaries in the region a significant part of Mare Australe’s basalts lie outside the boundaries of Australe North. These basaltic units of Mare Australe remain largely uncharacterized. In this seminar, I will present a detailed investigation into the mineralogical diversity of the Mare Australe region. This study aims to shed light on the nature and origin of the distinctive style of volcanism in the region, highlighting the unique geological setting of Mare Australe and its implications for lunar volcanic evolution.

Atmosphere Characterization of the Hot-Jupiter Exoplanets

Date: 2025-07-03
Speaker: Dr. Soumya Sengupta
Venue: ONLINE

Abstract

Hot Jupiters, tidally locked to their host stars, exhibit extreme day–night temperature contrasts that drive vigorous atmospheric circulation. In my recent work, I analytically and numerically quantified how this heat redistribution shapes their temperature–pressure (T–P) profiles and dayside emission spectra. Using discrete space theory radiative transfer simulations, I demonstrated that reduced heat redistribution leads to hotter daysides, stronger thermal inversions, and higher emission fluxes. Application to exoplanet XO-1b revealed near-complete heat redistribution, resolving key degeneracies in its atmospheric characterization. Beyond circulation, my research also addresses two crucial aspects: • Radius Inflation: Ionized atmospheric flows coupled with magnetic fields generate Ohmic dissipation within the radiative and convective zones. MESA evolutionary simulations, parameterized by atmospheric flow velocities, successfully reproduce the observed inflated radii of hot Jupiters through this internal heating mechanism. • Spectral Separation: I have generalized Chandrasekhar’s diffuse reflection theory to unify thermal emission and scattering, allowing precise separation of planetary spectra from stellar contamination in ultra-hot Jupiters. In future work, I plan to integrate equilibrium and non-equilibrium chemistry into circulation models to better capture day–night variations in chemical abundances to study the effect of atmospheric heat redistribution on the atmospheric chemistry and finally its imprints on the emission spectra. Additionally, I aim to extend these frameworks to lower-mass, potentially habitable tidally locked terrestrial planets to inform climate and habitability studies. I also plan to develop improved radiative transfer tools that can simultaneously handle complex emission, scattering, and chemical processes, providing stronger predictive power for upcoming JWST and ARIEL observations.

Palaeoceanographic implications of single planktonic foraminiferal isotopic analysis

Date: 2025-07-01
Speaker: Dr. Sanchita Banerjee
Venue: GFL

Abstract

Planktonic foraminifera have the ability to archive geochemical signatures of seasonal scale due to their short life spans. We utilized stable isotopes in individual foraminiferal tests to reconstruct sur-face ocean conditions and climate fluctuations over the past few thousand years in the Northern In-dian Ocean. We developed a state-of-the-art methodology for measuring the clumped isotope com-position (Δ47) of individual foraminiferal tests, marking the first such attempt. This approach holds the potential to reconstruct past ocean temperatures, offering unprecedented insights into short-term climate dynamics. We also analyzed δ13C and δ18O isotopic ratios in single foraminifera to resolve vertical habitat signals and understand the variation in mixed layer depths. These multi-isotope da-tasets allow us to better understand the physical and chemical structure of the upper ocean and its response to past climate change. In this talk, I will present preliminary results from this novel single-foram clumped and conventional isotope analysis, and discuss their implications..

Towards understanding lunar hydration using Chandrayaan-1 and Chandrayaan-2 NIR spectrometers

Date: 2025-06-27
Speaker: Dr Megha Bhatt
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The Moon Mineralogy Mapper (M3) onboard Chandrayaan-1 has been extensively utilized to map the global surface composition and detect OH/H2O on the lunar surface. It was the first instrument to systematically detect and map the 3-µm absorption feature associated with hydration, using observations acquired at different times of the lunar day. However, the compositional dependencies and temporal variability of this feature, especially in the polar regions, remain poorly understood. Moreover, M3’s limited spectral coverage—extending only up to 3.0 µm—restricted its ability to fully characterize the hydration feature and to distinguish between OH and H2O. The Imaging InfraRed Spectrometer (IIRS) onboard Chandrayaan-2 addresses this limitation by extending the spectral range to 5.0 µm, thus enabling discrimination between OH and H2O signatures. However, IIRS data also come with certain limitations that must be carefully understood before it can be reliably applied at the global scale. In this talk, I will present our i ndependent methodology for processing IIRS data in parallel with M3, aimed at achieving cross-calibration and a robust comparison of hydration features. We have selected multiple overlapping IIRS observations, including well-characterized landing sites, and categorized them based on lunar local time to study diurnal variations. After applying dark current subtraction, radiometric correction, and thermal emission modeling, the IIRS spectra were geometrically aligned with M3 and corrected for topographic and photometric effects. I will share our preliminary results, insights gained from the IIRS data processing workflow, and our outlook for integrating IIRS and M3 data in a comprehensive global-scale analysis.

Factors affecting gas-particle partitioning of the NHx system

Date: 2025-06-24
Speaker: Ms. Chandrima Shaw
Venue: Ground Floor Lecture Hall

Abstract

Ammonia (NH3) and its particulate form ammonium (NH4⁺) together form the reactive nitrogen system NHx, which plays a key role in air quality, particulate matter formation, and nitrogen deposition. The gas-particle partitioning of NHx is influenced by several factors like meteorology (temperature and relative humidity) and atmospheric chemistry (pH and aerosol liquid water content (ALWC)) with a complex interplay between them. While low temperature and high RH promote the partitioning towards the particulate phase, higher temperature shift it back to the gas phase. Aerosol pH and ALWC further control this balance, by governing the effect of this partitioning on PM load. While pH and ALWC influence the partitioning of gases into their particulate counterparts, this partitioning in turn affects the aerosol pH, creating a two-way interaction between chemical composition and aerosol thermodynamics. Given the multifaceted importance of the NHx system, it is essential to understand how meteorology and aerosol chemistry together, shape the gas-particle partitioning. This seminar aims to provide a deeper insight into the gas-particle partitioning dynamics of NH3 and NH4+, focusing on the role of temperature, RH, pH, and ALWC under different conditions.

Cosmogenic Nuclides in Meteorites: Constraining Cosmic Ray Exposure and Terrestrial Ages

Date: 2025-06-24
Speaker: Dr. Satvika Jaiswal
Venue: ONLINE

Abstract

Cosmogenic nuclides, produced by interactions between cosmic rays and meteoritic matter, are powerful tools for determining the cosmic ray exposure (CRE) ages and terrestrial residence times of meteorites. This talk will highlight the combined approach using Accelerator Mass Spectrometry (AMS) along with Noble Gas Mass Spectrometry (NGMS) to estimate both CRE and terrestrial ages. The talk will discuss how radionuclides such as ¹⁰Be, together with stable noble gases like ²¹Ne, help reconstruct the exposure history, shielding conditions, and delivery mechanisms of meteorites. These methods play a key role in understanding the journey of meteoroids from space to Earth and contribute toward developing robust AMS measurement protocols at PRL.

"Modeling Superconductivity, Magnetism, and Quantum Phenomena in Complex Materials"

Date: 2025-06-24
Speaker: Dr. Smritijit Sen, University of Florence
Venue: Online--- https://imeet.vconsol.com/join/4438320547?be_auth=MjE2MTAy

Abstract

We present a comprehensive exploration of quantum materials through state-of-the-art theoretical and computational techniques. Focusing on superconductivity, we delve into intra- and interband pairing mechanisms via Eliashberg formalism and model Hamiltonians, examining how pressure and doping drive Lifshitz transitions. The impact of magnetic impurities on superconducting states is analyzed using density functional theory (DFT) and Green’s function methods with potential applications in developing robust qubit platforms for quantum computing. We further investigate electronic structures through band dispersion, Fermi surfaces, and density of states to interpret experimental probes such as ARPES and IETS. We also highlight structure-property correlations under thermal perturbations, advanced crystal structure prediction using evolutionary algorithms like USPEX, and ongoing work on the optical and photocatalytic properties of mixed anionic systems, including thio-apatites with potential for solar-driven hydrogen production.

Concentrations of Hydrogenated, nitrogenated, & protonated sulfuric acid ions due to GCR (Galactic Cosmic Rays) impact ionization in lower atmosphere of Venus.

Date: 2025-06-20
Speaker: Ms Aastha Kumayu
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Solar radiation interacting with the Venusian atmosphere produces two prominent ionization layers: V2 (~140 km) and V1 (~125 km). However, due to the high atmospheric density, only Galactic Cosmic Rays (GCRs) can penetrate into the deeper layers of the Venusian atmosphere. As cosmic ray air showers propagate through the Venusian atmosphere, they develop extensively until reaching a maximum, typically located between 60 and 70 km, below this altitude, the flux of secondary particles steadily declines due to their insufficient energy to sustain ionization. Previous studies have theorized the ion-pair production rates in this region with negligible focus on ionic species responsible. This presentation will begin with a general overview of the Venusian atmosphere, followed by a concise explanation of the methodology and chemical model we have used to compute electron densities and ion concentrations for 74 ion species in this region. The talk will conclude with a discussion on of some of the dominant ions identified in the lower region, for example hydrated hydronium ions and hydrated ions of NO2-, CO3-.

Observing Solar Flares with SUIT: A New Window into the Near-Ultraviolet Sun

Date: 2025-06-19
Speaker: Soumya Roy
Venue: Online

Abstract

Solar flares are among the most energetic phenomena in the solar system, driving rapid restructuring of magnetic fields and heating across the solar atmosphere. While much progress has been made in understanding flares through observations in X-rays and extreme ultraviolet (EUV), the near-ultraviolet (NUV) range remains relatively unexplored—despite its sensitivity to key layers like the lower chromosphere and upper photosphere, where much of the flare energy is deposited. The Solar Ultraviolet Imaging Telescope (SUIT), onboard India’s Aditya-L1 mission, is the first instrument to provide full-disk solar imaging in multiple NUV passbands, opening a new window into this critical regime. In this talk, I will first outline the current state of flare research and highlight the observational and diagnostic gaps that exist in the NUV. I will then introduce SUIT’s science objectives in the context of these challenges. As part of my PhD, I contributed to the initial design of SUIT. I will also present our first results from SUIT, and discuss how these data can inform models of chromospheric heating and flare energy transport. This work sets the stage for SUIT’s long-term contribution to high-cadence, multi-height solar flare studies.

Probing collective response in the quantum system using Raman scattering

Date: 2025-06-17
Speaker: Dr. Surajit Sarkar, CEA Grenoble, France
Venue: Online---https://imeet.vconsol.com/join/8046909791?be_auth=NDgyMTQy

Abstract

"Raman scattering is an inelastic light scattering process in which energy is transferred from incident light to the system, and the strongest signal often appears in the absorption spectrum from the collective mode present in the quantum system. In the first part of the talk, I will present a novel effect arising from inversion symmetry broken spin-orbit coupling (SOC) on charge collective modes, plasmons, and how this could be studied using electronic Raman scattering. I will discuss that isolated plasmons could be strongly prominent in resonant eRS in the presence of spin momentum locking SOC in BiTeI, which were invisible previously due to standard $q^2$ suppression, where $q$ is the momentum transferred by the light. The last part of the talk is on Raman response in superconductors. Here, I will discuss the electronic Raman response (eRS) of multiband SC in both A1g and B1g channels across the time reversal symmetry broken transition and the potential possibility of Leggett and Bardassis-Schreiffer modes in the observed spectrum, depending on the nature of the ground state. We will also see from our results that eRS could be used as a probe to detect spontaneously broken time reversal symmetry of superconductors such as s+is and s+id states."

Multi-mode study of exotic stellar populations in dense stellar systems

Date: 2025-06-12
Speaker: Gaurav Singh
Venue: Online

Abstract

I will present a systematic study of exotic stellar populations-Blue Stragglers (BSS) and Extreme Horizontal Branch (EHB) stars-in dense environments of the Milky Way and satellite dwarf galaxies. Despite decades of research, their formation channels, binary companions, and chemical evolution remains poorly understood due to their diverse properties across different environments. These UV-bright objects have now become accessible through new facilities like AstroSat/UVIT and public catalogs, revealing previously unknown extreme systems that challenge existing stellar models. To resolve these puzzles, I propose a coordinated multi-wavelength campaign utilizing high and medium-resolution spectroscopy (ground-based optical/infrared observatories), UV diagnostics (HST, UVIT/AstroSat, Swift/UVOT), and astrometry (Gaia and HST). This approach will uncover binary interactions, atmospheric anomalies, and evolutionary pathways-providing critical insights into stellar rejuvenation mechanisms and revealing new characteristics of these stellar populations.

Farside Volcanism on the Moon: A Remote Sensing Perspective

Date: 2025-06-06
Speaker: Ms Tvisha R. Kapadia
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Volcanism on the Moon is primarily manifested in the form of mare basalts, which cover ⁓17% of its surface. Mare basalts exhibit significant compositional diversity and are mainly concentrated within and adjacent to the large circular impact structures, and have a total volume estimated at ~107 km3. Interestingly, the distribution of mare basalts is highly asymmetric, whereby the nearside hosts extensive basaltic emplacements and the farside exhibits remarkably fewer mare basalts. In my talk, I will be providing a detailed account of how the understanding of this fundamental dichotomy has evolved from the first glimpse of the farside by Luna 3 in 1959 to present-day (with missions like Clementine, Lunar Prospector, LRO, Chandrayaan, Kaguya, GRAIL, Chang’e). Despite these advances, key questions remain unanswered on the nearside-farside dichotomy in volcanism. I will discuss the existing gaps in the knowledge and the objectives of my thesis. The talk will conclude with preliminary results based on morphological and chronological studies of the Freundlich-Sharonov Basin, one of my study areas on the farside of the Moon that exhibits evidence of mare emplacement.

Development of Readout Electronics for Plastic Scintillators Coupled with a Photomultiplier Tubes (PMTs) for a Hard X-ray Compton Polarimeter

Date: 2025-05-23
Speaker: Mr. Deepak Kumar Painkra
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Photons preferentially undergo Compton scatter perpendicular to the plane of polarization, a property that enables the measurement of linear polarization in hard X-rays. A Compton polarimeter employs a low-Z scatterer to maximize the probability of Compton scattering. This central scatterer is surrounded by a high-Z absorber, which detects the azimuthal distribution of scattered photons. In such a configuration, the lowest photon energy at which polarization can be effectively measured is determined by the lower energy detection efficiency of the scatterer. The efficiency is, in turn, limited by the noise performance of the readout electronics. In this seminar, I will present an overview of the design considerations of the Hard X-ray Compton Polarimeter, with a focus on the development of readout electronics for the scatterer, a plastic scintillator coupled with a PMT. I will also discuss the experiment setup to characterize its detection efficiency at lower energies, aiming to improve the polarimeter sensitivity.

Neutrinoless double beta decay in an realistic SU(5) Model

Date: 2025-05-20
Speaker: Debashis Pachhar, PRL
Venue: Room no: 469 (Main Campus)

Abstract

Baryon number (B) and lepton number (L) are accidental global symmetries of the Standard Model (SM). Any observed violation of these quantum numbers would provide unambiguous evidence for physics beyond the SM. Grand Unified Theories (GUTs) offer a well-motivated framework to study such violations. In this seminar, I will discuss the role of heavy scalar fields in mediating lepton number violation via neutrinoless double beta decay (0νββ) within the SU(5) framework. While the minimal SU(5) setup predicts extremely suppressed contributions to 0νββ due to the heavy scalar masses – as a consequence of the proton decay bound, we will show that this limitation can be circumvented by extending the model. Specifically, the introduction of a discrete ℤ3 symmetry and the inclusion of an additional 15-dimensional scalar representation allow for dominant contributions to the decay process. Such an extension not only remains consistent in yielding realistic fermion mass spectra but also leads to experimentally testable predictions in upcoming ton-scale 0νββ searches.

The Secret Lives of Galaxies: From Dusty Starbursts to Buried Black Holes

Date: 2025-05-20
Speaker: Dipanjan Mitra
Venue: Online:https://imeet.vconsol.com/join/9277507210?be_auth=NDc5OTIx

Abstract

Abstract - Galaxies are the building blocks of the Universe, and some of the most massive and mysterious ones formed when the Universe was just a few billion years old. Many of these early galaxies were rich in dust and forming stars at high rates, yet hidden from view in visible light. These dusty star-forming galaxies (DSFGs) played a key role in building today’s giant elliptical galaxies, and understanding them is essential to piecing together the story of galaxy formation. In my recent work, I used data from space and ground-based telescopes (JWST, Euclid, Herschel, and LSST) to show how we can trace the stars, dust, and AGN activity in these galaxies across cosmic time, and developed physical models. In this talk, I shall demonstrated that by combining multi-wavelength data (from ultraviolet to far-infrared) we can get a complete picture of how galaxies evolve, even when they are deeply buried in dust. I shall also discuss the role deep radio surveys in unveiling obscured active galactic nuclei (AGN) at high redshifts.

Dynamics of Dissolved Organic Matter in Regulated River Systems

Date: 2025-05-20
Speaker: Ms. Ganika Kushwah
Venue: Ground Floor Lecture hall

Abstract

The dynamics of dissolved organic matter has always been complex because of their largely unexplored nature. Freshwater systems such as rivers are vital components of the global biogeochemical system as they act as conduits for transporting large quantities of dissolved organic matter (DOM) from terrestrial landscapes to the ocean. However, their role in DOM dynamics still remains underexplored, specifically from a biogeochemical perspective. Moreover, the anthropogenic alteration to it’s flow regime has put a limit to its transport mechanism-reducing its export. In ths seminar, a basic review of a DOM in riverine system along with results obtained from regulated river systems in western India will be presented

Investigation of Organic Matter in Differentiated Meteorites: Unveiling Indigenous Origins and Impact Dynamics

Date: 2025-05-16
Speaker: Ms. Neha
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The nature of organic matter in meteorites provides insights into early solar system chemistry and the evolutionary histories of their parent bodies, reflecting processes from nucleosynthesis and dust formation to planetesimal and planetary development over the last 4.5 billion years. This talk provides an overview of the first detailed investigation into the nature and origin of insoluble organic matter (IOM) in aubrites, a rare class of differentiated meteorites. I will present a multitechnique analysis of IOM in aubrites and enstatite chondrites, aimed at understanding the extent of organic distribution within the protoplanetary disk and the physicochemical processes that offer essential clues to their parent body evolution. In this seminar, I will discuss the spectroscopic analyses of the IOM in aubrites compared with chondrite IOM to understand the structural and molecular heterogeneity in different meteorite classes. Further I will be discussing the microscopic studies of these organics highlighting the different carbon morphologies present in aubrites. The results offer new insights into the complex evolutionary history of aubrite parent bodies and contribute to a broader understanding of organic matter preservation in differentiated planetary materials.

Can CO2 outgassing explain the Lomagundi carbon isotope excursion?

Date: 2025-05-15
Speaker: Mr. Janaarthanan P A
Venue: Ground Floor Lecture hall

Abstract

The Lomagundi-Jatuli excursion event (2.3-2.0 Ga) is one of grandest carbonate isotopic excursion events in the geological history, that is said to mark a global perturbation in carbon cycle. The canonical explanation given for this excursion attributes it to be the resultant of enhanced organic carbon burial. But, the lack of geological evidence for an enhanced organic matter accumulation prior to or synchronous with the excursion, leaves this event an unanswered puzzle. Furthermore, recent insights from sedimentological facies-based studies challenges the presumed global extent of this excursion. In this discussion we will evaluate the canonical organic burial mechanism and explore the possibility of CO2 outgassing as a potential driver responsible for this excursion.

N-Body Integration Model for Dust Dynamics and Flux Estimation in Inner Solar System

Date: 2025-05-14
Speaker: Ms. Aanchal Sahu
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Interplanetary Dust Particles (IDPs), originating from the Asteroid Belt, Kuiper Belt, Oort Cloud, and comets, are fundamental to many Solar System phenomena such as Zodiacal Light and meteor showers. As these particles spiral inward toward the Sun, their orbits are altered by a complex interplay of gravitational and non-gravitational forces, leading to gradual perturbations in their orbital elements. The mathematical formulation of the force models, orbital perturbation equations, and their impact on dust evolution will be discussed. We utilize and analyse the N-body problem using Everhart’s RA15 version of the RADAU integrator, which is particularly well-suited for handling stiff orbital equations. I will be presenting results highlighting how Mean Motion Resonances (MMRs) facilitate the capture and long-term trapping of dust particles near planets which can alter dust trajectories. Additionally, methodologies for statistical estimation of dust flux on planetary surfaces by analysing the position of dust particles over time during their close encounters with planets will be discussed. The velocity distribution of impacting particles will also be examined to provide a more complete picture of dust-planet interactions.

Electron-phonon coupling induced topological phase transitions in an α-T3 quantum spin Hall insulator

Date: 2025-05-13
Speaker: Dr. Kuntal Bhattacharyya, IIT Guwahati
Venue: Room no: 469 (Main Campus)

Abstract

We study the phenomenon of topological phase transitions induced by electron-phonon (e-ph) coupling in an α-T3 quantum spin Hall insulator that presents smooth tunability between graphene (α = 0) and dice (α = 1) lattice. Upon deriving an effective electronic model under suitable transformations, we come across different regimes of α, which host distinct topological transitions solely mediated through e-ph coupling, manifesting robust support from the bulk gap closing and the relative changes in the topological invariant together with the edge state features. The critical e-ph strengths of these transitions strongly depend on α. We also observe the evidence of an emergent second-order topological insulator (SOTI) phase in our system, which is characterized by the existence of corner modes and its topological marker. Interestingly, these corner modes are wiped out beyond a critical e-ph coupling (albeit different for different α), referring to a SOTI-trivial phase transition induced by the e-ph coupling.

Fate of Environmental Microplastics

Date: 2025-05-13
Speaker: Prof. Neeraj Rastogi
Venue: Ground Floor Lecture hall

Abstract

Microplastics (MPs) are omnipresent on the Earth, found everywhere from Mount Everest to the Mariana Trench, and from fishes to human body. MPs are known to affect human and environmental health directly/indirectly. However, research on MPs is in initial stage only with major focus on 'MPs in water bodies'. This talk will provide a brief overview on the MP research done in different environmental systems and future perspectives.

Understanding evolution of cometary volatiles

Date: 2025-05-09
Speaker: Mr Akshat Rawat
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Understanding the evolution of volatiles on the surfaces and subsurfaces of comets is crucial to studying their thermal, chemical, and structural history. This talk will provide an overview of the key physical processes driving volatile sublimation on comets, including heat conduction, sublimation, and gas diffusion through porous subsurface material. I will then discuss previous models of cometary nuclei and comae, highlighting their limitations—such as neglecting long-term thermal evolution, relying on simplified geometries (spherical or quasi-3D), underutilizing recent spacecraft data, and lacking integration between nucleus and coma evolution. Addressing these gaps, my research focuses on developing a model that comprehensively links the cometary surface and subsurface with the cometary atmosphere to study volatile evolution. This includes implementing coupled thermophysical and sublimation modelling across realistic comet geometries to interpret cometary activity better and simulate volatile loss over time—particularly at larger heliocentric distances (>3 AU), where CO and CO₂ dominate over H₂O as primary drivers of activity.

Atmospheric evaporation from exoplanets

Date: 2025-05-07
Speaker: Dr. Gopal Hazra
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The habitability of any planet is decided by a complex evolution of its interior and atmosphere. Recently in many observations, it has been found that close-in exoplanets are going through significant atmospheric evaporation, which could affect the overall evolution of the exoplanet atmosphere. This atmospheric evaporation from exoplanets is very much dependent on the plasma and radiation environment of their parent stars (e.g., stellar radiation, stellar wind, stellar flares, and Coronal Mass Ejections (CMEs). In this talk, I will explain different physical processes (e.g., Jeans escape, hydrodynamic escape) by which an exoplanet can lose its atmosphere. One major process that leads to significant loss of exoplanetary atmosphere is the stellar radiation-driven atmospheric outflow. Once planetary outflow is initiated from the planet by stellar radiation, it further interacts with the stellar wind shaping up the exoplanetary atmosphere (sometimes producing a comet-like structure) and its atmospheric mass-loss rate. Moreover, flares and coronal mass ejections (CMEs) from the star will also have a great impact on planetary evaporation and mass loss. I will present our newly developed 3D radiation magnetohydrodynamics model where we have implemented a self-consistent radiative transfer of incident stellar radiation to simulate planetary outflow and its interaction with the stellar wind, CMEs, and flares. I will show that radiation-driven planetary outflow alone can not explain the observed transit signatures & corresponding mass-loss rate, but the interaction with the stellar wind/coronal mass ejections can explain the observed mass-loss rate and transit for many exoplanets. I will also discuss briefly the effect of stellar and planetary magnetic fields on the atmospheric mass-loss rate and corresponding observational signatures.

Study of Neutrino Oscillation with non unitarity

Date: 2025-05-06
Speaker: Pathan Tamanna, National Institute of Technology Surat
Venue: Room no: 469 (Main Campus)

Abstract

In this talk we will present the neutrino oscillation probabilities in presence of a non unitary mixing matrix . We will show the oscillation probabilities both in vacuum and including matter effects, Using the expressions of probabilities derived, we will show at which energies and baselines the signature of non unitary will be significantly different from standard scenarios.

Corals as geochemical proxy for N:P ratio: Insight from modern corals

Date: 2025-05-06
Speaker: Dr. Abul Quasim
Venue: Ground Floor Lecture hall

Abstract

Globally, phytoplankton typically maintain the Carbon:Nitrogen:Phosphorus (C:N:P) ratios close to the Redfield ratio (~106:16:1), which reflects the balance of nutrients required for their growth. Therefore, these ratios serve as a baseline for assessing nutrient availability or limitation and carbon export efficiency. Understanding the future shifts in oceanic C:N:P ratios is essentially required for predicting the future trends of the biological pumps under the global climate change scenario. Recent studies reveal that the C:N:P ratios in the global ocean vary regionally, and their future projections are highly uncertain. Understanding the past variability in the C:N:P ratios could improve predictions. However, no geochemical proxy for C:N:P ratios at present. In this context, we analyzed C:N:P stoichiometry as well as d13C and d15N in different layers of modern corals (including coral-mounted algal biofilms) and surrounding seawaters and particulate organic matter collected from the Gulf of Kutch. In this talk, I will share insights into C:N:P ratios in the global ocean, and key findings highlight the efficiency of corals in capturing marine nutrient signatures and the biogeochemical processes shaping elemental and isotopic patterns.

Decoding Aqueous Alteration on Mars: Insights from Water/Rock (WR) ratios in Open and Closed Systems

Date: 2025-05-02
Speaker: Mr Aditya Das
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

In this talk, I will discuss how water/rock (WR) ratios under open and closed system conditions shape secondary mineral formation on Mars. For this, I shall be analyzing the secondary minerals on both Martian meteorites and terrestrial analogues (Deccan basalts from the Kutch area), which will help in understanding the geochemical conditions responsible for such alteration processes that will offer fresh insights into past climates and alteration histories on Mars.

Time-Dependent Modeling of Extreme Gamma-Ray Flares of Blazars

Date: 2025-05-01
Speaker: Anton Dmitriev
Venue: Online

Abstract

Blazar flares offer a unique window into the extreme physics of relativistic outflows, including particle acceleration and the origin of multi-wavelength (MWL) emission. A key approach to studying these processes is physical modeling of varying blazar jet emission. Many numerical codes employ a kinetic framework to track particle spectrum evolution under various physical effects. We have developed EMBLEM (Evolutionary Modeling of BLob EMission), a versatile radiative code based on time-dependent particle (re-)acceleration, escape, radiative cooling, and adiabatic expansion. This code allows us to self-consistently connect low state and flaring emission. Based on a leptonic framework, the code incorporates synchrotron self-Compton (SSC) and external Compton (EC) scenarios. We showcase its application to (1) modeling extreme gamma-ray flares in blazars such as Mrk 421 and 3C 279, and (2) searching for internal gamma-ray opacity signatures in high-redshift blazars.

Neutrinos in Cosmology

Date: 2025-05-01
Speaker: Sanjit Kumar, NIT Jamshedpur
Venue: Room no: 469 (Main Campus)

Abstract

In this talk, we will begin by introducing the basics of neutrinos and their significant role in cosmology. We will discuss the thermodynamics of the early universe and examine the Boltzmann equation and the process of neutrino decoupling. Moving forward, we will explore the nature of dark matter and investigate whether neutrinos could serve as viable dark matter candidates. We will then review cosmological constraints on neutrino masses. Finally, we will discuss the possibility of sterile neutrinos as dark matter. Throughout the talk, we aim to highlight how neutrinos influence key processes in the early universe and their relevance in modern cosmology.

Magnetic Accretion Signatures in High-Field Cataclysmic Variables

Date: 2025-04-29
Speaker: Akash Sundriyal
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Cataclysmic Variables (CVs) are examples of semi-detached binary star systems characterized by the flow of stellar material from the companion star to the primary (white dwarf). If the primary possesses a significant magnetic field, the accretion dynamics can be drastically altered. In particular, polar magnetic CVs, characterized by their strong magnetic fields are often marked by the lack of an accretion disk and also exhibit unique observational signatures, such as highly polarized radiation, synchronous rotation, etc. In this talk, I will discuss the properties of these high field systems and the interaction between the magnetic field and the accretion flow which can lead to complex phenomena, including emission of X-rays and cyclotron radiation. I will then explain some methods used to probe the magnetic field in such systems. I will also discuss the identification of potential high field systems from a sample of CV candidates from the 5th data release of the LAMOST (Large Sky Area Multi-Object Fiber Spectroscopic Telescope) spectroscopic survey. I will conclude my talk by presenting an estimate for the magnetic field in LAMOST J003553.36+433341.4 from its LAMOST spectrum.

Investigating the Impact of Hydrogen on Lunar Neutron Leakage Flux

Date: 2025-04-25
Speaker: Ms. Shipra
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The Moon's lack of a magnetic field and atmosphere exposes its surface to ionizing radiation, including the solar wind, solar energetic particles (SEPs), and galactic cosmic rays (GCRs). High-energy GCRs interact with the lunar surface, generating fast neutrons through nuclear reactions. These fast neutrons are moderated by collisions with the nuclei in the lunar soil and can leak out, acting as messengers of the soil’s composition. Studying the neutron leakage spectrum can reveal important information about the abundance of near-surface hydrogen. In this seminar, I will discuss the production and moderation processes of neutrons within the lunar surface, followed by an explanation of how the leakage neutron flux depends on hydrogen and other elements.

Verification of the Dynamically New Comets: Results from the N-body Simulation

Date: 2025-04-24
Speaker: Goldy Ahuja
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Comets are the preserved minor bodies which holds the primitive information about the early solar system. These bodies come into the inner solar system from two reservoirs, i.e., Kuiper Belt and Oort Cloud. Kuiper Belt is the source of Short-Period, low-inclination comets (SPCs) whereas Oort Cloud is the source of Long-Period Comets (LPCs) having isotropic inclination. Dynamically New Comets (DNC) are a long-period comets, with a semi-major axis > 10000 AU, entering the inner Solar System for the first time, which gives us an excellent opportunity to study their composition and origin. In this talk, I will explain the early classification for comets based on the basis of different dynamical and chemical properties. I will then explain the origin of a few long-period comets using the N-body dynamical simulation package, REBOUND. I will explain the N-body simulation code and benchmarking test with the well known asteroid, APOPHIS. I will conclude my talk with the inclusion of Non-gravitational forces and the difference with the results.

Magnitude and regulation of methane emission from tropical streams and rivers

Date: 2025-04-24
Speaker: Dr. Latika Patel
Venue: Online

Abstract

Inland waters, particularly fluvial systems, are significant sources of atmospheric methane (CH4), a greenhouse gas with 34 times the global warming potential of carbon dioxide. However, large uncertainties persist regarding the extent and controls of CH4 emissions, especially in tropical river basins like those in Southeast Asia. Research work during my PhD addressed three critical knowledge gaps in understanding CH4 dynamics in tropical fluvial systems: (1) the effect of land use changes on CH4 concentration and emissions, (2) the occurrence and regulation of oxic CH4 production (OMP), and (3) the extent and environmental controls of aerobic CH4 oxidation (MOX), which will be discussed during the seminar.

Advances in Direct Imaging of Exoplanets

Date: 2025-04-23
Speaker: Dr. Prashant Pathak
Venue: Seminar Room # 113/114 (Thaltej campus)

Abstract

Direct imaging of rocky exoplanets remains a major scientific objective for current and next-generation large telescopes. While existing facilities have successfully imaged young, Jupiter-mass exoplanets at wide separations (>0.1"), detecting smaller, rocky planets poses a significantly greater challenge due to the stringent contrast requirements. The mid-infrared (mid-IR) regime offers a promising solution, providing optimal planet-star contrast for detecting thermal emissions from exoplanets in our solar neighbourhood. In this talk, I will discuss the key techniques enabling direct imaging of exoplanets, with a focus on two mid-IR high-contrast imaging (HCI) instruments: NEAR (New Earths in the Alpha Cen Region) and METIS (Mid-infrared ELT Imager and Spectrograph). The NEAR experiment demonstrates the feasibility of HCI at ten microns, achieving sub-mJy sensitivity within a few hours—sufficient to detect multiple Jupiter-mass planets around nearby stars. I will present its operational principles and scientific outcomes. Furthermore, I will explore METIS, the first-generation instrument for the Extremely Large Telescope (ELT), highlighting its HCI capabilities and expected performance.

Origin of Soft excess in Mrk50

Date: 2025-04-22
Speaker: Narendranath Layek
Venue: Seminar Room # 113/114 (Thaltej campus)

Abstract

Active galactic nuclei (AGNs) are the most luminous and energetic sources in the universe, powered by the accretion of matter onto supermassive black holes (SMBHs) located at the centers of host galaxies. The soft excess refers to an enhancement of flux in the soft X-ray range (belowâˆ¼2 keV) over the primary power-law continuum, commonly observed in most Seyfert 1 AGNs. Its origin is a long-standing and unsolved puzzle in AGN studies. To investigate this, we conducted an extensive temporal and spectral analysis of the Seyfert 1 AGN Mrk 50, utilizing the observations from XMM, Swift, and NuSTAR. Two possible physical scenarios explain the origin of soft excess in AGNs , Warm Comptonization and Reflection from the ionized accretion disk. Both physical models successfully explained this behaviour in Mrk 50. Further, we investigated the origin using a model-independent approach using cross-correlation analysis between two X-ray bands (soft and hard) to examine the correlations and delays between them. In this seminar, I will present a detailed study of the origin of the soft excess in Mrk 50, based on our temporal and spectral analysis.

Static structure factor and the dispersion of the Girvin-MacDonald-Platzman density mode for fractional quantum Hall fluids on the Haldane sphere

Date: 2025-04-22
Speaker: P. Rakesh Kumar Dora, The Institute of Mathematical Sciences, Chennai
Venue: Room no: 469 (Main Campus)

Abstract

We study the neutral excitations in the bulk of the fractional quantum Hall (FQH) fluids generated by acting with the Girvin-MacDonald-Platzman (GMP) density operator on the uniform ground state. Creating these density modulations atop the ground state costs energy since any density fluctuation in the FQH system has a gap stemming from underlying interparticle interactions. We calculate the GMP density-mode dispersion for many bosonic and fermionic FQH states on the Haldane sphere using the ground state static structure factor computed on the same geometry. Previously, this computation was carried out on the plane. Analogous to the GMP algebra of the lowest Landau level (LLL) projected density operators in the plane, we derive the algebra for the LLL-projected density operators on the sphere, which facilitates the computation of the density-mode dispersion. Contrary to previous results on the plane, we find that, in the long-wavelength limit, the GMP mode accurately describes the dynamics of the primary Jain states."

Biogeochemical implications of Ocean Alkalinity Enhancement

Date: 2025-04-22
Speaker: Ms. Shreya Mehta
Venue: Ground Floor Lecture hall

Abstract

Over the past few centuries, anthropogenic activities have significantly altered the global carbon cycle, leading to a ~ 50% increase in atmospheric CO2 concentration relative to the pre-industrial levels. This rise has contributed to a global surface temperature increase of approximately 1.1°C (IPCC, 2023). To limit the future warming, it is being widely acknowledged that in addition to immediate reduction in greenhouse gas emissions, excess CO₂ needs to be actively removed from the atmosphere through carbon dioxide removal (CDR) methods. One promising CDR approach is Ocean Alkalinity Enhancement (OAE), which involves the addition of alkaline mineral to the ocean to enhance the oceanic uptake of atmospheric CO2 and is subsequently stored as dissolved inorganic carbon (DIC) over long periods. In addition to CO2 removal, OAE may also help mitigate ocean acidification by increasing the pH of water. Despite its potential, significant uncertainties remain regarding the feasibility, effectiveness, and environmental implications of implementing OAE at a global scale. To address these knowledge gaps, we conducted mesocosm experiments in the coastal waters of the Arabian Sea. These experiments aimed to investigate the effects of OAE on the carbon (C) and nitrogen (N) biogeochemical cycles within the marine ecosystem. In this seminar I will present some preliminary findings on how OAE influences carbon and nitrogen uptake rates in the coastal regions of the Arabian Sea.

Investigating the explosion and progenitor properties of Type II core-collapse supernovae

Date: 2025-04-17
Speaker: Dr. Bhavya Ailawadhi
Venue: Online:https://imeet.vconsol.com/join/9563852195?be_auth=NDU5MzEx

Abstract

This presentation highlights the core components of my doctoral research, which focused on the photometric and spectroscopic characterisation of Type II core-collapse supernovae (CCSNe) and the development of automated data processing tools for time-domain surveys. CCSNe are end stages of massive stars, contributing to the chemical enrichment of the interstellar medium and influencing galaxy evolution through the dispersal of heavy elements. I conducted detailed observational studies of two transitional SNe—2020aze and 2020jfo—which do not fit cleanly into the classical Type IIP or Type IIL categories. SN 2020jfo exhibited a shorter plateau duration but shared key properties with Type IIP SNe. At the same time, SN 2020aze displayed characteristics that were more aligned with Type IIL SNe, including early flash features and a faster decline during the photospheric phase. These analyses contribute to the growing understanding that Type IIP and IIL SNe form a continuum rather than distinct classes. To investigate the role of progenitor environments, I conducted a statistical study on a broader sample of SNe by estimating metallicities using Fe line equivalent widths. This analysis provided insights into how progenitor metallicity influences light curve morphology and explosion characteristics. Complementing the observational work, I developed a fully automated aperture photometric pipeline in Python for the 4.0m International Liquid Mirror Telescope (ILMT). The pipeline processes time-delay integration (TDI) mode data, performs astrometric calibration, computes instrumental magnitudes, and derives calibrated light curves using catalogues like Pan-STARRS and SDSS. The pipeline is fully functional and is being used to derive long term light curves of variable sources.

Global Detection of Lunar Pyroclastic Deposits (LPDs)

Date: 2025-04-11
Speaker: Mr Dibyendu Misra
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Lunar Pyroclastic Deposits (LPDs) are fine-grained, low-albedo, Fe-Ti-rich volcanic glass-dominated lithological units typically associated with thin crust and extensional tectonic regimes on the Moon. These deposits are providing key insight into thermal evolution and volatile inventory of the Moon. However, their remote detection remains challenging due to the spectral similarities between volcanic glasses and Fe-bearing common lunar minerals (e.g., Olivine, Pyroxene, etc.) in the visible to near-infrared (VIS-NIR) spectral range. In this seminar, I will present a novel approach developed for remote detection of LPDs by incorporating morphological understanding with the spectral analysis covering both the spectral parameters. I will present new global LPDs maps, based on the Moon Mineralogy Mapper (M3) data of two different optical periods. The results will be validated by comparing the global outcomes to already reported LPDs. The main outcome of this work is new detections. I will present a few case studies on new detections and validation to confirm their pyroclastic origin. I will also discuss the inferences and implications during this seminar.

Higher-Order QCD Corrections and Threshold Resummation for Processes in the Standard Model and Beyond at Hadron Colliders

Date: 2025-04-11
Speaker: Chinmoy Dey, IIT Guwahati
Venue: Online--- https://imeet.vconsol.com/join/9927407570?be_auth=NjU4MDkx

Abstract

In this talk, we present our study on threshold resummation for various Standard Model processes at the Large Hadron Collider (LHC), including neutral and charged Drell-Yan production, Higgs boson production in association with a massive vector boson, and Higgs production via bottom quark annihilation. We perform resummation up to N³LO+N³LL accuracy in QCD, addressing the large logarithms that arise in the partonic threshold limit. Additionally, we analyzed the gluon fusion channel for ZH production, resumming contributions up to NLO+NLL accuracy in the Born-improved theory and combining them with Drell-Yan-type contributions. For on-shell ZZ pair production, we extend the resummation accuracy to NNLO+NNLL. After performing the threshold resummation, the theoretical uncertainties are reduced compared to fixed-order results. Furthermore, we investigate the two-loop corrections to the decay of a pseudo-scalar Higgs boson (A) into three partons, including higher-order terms in the dimensional regulator. These results are crucial for improving theoretical predictions for pseudo-scalar production with one jet at hadron colliders.

Delving into the Extremes of Neutron Stars: Insights from Thermonuclear X-ray Bursts

Date: 2025-04-08
Speaker: Dr. Gaurava Kumar Jaiswal
Venue: Online:https://imeet.vconsol.com/join/2150369168?be_auth=NTI3ODEz

Abstract

Neutron stars (NSs) are ultra-dense remnants of massive stars, characterized by immense gravitational fields, temperatures, and densities, making them unique laboratories for studying matter under extreme conditions. Type-I X-ray bursts, observed from accreting NSs in low-mass X-ray binary systems, provide valuable insights into these environments. These bursts are driven by unstable thermonuclear burning of accreted hydrogen and/or helium on the NS surface, typically lasting from tens to hundreds of seconds, depending on the fuel composition. About 20% of these bursts are energetic enough to temporarily lift the NS photosphere by tens to hundreds of kilometers. Additionally, the nuclear burning during the bursts leads to the synthesis of elements as heavy as those in the Sn-Sb-Te mass region. Studying these events offers critical information about nuclear processes, burst-accretion disk interactions, and provides important constraints on NS properties such as spin and compactness. Observations from the Neutron Star Interior Composition Explorer (NICER) have advanced our understanding by offering unprecedented timing and good spectral sensitivity, enabling detailed studies of X-ray bursters. This talk will focus on the latest NICER findings, highlighting the complex interplay between X-ray bursts, accretion dynamics, and nucleosynthesis, and how these observations can help constrain the equation of state of NSs - the "holy grail" of NS physics.

Anatomy of Monsoon Break Spells: A Probabilistic Approach

Date: 2025-04-08
Speaker: Mr. Akash Ganguly
Venue: Ground Floor Lecture hall

Abstract

The Indian Summer Monsoon (ISM) is vital to India’s economy, and is intrinsically linked to the dreams and aspirations of over a billion people residing in the Indian subcontinent. Several causal mechanisms operating at differing spatio-temporal scales dictate the ISM performance, driving large inter-annual variability. Since the turn of the century, there has also been a conspicuous rise in both the frequency as well as intensity of extreme events, marking a discernible shift from the climatological trends. Such events have significant consequences necessitating the need for improved understanding of the causal mechanisms, as well as improved forecast skill for efficient water resources management. One such type of climatic extremes: the ‘monsoonal breaks’ are marked by a pause in the ISM synoptic system, resulting in reduced overall rainfall, and are accompanied by suppressed convection over the Monsoon Core Zone (MCZ), extended dry periods, heatwaves, and severe droughts as a direct consequence. However, the spatio-temporal pattern of rainfall distribution over the MCZ exhibit significant variability. Due to this inherent unpredictability and randomness, analyses often focus on aggregated rainfall data to discern broader trends and patterns. In this study, we demonstrate that the seemingly random pattern of rainfall, when analysed at small (1̊X1̊) spatial scales is indeed information rich, which can be efficiently churned out with the help of simple statistical tools. We find that the divergence of the rainfall distribution from the climatological trend exhibits symmetries. This information, which is otherwise averaged out can be leveraged to gain novel insights into the underlying causal mechanisms, thereby contributing to improved skill of forecasting extended monsoonal breaks. We extend the analysis to map the rainfall anomalies to the corresponding anomalies in the mean wind field, thereby identifying the dominant pathways of anomaly propagation and further extending the possible scope of forecasting such precipitation extremes.

The Role of Layered Minerals in the Origin of Life Insights from Planetary Analogue Terrestrial Geomaterials

Date: 2025-04-07
Speaker: Dr Amritpal Singh Chaddha
Venue: online

Abstract

How did life begin? Researchers believe that certain minerals, especially clays, played a big role in this process. These minerals can hold onto organic molecules, help chemical reactions happen, and create safe spaces for early life to form. Since they exist on Earth and other planets, they also help us search for signs of life beyond our planet. These layered minerals, abundant in terrestrial and extraterrestrial environments, serve as key indicators of fluid-rock interactions and potential biosignature preservation. This talk will explore how clays can serve as one of the potential planetary analogue terrestrial geomaterials that can enhance our understanding of life’s emergence. By employing comprehensive biogeochemical fingerprinting, this research will characterize clay minerals in terrestrial settings, assessing their capacity to preserve biosignatures. By studying layered minerals on Earth and extending these findings to available extraterrestrial samples, we can unveil the largely unexplored role of clay minerals in the origin of life, which is essential for planning future astrobiological missions.

Towards a Unified Understanding of Accreting Compact Objects

Date: 2025-04-07
Speaker: Dr. Aru Beri
Venue: Online:https://imeet.vconsol.com/join/8175021695?be_auth=MzAwMTg1

Abstract

Accreting neutron stars and black holes in X-ray binaries are powerful laboratories for exploring extreme physical conditions such as strong gravity, dense matter, and intense magnetic fields. In this talk, I will present recent discoveries from fast X-ray timing and spectral observations, including coherent and incoherent variability that reveals the nature of the innermost regions of these systems. Drawing on results from the AstroSat survey, I will highlight the discovery of an intermittent accretion-powered millisecond X-ray pulsar (AMXP)—a transient source and potential gravitational wave emitter. I will also explore the role of transient events, such as outbursts, in advancing our understanding of accretion processes and how multi-wavelength campaigns help capture the dynamic behavior of both neutron star and black hole systems. Finally, I will discuss the potential of combining X-ray polarization with timing-spectral and multi-band observations to build a more complete picture of both persistent and transient accreting compact objects.

A Monte Carlo Approach to Temperature and Spectral Energy Distribution in Protoplanetary Disks

Date: 2025-04-04
Speaker: Mr Soumik Kar
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

A protoplanetary disk is a rotating circumstellar disk of dense gas and dust surrounding a young star. Understanding the structure and composition of these disks is essential for understanding the processes involved in planet formation. Over the years, various models have been developed to describe the chemical and hydrodynamic processes occurring within these disks. Here, we introduce a Monte Carlo Radiative Transfer (MCRT) model to characterize the temperature distribution and spectral energy throughout the disk and its surrounding envelope. MCRT method provides an efficient means of achieving radiative equilibrium without iteration in systems with temperature-independent opacity sources. Additionally, the computational time required for this method is comparable to that of pure scattering models. The MCRT approach tracks individual photon packets, allowing for precise identification of energy absorption sites and subsequent adjustments to local cell temperatures. To enforce radiative equilibrium, each absorbed packet is instantly re-emitted, with its frequency selected to correct the cell’s thermal spectrum. These re-emitted packets can undergo scattering, absorption, and re-emission processes until they escape, enabling the system’s temperature and spectral energy distribution (SED) to reach equilibrium. We present the initial results of the simulations for both spherical symmetry models and 2D axisymmetric density structures, comparing the findings with standard benchmark tests.

FIELD-ANGLE OPTIMIZED DESIGN FOR WIDE-FIELD IMAGING X-RAY TELESCOPES

Date: 2025-04-03
Speaker: Mr. Neeraj K. Tiwari
Venue: Seminar Room # 113/114 (Thaltej campus)

Abstract

Wide field of view (FOV) imaging X-ray telescopes play a crucial role in addressing some of the most challenging and unresolved questions in modern astrophysics. For example, they are crucial for probing the early formation of supermassive black holes (SMBH), rigorously testing the hypothesis that nanoflares are the primary mechanism sustaining coronal temperatures above million Kelvin, and detecting the electromagnetic counterparts of gravitational wave events. However, existing optical designs for X-ray telescopes, such as the Wolter type-1 (W1) and Wolter-Schwarzschild (WS) configurations, offer high angular resolution only along the optical axis and are therefore limited to narrow FOVs (a few arcminutes), while the scientific cases mentioned above require high angular resolution across a much wider FOV (up to 60 arcminutes). In this talk, I will introduce a new optical design, the field-angle optimized (FO) design, specifically developed for wide FOV X-ray imaging telescopes. I will discuss the methodology behind this design, compare its performance with existing optical designs, and explore its feasibility for implementation in wide FOV solar X-ray telescopes.

Time domain photometric study of peculiar Blazars

Date: 2025-04-01
Speaker: Dr. Shubham Kishore
Venue: Online: https://meet.google.com/ihi-bmxq-syc

Abstract

Blazars often exhibit random, aperiodic, and stochastic behaviours in their flux across all observational electromagnetic (EM) bands over a wide range of timescales. However, the underlying causes are not yet fully understood regarding which flux variations on the intra-day/day timescales are most poorly comprehended. These variations are primarily related to accretion or jet physics, as jets are powered by accretion. In the talk, I will elucidate my findings that include the quasi-periodic oscillatory signatures and flare episodes detected in three individual Blazar candidates observed with Transiting Exoplanet Survey Satellite (TESS).

Habitat Selection by Early Humans in the Indian Subcontinent

Date: 2025-04-01
Speaker: Ms. Nandini Sharma
Venue: Ground Floor Lecture Hall

Abstract

The dispersal of our species out of Africa is believed to have occurred in multiple phases from the middle to late Pleistocene. Earliest fossil evidences for this migration of Homo sapiens is documented around 200-100 kya. These dispersals are influenced by the climate shifts, which shaped their habitats during migration. According to the Southern Dispersal Hypothesis, the dispersal of Homo sapiens from Africa into South Asia (130–75 kya) coincided with periods of favorable monsoon-driven green corridors, which influenced migration pathways and habitat selection. In this seminar, we will explore hominin habitat selection patterns by reconstructing woody cover along these dispersal routes using pedogenic carbonates as a vegetation proxy, providing insights into the environments they might have encountered and adapted.

Identification of Whistler Waves Near Flux Ropes in the Nightside Magnetosphere of Venus

Date: 2025-03-28
Speaker: Ms. Aarti Yadav
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Whistler waves are electromagnetic plasma waves which are generated by temperature anisotropy instability in magnetized plasma. These right-handed circularly polarized waves propagate along the ambient magnetic field in a magnetized plasma. Atmospheric lightning has been considered a natural source of whistler waves at Venus. Recent observations from the Parker Solar Probe (PSP) during its fourth Venus Gravity Assist (VGA) detected whistler wave bursts in the Venusian magnetotail, with further analysis indicating a non-planetary origin. Magnetic reconnection, a fundamental plasma process which may be responsible for atmospheric erosion and dynamic magnetic activity in Venus' induced magnetosphere, emerges as a potential candidate. Observations at Earth have detected whistler waves near magnetic reconnection regions. Venus Express observed magnetic flux rope structures, which are formed by reconnection in Venus' magnetotail. This study explores the detection of whistler waves in the vicinity of these flux rope structures, bridging the concept of whistler wave generation via magnetic reconnection at Venus.

Banded Iron Formations: Archives of Precambrian ocean-atmospheric redox conditions

Date: 2025-03-25
Speaker: Dr. Ajay Dev Asokan
Venue: Ground Floor Lecture Hall

Abstract

Banded Iron Formations (BIFs) are chemical sedimentary rocks with alternating silica and iron-rich bands. The composition of well-preserved BIFs records the seawater composition from which they precipitated and hence, can be used to infer the evolution of Precambrian ocean, ocean-atmospheric redox conditions as well as the emergence of continental crust. Based on associated litho units, BIFs are classified mainly into two variants, i.e., Algoma-type BIFs, that are associated with volcano-sedimentary sequences and Superior-type BIFs, that are associated with clastic sediments. In this presentation, I’ll discuss about different views on BIFs, including the origin of their banding, primary mineralogy and post-depositional alteration, with a focus on trace element compositions of Superior-type BIF from the Bastar Craton and Algoma-type BIF from the Dharwar Craton. The BIFs from the Bastar Craton records Archean seawater compositions, while those from the Dharwar have been significantly modified by post-depositional alteration.

Hidden’ magnetism and a mechanism for it

Date: 2025-03-25
Speaker: Dr. Aabhaas Vineet Malik, Birla Institute of Technology and Science Pilani, KK Birla Goa campus
Venue: Room no: 469 (Main Campus)

Abstract

Recently a mysterious hidden magnetic memory, which manifests itself in the form of “spontaneous” vortices appearing in the superconducting state of 4Hb-TaS2, was reported [Nature, 607,692, 2022]. Motivated by this observation, we present a mechanism which leads to a similar phenomenology. The mechanism relies on spin-charge separation induced by strong electronic correlations in a flat-band tuned away from half filling, which is the expected picture of the T-layers in 4Hb-TaS2. For concreteness, we demonstrate the feasibility of this mechanism within a square lattice t-J model. Our results pave the way towards understanding the observed magnetic memory effect and may apply to a broader class of materials.

Towards Quantum Simulating QCD

Date: 2025-03-25
Speaker: Dr. Indrakshi Raychowdhury, Birla Institute of Technology and Science Pilani, KK Birla Goa campus
Venue: Room no: 469 (Main Campus)

Abstract

Being created from the Big Bang - evolved to families of sub-atomic particles - landing in an astrophysical environment -the dynamic properties of the strong interactions of nature are still unknown. Simulating the dynamics of quantum chromodynamics (QCD) is beyond the scope of even the most powerful supercomputers. Standing at the end of the first quarter of the century, the question is whether a quantum computer can (/will be able to) simulate nature. Okay, yes, it should. The visionary physicist Richard P. Feynman envisioned that "Nature isn't classical, dammit, and if you want to make a simulation of nature, you'd better make it quantum mechanical..." After almost half a century as quantum technology matures it appears to be close to a reality. Yet, as Feynman envisioned, the task remains challenging and requires substantial advancement in `qubitizing/quditizing’ nature - develop novel quantum algorithms and implement them on quantum hardware. In this talk, I'll briefly summarize the journey towards quantum simulating QCD - the challenges, advances and prospects.

Electrostatic Dust Detachment

Date: 2025-03-21
Speaker: Mr Trinesh Sana
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The electrostatic processes are fundamentally important in understanding particle dynamics and the complex dusty plasma environment over the Moon. While many studies have examined dust levitation, the detachment of dust from the lunar surface remains a key factor in understanding the lunar dusty plasma environment. Dust particles on the charged lunar surface experience gravity, cohesion, and electrostatic forces. Typically, the electrostatic force derived from a uniformly charged surface (from Gauss Law) is insufficient to lift the particles against gravity. In this presentation, I will demonstrate that sufficient electric field and coulomb repulsion can be created between the dust and surface due to charge fluctuations on a microscopic scale, which can detach the dust particle from the lunar surface, overcoming dust-surface adhesive force.

From Monopole-Induced Berry Phase to Quadrupolar Berry Phase

Date: 2025-03-21
Speaker: Prof. Sourin Das, Indian Institute of Science Education and Research, Kolkata
Venue: Room no: 469 (Main Campus)

Abstract

We explore the Berry phase associated with purely quadrupolar states (⟨ψ|S|ψ⟩ = 0) in spin-1 systems. By employing the Majorana stellar representation, we demonstrate the topological nature of the quadrupolar Berry phase, revealing that it takes values of either 0 or π, and establish its connection to the exchange of Majorana stars. Additionally, we investigate the dynamics of a state within the quadrupolar subspace under the influence of a static magnetic field. The time evolution governed by this Hamiltonian confines the system to the quadrupolar subspace, generating a geometric phase of the Aharonov-Anandan type, quantized to 0 or π. We also present a natural framework for understanding the topological properties of this subspace in terms of anti-unitary symmetries. Finally we will discuss a possible application of our findings to Holographic quantum codes and robust quantum phase gates.

The African Network of Women in Astronomy (AfNWA) and SciGirls: Examples of social activism

Date: 2025-03-20
Speaker: Dr. Mirjana Povic
Venue: Online: https://meet.google.com/cuw-pwht-zej

Abstract

The world faces a significant gender gap in science. In Africa, in average the population of female scientists is below 25%. The African Network of Women in Astronomy (AfNWA) is an initiative that aims to connect women (or people who identify as such) working in astronomy and related fields in Africa. It was established in September 2020 as one of the committees of the African Astronomical Society (AfAS). With AfNWA we want to ensure the future participation of girls and women at all levels in the development of astronomy and science in Africa. Our main goals are to improve the status of women in science in Africa and to use astronomy to empower girls and women, and to inspire more girls to pursue Science, Technology, Engineering and Mathematics (STEM). This talk will summarise the activities carried out by AfNWA and the current status of women in astronomy in Africa. It aims to give visibility to the work and achievements of the AfNWA community, and the various activities carried out across the continent to support girls and women living and working in under-represented communities through astronomy. In Ethiopia, only about 13% of all scientists are women, and this fraction is even lower when considering the fundamental sciences. Girls avoid choosing STEM mainly due to a lack of support and/or information. This becomes even more evident when going to remote areas, where 80% of the Ethiopian population lives. The SciGirls project aims to improve the gender gap in science in the long-term by empowering female secondary school students and their female science teachers who are working and living in remote and rural areas through astronomy and its multidisciplinarity. In 2022 and 2024 we organised a carefully designed capacity-building workshop for 60 participants across Ethiopia, with the aim of training future STEM advocates in rural and remote areas. The girls and teachers carried out different activities in their communities after the training. Most of participants came from the regions that have been severely affected by conflicts over the past 4 years. SciGirls is one of the 2022 and 2024 projects funded by OAD. During this talk, we will share valuable experiences we have gained through interaction with girls and female teachers who work and live in very harsh conditions, where they rarely have any external support to fulfill their dreams. The SciGirls approach has so far yielded very positive results and the project can serve as a model also in other countries.

Gamma-Ray Bursts (GRBs) as electromagnetic (EM) counterparts of Gravitational Wave (GW) sources

Date: 2025-03-06
Speaker: Dr. Suman Bala
Venue: Room No. 113, Thaltej

Abstract

Gamma-Ray Bursts (GRBs) are the brightest explosions in the Universe since the Big Bang. We have comprehensive knowledge about the GRBs, but there are many open questions even after fifty years of the first detected GRB, especially about the prompt emission phase. The detection of gamma-ray burst GRB 170817A by Fermi-GBM, coinciding with gravitational wave (GW) GW170817, is one of the extraordinary discoveries in the history of the multimessenger era. It is not only the first binary neutron star (BNS) merger detected by the advanced (LIGO-Virgo) GW detectors; it is the only GW detection with a confirmed electromagnetic (EM) counterpart. The Fermi Gamma-ray Burst Monitor (GBM) is an all sky monitoring instrument sensitive to photon energies from 8 keV to 40 MeV. Its capabilities makes it ideal for providing simultaneous gamma-ray observations of gravitational-wave transients. Fermi-GBM continues to look for similar multimessenger detections through on-board triggers as well as subthreshold searches for weak transients, performed both in high-time-resolution continuous data and in targeted follow-ups of gravitational-wave events. In this talk, I will present an overview of GRBs and recent results from targeted and subthreshold searches as a counterpart of GW events.

Hot Jupiter Exoplanets: The Enigmatic Giants of Astrophysics

Date: 2025-03-04
Speaker: Dr. Soumya Sengupta
Venue: Room No. 113, Thaltej

Abstract

Since the discovery of the first exoplanet, 51 Pegasi b, Hot Jupiters (HJs)—Jupiter-like exoplanets orbiting close to their host stars—have remained a central focus in exoplanetary science. Unlike planets in our solar system, these unique systems allow us to study them directly through their infrared emission. Due to intense stellar irradiation, Hot Jupiters exhibit extremely high temperatures, resulting in distinct emission spectra originating primarily from their day-side hemispheres, especially in tidally locked systems. Analyzing these emission spectra provides valuable insights into the temperature structure and chemical composition of these intriguing exoplanets. However, the overlap between planetary and stellar emissions poses a persistent challenge for planetary atmospheric modeling. Additionally, the strong day-night atmospheric flow, driven by the extreme temperature contrast between hemispheres, introduces variability in the observed emission spectra. Another intriguing feature of Hot Jupiters is their larger observed radii compared to Jupiter; a phenomenon known as the radius inflation problem. In this talk, I will explore these fascinating questions surrounding Hot Jupiters, using fundamental physics concepts to unravel the mysteries of these extraordinary worlds.

Echoes of the Ancient Earth: A Quarter Century of Exploring the Vindhyan Basin’s Secrets

Date: 2025-03-04
Speaker: Dr. Jyotiranjan S. Ray
Venue: Ground Floor Lecture Hall

Abstract

The first known animal life on Earth dates back to 630 million years. However, in 1998, a couple of fossil discoveries shook the geoscience world with their spectacular claims of the presence of advanced animal life in rocks of the Vindhya mountains that were generally considered to be older than 1100 million years. These findings sparked intense controversies about their legitimacy and the host rocks' ages. We took up the challenge of dating these rocks deposited in India's largest Proterozoic sedimentary basin. In the last 25 years, we have not only been able to resolve the chronology of the Vindhyan Supergroup, but also made many significant contributions to the study of regional stratigraphy and environment, ocean chemistry and tectonics during the Proterozoic. In the talk, I shall share some of our important findings.

Unravelling Mar’s Magmatic Past: Insights from Martian Shergottites

Date: 2025-02-28
Speaker: Ms Varsha M Nair
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Shergottites, constituting around 90% of the Martian meteorite collection, are categorized into various types: basaltic, olivine-phyric, poikilitic, and gabbroic. Notably, poikilitic shergottites are distinct from the other shergottites as they are cumulate and form at the deep interior into the Mars in comparison to the other extrusive members. This study delves into the mineralogy and petrology of a poikilitic shergottite, NWA 1950 to constrain Martian igneous processes and identify mantle source reservoirs for shergottites. Additionally, the olivine-hosted melt inclusions help to constrain parental melt compositions, mantle sources, and formation processes, while also reconstructing magma evolution from emplacement to ascent.

Health risks of air pollution in a warming climate: Current evidence and New directions

Date: 2025-02-26
Speaker: Dr. Sagnik Dey
Venue: Ground Fllor Lecture Hall

Abstract

Air pollution has been identified as the leading environmental health risk globally. In India, air pollution has been identified as the second largest health risk after maternal and child malnutrition. Health risks attributable to air pollution require robust exposure estimates, sociodemographic conditions and background disease rates. The Global Burden of Disease (GBD) Study has provided a robust framework to estimate the health burden of air pollution. However, the current estimates, available at state levels, have two critical assumptions. First, the risk is considered to be uniform across the composition, neglecting the issue of particle toxicity. Second, the exposure-response functions are derived from cohorts primarily conducted in developed countries. Lack of robust exposure data hindered the generation of India-specific exposure-response functions for non-communicable diseases. In this talk, I will demonstrate the recent advancements in exposure modelling and how such data is being used for health studies, addressing these two aspects. I will also highlight the complex pathways between air pollution and climate and how the air pollution attributable burden is expected to change in future. My talk will demonstrate the urgent need for a collaborative and systematic approach to understand and minimise environmental health risks in India.

Identification and Characterization of Topside V3 Layer of Venusian Ionosphere

Date: 2025-02-14
Speaker: Satyandra Mohan Sharma
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The dayside Venusian ionosphere is produced by photoionization (primary) and photoelectron impact (secondary) ionization from solar EUV (10-105 nm) and SXR (0.1-10 nm) radiations producing V2 (~140 km) and V1 (~125 km) layers. Previous observations from missions such as the Mariner, Venera, and Pioneer Venus Orbiter also reported a "bulge" at 160–200 km altitudes. This bulge has not been documented in any of the standard ionospheric model. Moreover, there have been a limited data of the ionospheric observation during low solar activity which further constrain the characterization of this V3 layer. Using electron density profiles observed by VeRa radio occultation experiment under varying solar activity levels and solar zenith angles (SZAs), we examined the bulge, known as the "V3 layer". Our study analyzed over 200 electron density profiles to characterize this V3 layer. In this seminar I will briefly summarize the results of V3 layer morphology and occurrence rate under varying Solar activity and SZA conditions.

Fabry-Perot wavelength calibration system for precise radial velocity measurements

Date: 2025-02-13
Speaker: Shubhendra Nath Das
Venue: Seminar Room # 113/114 (Thaltej campus)

Abstract

Although more than 5000 exoplanets have been detected, only a few have had their profiles constructed. Besides the radius, mass is significant variable as well, which makes the radial velocity (RV) method important. Yet, instruments and calibration of the equipment pose constraints when it comes to the detection of small Doppler shifts (sub-m/s). One such issue is the accuracy of the wavelength calibration itself. Addressing this, the cost-effective and stable Fabry-Pérot (FP) etalons are an alternative to uranium-argon (UAr) lamps because they last significantly longer and have a spectrum that is ideal for supporting better wavelength calibration for very precise RV measurements. We are changing PARAS-2’s calibration system from UAr to FP. In this seminar, we will give project progress report and show laboratory testing outcomes of the FP system.

LCSR application to D+ → π+l+l−

Date: 2025-02-13
Speaker: Dr. Anshika Bansal
Venue: Room no: 469 (Main Campus)

Abstract

Flavour Changing Neutral Currents (FCNCs) in the Standard Model (SM) arise only at loop level, making them important probes for New Physics (NP). However, unlike bottom FCNCs (for example b → s l+l−), the charm FCNCs (for example c → u l+l− ) are dominated by long distance (LD) effects due to strong GIM suppression, posing significant challenges. In this talk we will explore these challenges focusing on decays D+ → π+l+l− which can be realised as the combination of the singly Cabibbo suppressed (SCS) weak transitions with the electromagnetic emission of the lepton pair. We study these LD effects using the framework of Light Cone Sum Rules (LCSR) and make predictions for the differential widths for these decays. Our findings suggest that the weak annihilation contributions are dominant, with negligible loop contributions. Finally, I relate these decays to other Cabibbo favoured and doubly Cabibbo suppressed, D(s)+ → P l+l− (P = π, K... ) decays through flavour symmetries. As a byproduct, I further discuss Ds+ → π+l+l−, which is not an FCNC but shares the topologies with D+ → π+l+l−, and can therefore be useful in better understanding of LD dynamics involved.

Solar Coronal Phenomena: Imaging X-ray Spectroscopy

Date: 2025-02-11
Speaker: Dr. Biswajit Mondal
Venue: Seminar Room # 113/114 (Thaltej campus)

Abstract

The Sun's outer atmosphere, known as the corona, is significantly hotter than its surface, presenting a long-standing scientific mystery. One hypothesis is that small, frequent bursts of energy, called nanoflares, may be responsible for this heating, though the exact mechanism remains unclear. Additionally, certain elements in the corona appear more abundant than expected, a phenomenon termed the "FIP effect," which might also be linked to coronal heating processes. Imaging X-ray spectroscopy offers a powerful method for investigating these solar mysteries. In this talk, we will explore these intriguing questions about the Sun and discuss how imaging X-ray spectroscopy can provide insights. We will introduce the Marshall Grazing Incidence X-ray Imaging Spectrometer (MaGIXS) sounding rocket experiment and its recent successful flight, designed to probe these enigmatic aspects of the Sun.

Puzzles and predictions of the left right symmetric model

Date: 2025-02-06
Speaker: Dr. Ravi Kuchimanchi
Venue: Room no: 469 (Main Campus)

Abstract

We will show that O(1) leptonic CP violation generates too large a strong CP phase in one loop RGE running, and therefore the Minimal Left Right Symmetric Model (with triplet and bidoublet Higgses) is testable regardless of the scale of parity breaking by the following prediction: The neutrino experiments will not discover leptonic CP violation in the PMNS matrix. Moreover the lepton mass hierarchy can be understood in this model if the electron mass is radiatively generated in 2 loop RGE.

Tides as a tool for deciphering internal structures of telluric planets

Date: 2025-02-05
Speaker: Prof Agnès Fienga
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Modelling the tidal deformations observed on the telluric planets is a complementary approach to any seismological data to decipher their internal structure. It provides constraints on internal heterogeneities, as well as rheological and density constraints on materials, enabling tidal 'tomography'. These constraints, coupled with thermodynamic models, allow us to establish the current structure of these objects and help us to understand their geodynamic evolution. In this seminar, we will look at the internal structures of Moon and Mars cores, the process of mantle overturn during the crystallisation of the lunar magma ocean, the persistence of a potentially molten zone in the Martian mantle and the persistence of a significant viscosity contrast between the upper mantle of Venus and the lower mantle. We will also look at the viscosity contrasts between the Martian lithosphere and asthenosphere. The challenges of characterising the existence of heterogeinities in the Moon mantle will be also addressed.

Diffuse Interstellar Bands in the Milky Way as seen by GAIA

Date: 2025-02-04
Speaker: Mathias Schultheis
Venue: Room No. 113, Thaltej

Abstract

Diffuse interstellar bands (DIBs) are interstellar absorption features originating from the interstellar medium, quasi-consensually attributed to large organic molecules. DIBs exist in the optical and in the infrared. Most of the DIBs show a tight relation with interstellar reddening, and can therefore be used as an excellent tracer of the ISM. Beside the equivalent width of the DIBs, radial velocities profiles can be derived and be used to study e.g the Galactic rotation curve of the carrier. I will present the capacity of the Gaia-Radial Velocity Spectrometer (RVS) in Gaia DR3 to reveal the spatial distribution of the unknown molecular species responsible for the most prominent DIB at 862\,nm in the RVS passband exploring the Galactic interstellar medium within a few kiloparsecs from the Sun. Nearly 500.000 DIB measurements have been obtained in a homogeneous way covering the entire sky, making it the largest sample of DIB measurements so far. I compare spatial distributions of the DIB carrier with interstellar reddening and find evidence that DIB carriers are present in a local bubble

Design and development of PRATHIMA electronics subsystem for LuPEX/Chandrayaan-5 Rover

Date: 2025-01-31
Speaker: Chandan Kumar
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Permittivity and Thermophysical Instrument for Moon’s Aquatic Scout (PRATHIMA) is an instrument onboard ISRO-JAXA LuPEX Rover. PRATHIMA experiment consists of three main sub-systems: (a) a permittivity probe that will be deployed into ~50 cm of the lunar surface (in a pre-drilled borehole), (b) electronics and (3) a deployment mechanism. The Probe consists of pairs of electrodes, which consist of a pair of transmitters and receivers. The complex permittivity of the Lunar Regolith over the low-frequency range (e.g. 1Hz-10 kHz) by measuring the mutual impedance between the transmitter and receiver electrodes. The subsurface complex permittivity (i.e., dielectric constant and conductivity) is derived from the measured phase and amplitude of the mutual impedance. The dielectric constant of water ice embedded in Lunar regolith strongly depends on the frequency in the 10 Hz-10 KHz range and temperature. The design aspects and its development status will be presented in the seminar.

Non-Fermi Liquid Transport in Semimetals and Strongly Correlated Systems

Date: 2025-01-30
Speaker: Dr. Abhishek Samanta, IIT Gandhinagar
Venue: Room no: 469 (Main Campus)

Abstract

The Hall coefficient traditionally measures the density of charge carriers in metals, via Drude’s inverse carrier density relation. However, this relation may break down due to intriguing Fermi surface topology or strong electronic interaction. Using a recently developed thermodynamic formalism, we study deviations of the Hall coefficients from Drude's relation in (1) semimetals (e.g., Weyl, nodal-line) and (2) the Hubbard model. Our calculations explain the "Hall anomaly", characterized by a divergence of the Hall coefficient near half-filling and an abrupt sign change, observed in cuprate experiments. Finally, I will briefly discuss similar anomalies in thermopower, studied via the calculation of the Seebeck coefficient of strongly interacting systems.

Biogeochemistry of the Arabian Sea since JGOFS

Date: 2025-01-28
Speaker: Prof. Sanjeev Kumar
Venue: Ground Floor Lecture Hall

Abstract

The Arabian Sea is one of the most productive oceanic basins of the world. Most of our understanding related to physical, chemical and biological aspects of the Arabian Sea was developed during the Joint Global Ocean Flux Studies (JGOFS) program in the early 90s. This talk will delve upon some of the landmark findings of that era and progress made, if at all, since then.

Transmitter electronics of Permittivity and Thermophysical Instrument for Moon’s Aquatic Scout (PRATHIMA)

Date: 2025-01-24
Speaker: Sushil Kumar
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

PRATHIMA is one of the selected payloads for the LUPEX/Chandrayaan-5 mission. Its primary objective is to detect and quantify regolith-bound water-ice on the lunar surface/subsurface in the vicinity of the landing site, along the traverse of the rover. The working principle of PRATHIMA involves measuring the dielectric permittivity of water-ice at low frequencies, as water-ice exhibits a significantly high dielectric permittivity in this range. Therefore, a low-frequency sinusoidal signal can be used to excite a medium to study the presence of water-ice content mixed with the regolith.A transmitter electronics system has been designed to generate a programmable low-frequency sinusoidal signal using an FPGA-based Direct Digital Synthesis (DDS) algorithm.

Exploring the Dynamics of Oxygen Minimum Zones in the Bay of Bengal over the last 25 ka

Date: 2025-01-21
Speaker: Dr. Deepak Kumar Rai
Venue: Ground Floor Lecture Hall

Abstract

Anthropogenic warming has significantly reduced oceanic oxygen levels, raising concerns about the expansion of Oxygen Minimum Zones (OMZs) and their impact on marine habitats. The northern Indian Ocean hosts one of the world's three major OMZs, with pronounced oxygen-deficient conditions in the northeastern Arabian Sea. In this region, dissolved oxygen levels drop below 10 nM at intermediate depths, intensifying anaerobic processes such as denitrification and ammonium oxidation (anammox). These processes contribute to the loss of bioavailable nitrogen and nitrous oxide production—a potent greenhouse gas. In contrast, while dissolved oxygen concentrations in the Bay of Bengal fall below 20 μM, evidence for nitrogen loss processes remains inconclusive. However, the Bay of Bengal OMZ is considered to be at a geochemical tipping point, where further oxygen depletion—driven by anthropogenic nutrient input or climate change—could amplify its role in the marine nitrogen cycle by triggering nitrogen loss processes. Natural mechanisms influencing OMZ variability, aside from global warming, remain poorly understood, likely due to limited observations that are already influenced by anthropogenic signals. Therefore, it is essential to explore long-term OMZ variations under diverse climatic conditions through paleo reconstructions, which can provide crucial insights into the natural variability of OMZs, aiding in more accurate future predictions. In this talk, I will discuss the current understanding of OMZ dynamics in the northern Indian Ocean and highlight key research gaps in the field.

In-In EFT, the In-Out way

Date: 2025-01-21
Speaker: Prof. Namit Mahajan
Venue: Room no: 469 (Main Campus)

Abstract

In-In correlators are the natural quantities in time dependent settings like cosmology or in non-equilibrium situations when the interest in not in scattering matrix elemnts but rather expectation values. The talk will describe an attempt to have an effective field theory (EFT) description for In-In correlators in terms of the more familiar In-Out formalism routinely used for S-matrix calculations.

Characterization of Multichannel SDD X-Ray Spectrometer with ASIC Readout

Date: 2025-01-17
Speaker: Nishant Singh
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

In the seminar, I will present the development of a multichannel Silicon Drift Detector (SDD) based X-ray spectrometer with application-specific integrated circuit (ASIC) readout aimed at flying in future space missions. The multiple channels facilitate the spectrometer to have a large detection area, allowing the detection of faint X-ray sources. The spectrometer is designed to readout the signal from eight SDDs through a VErsatile Readout for Detector Integration (VERDI) ASIC with high energy resolution in the 1-25 keV energy range. The spectrometer provides an X-ray spectrum for each detector simultaneously. Initially, the system is tested with five SDDs and shown that the spectrometer provides the energy resolution of ~148 eV at 5.9 KeV when SDDs are cooled to -35oC. We have also assessed the system’s performance for different detector operating temperatures and pulse shaping times. The detailed design and the performance assessment of the spectrometer will be presented in the seminar.

Radio eyes for the Sun, Heliosphere and Ionosphere: Status and plans for the LOFAR2.0 era.

Date: 2025-01-17
Speaker: Dr. Pietro Zucca
Venue: USO Seminar Hall

Abstract

The Low-Frequency Array (LOFAR) has established itself as a formidable instrument in the field of solar physics and spaceweather, providing a unique vantage point for observing the Sun, heliosphere, and ionosphere. As we transition into the LOFAR2.0 era, this abstract outlines the current status and future plans for leveraging LOFAR's capabilities, and the LOFAR IDOLS (Incremental Development of LOFAR Space-weather) project.LOFAR's current work in solar physics involves high-resolution imaging and dynamic spectral analysis, enabling detailed observations of solar radio bursts and other coronal heliosphere and ionosphere phenomena. These observations are critical for understanding the mechanisms behind solar activity and improving our predictive models of space weather events. The LOFAR IDOLS station, a dedicated space-weather science facility, has been instrumental in advancing this work. It currently provides continuous monitoring of the ionosphere and Sun, tracking disturbances that can affect space wetaher on Earth, but also the astronomical observations of LOFAR itself. The LOFAR2.0 upgrade promises to enhance these capabilities significantly. Plans include improving the sensitivity and spatial resolution of the array, and the simoultaneus observations in LBA and HBA, which will allow for even more precise and broad imaging and tracking of solar phenomena. This will enable researchers to dissect the fine structures within the solar corona and track the development of space weather events with greater accuracy. Furthermore, the LOFAR IDOLS project is set to continue observation during the period of transition to LOFAR2.0 enabling us to test the monitorning capabilities. In conclusion, the LOFAR2.0 era opens a new opportunity for solar and space weather research. With the ongoing work and future plans for the LOFAR IDOLS station and LOFAR2.0 observations, we are preparing to gain deeper insights into the Sun's influence on our space environment and to develop more robust forecasting capabilities for space weather phenomena.

Exploding Stars, Shapeshifting neutrinos, and the Synthesis of Heavy Elements

Date: 2025-01-16
Speaker: Dr. Amol V. Patwardhan, New York Institute of Technology, USA
Venue: Online--- https://imeet.vconsol.com/join/1447710668?be_auth=NTg3MTQz

Abstract

How exactly do stars explode? Where and how are the elements that we observe in the cosmos synthesized? A common theme tying these questions together is the abundant presence of neutrinos – mysterious and elusive elementary particles – in these environments. In this talk, I shall describe how neutrinos can power these magnificent cosmic explosions, i.e., supernovae, and also aid in the synthesis of heavy elements thereafter. Particular attention will be given to a longstanding open question: the origin of proton-rich isotopes in nature. I will present some interesting results from my recent work, demonstrating how a once-popular solution to this conundrum still endures, despite a decade's worth of claims to the contrary. Finally, I shall briefly discuss some peculiar behaviors of neutrinos, such as their penchant for shapeshifting (flavor oscillations), or their potential to quantum-entangle as they interact with each other in these environments.

Organic Matter Sulfurization Dynamics in Natural Systems

Date: 2025-01-15
Speaker: Dr. Tushar Adsul
Venue: Online

Abstract

The sulfurization of organic matter is a globally significant biogeochemical process with far-reaching implications for the Earth's carbon, sulfur, and oxygen cycles. This process has been a subject of intense investigation due to its role in several critical areas: (1) petroleum formation and quality, (2) the coupled global biogeochemical cycles of carbon, sulfur, and oxygen, (3) sedimentary microbial activity, and (4) the preservation of organic matter and its application in molecularly based paleoenvironmental reconstructions. Despite its significance, our understanding of organic matter sulfurization remains incomplete. One major challenge in unraveling the sulfurization process is the immense diversity of organic sulfur compounds in nature, which form via various pathways. Sulfur can be incorporated intramolecularly into organic molecules, forming cyclo-sulfur compounds such as thiophenes or thianes. Alternatively, sulfur can be added intermolecularly, leading to macromolecular moieties linked by C-Sx-C bonds. This diversity complicates efforts to establish universal mechanisms for organic sulfur formation. Another critical challenge lies in the complexity of sedimentary sulfur cycling, which involves both biological and abiological processes. The precise source of sulfur incorporated into organic matter is not well understood. Whether pore-water sulfide, polysulfides, elemental sulfur, or a combination of these sources contributes to the sulfurization process remains unclear. The interactions among these sulfur pools and organic substrates further add to the complexity of the system. The sulfurization process is particularly significant in anoxic environments, such as marine sediments, where sulfate-reducing bacteria generate hydrogen sulfide. This reactive sulfide interacts with organic matter, stabilizing it by forming sulfur-rich compounds. These compounds, such as thiophenes, are resistant to degradation and play a vital role in the long-term preservation of organic matter in sediments. Furthermore, sulfurization contributes to the formation of sulfur-rich petroleum and coal, such as the Paleogene Superhigh-Organic-Sulfur Coals of Meghalaya, India. Recent advancements in analytical techniques are opening new avenues for understanding the mechanisms of organic matter sulfurization. The use of sophisticated tools such as GC-MS/FID/FPD for organic sulfur compound identification, coupled with compound-specific sulfur isotope analysis (CSIA), enables researchers to trace sulfur fractionation at the molecular level. These techniques help establish precursor-product relationships and provide insights into the pathways of sulfur incorporation into organic matter.

The Origin of Isotopes

Date: 2025-01-10
Speaker: Mr Antariksha Mitra
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The origin of isotopes plays a cruicial role in understanding the chemical enrichment of the Universe. Isotopes are formed through nucleosynthesis processes in stars, including stellar burning, supernovae, and neutron star mergers. These processes distribute isotopes into the interstellar medium (ISM), influencing the evolution of galaxies. Galactic Chemical Evolution (GCE) provides a framework to model the production, distribution, and recycling of isotopes over cosmic time, driven by processes such as star formation, stellar feedback, and gas inflow/outflow. In this seminar, I will discuss the primary sources of isotopes, the physics of their nucleosynthesis, and the mechanisms by which they are transported and mixed within galaxies. The talk will also explore the connection between isotope studies and the broader understanding of the Milky Way's formation and evolution.

On the Propagation of Shock Waves in the Transition Region and the Corona

Date: 2025-01-10
Speaker: Mr. Ravi Chaurasiya
Venue: USO Seminar Hall

Abstract

The chromosphere exhibits various acoustic waves that are generated in the photosphere or deeper layers due to convective motions. As these waves encounter the steep density gradient between the photosphere and the chromosphere, they transform into shock waves, often characterized by a sawtooth pattern in Î»-time plots of chromospheric spectral lines, such as HÎ± and Ca II. In this study, we investigate the formation and propagation of these shock waves in the chromosphere, examining their possible implications in the higher solar atmosphere using observations from the Multi Application Solar Telescope (MAST), the Swedish 1-meter Solar Telescope (SST), the Interface Region Imaging Spectrograph (IRIS), and the Solar Dynamics Observatory (SDO). Our results show that these shock waves are predominantly observed in or near magnetic flux concentration regions and can propagate at least up to the transition region. In this talk, I will discuss the identification of these shock waves, their propagation characteristics, and their potential implications for coronal dynamics.

Tracing Cosmic Origins: Unveiling Element Formation Through Stellar Archaeology

Date: 2025-01-09
Speaker: Pallavi Saraf
Venue: Online: https://imeet.vconsol.com/join/8509176600?be_auth=NjMwMzQ4

Abstract

The origins and distribution of chemical elements in the Universe have long been a subject of investigation, with many unresolved questions remaining. The oldest stars in our Milky Way are rare relics from the early Universe, preserving the chemical imprints of the first stars and supernova explosions. These stars are crucial in addressing questions about element formation processes that occurred around 13 billion years ago. I will explain on how I employ "Stellar Archaeology": the use of observations and analysis of the chemical properties of the oldest stars in Galaxy, to answer outstanding questions about the early Universe and the origins of the chemical elements in the Cosmos. One of the significant unanswered questions in astrophysics is the site of the rapid neutron-capture process (r-process). While the optical counterpart AT 2017gfo of the kilonova GW 170817 did provide evidence of the r-process in neutron star mergers, important details are still unsolved. Neutron star mergers alone seem to be unable to explain r-process enrichment in the Universe, and there are still open questions with respect to their time scale. I will discuss some of the results from observations of r-process stars with the Gran Telescopio Canarias (GTC) and the Very Large Telescope (VLT), as well as CEMP-r/s stars observed with the KECK telescope and VLT. Additionally, I will share findings from the HESP-GOMPA survey conducted by our group. Finally, I will discuss how my expertise aligns with the facilities at the Physical Research Laboratory (PRL), such as PARAS-2.

Electron Density Mapping: Insights from Radio and In-Situ Observations & EUHFORIA Modeling

Date: 2025-01-09
Speaker: Ms Ketaki Despande
Venue: USO Seminar Hall

Abstract

Mapping the coronal electron density remains a challenging task, as we still rely on rather old 1D electron density models, most of which are derived from remote sensing observations and lack validation with in situ measurements. The novel observations from Parker Solar Probe (PSP) provide a unique opportunity to validate these models and enhance space weather modeling capabilities. In this study, we analyze type III radio bursts observed during PSP’s second perihelion. By employing radio triangulation, we estimate the 3D radio source positions and map the electron densities along the burst propagation path. These results are then compared with in situ electron density measurements from PSP. Additionally, we use EUHFORIA (European Heliospheric Forecasting Information Asset) to model electron densities at the PSP location and the radio source positions. Our findings indicate that bursts occurring within a few minutes from the same source can exhibit significantly different propagation paths. A comparison between radio-derived and in situ densities reveals a discrepancy of one order of magnitude. We also perform simulations using GONG and ADAPT-GONG magnetic maps as input. Both simulations suggest that type III bursts propagate along higher-density regions; however, results obtained with ADAPT-GONG maps show a better match with PSP in situ densities and predict higher density values overall. These results highlight the importance of validating remote sensing electron density models with in situ observations and demonstrate the impact of different magnetic field inputs on space weather modeling. The improved agreement with ADAPT-GONG maps suggests that incorporating more dynamic and data-driven models can enhance the accuracy of electron density estimations, ultimately improving our understanding of solar wind structures and radio wave propagation in the heliosphere.

Probing accretion process and emission mechanism of X-ray pulsars in multi-wavelength

Date: 2025-01-08
Speaker: Manoj Mandal
Venue: Online: https://imeet.vconsol.com/join/8880252012?be_auth=MjU0NzIy

Abstract

The timing and spectral studies have been carried out for several X-ray pulsars to probe the emission mechanism, accretion process, and spectral states. The timing and spectral properties evolve significantly above the critical luminosity. The accretion mode, beaming patterns, and emission mechanism evolve significantly above this luminosity. A significant evolution of temporal and spectral properties is observed during the state transition for X-ray pulsars, 1A 0535+262 and RX J0440.9+4431. A variable cyclotron line was detected from 1A 0535+26, and the magnetic field was estimated using the cyclotron line energy. The variation of the cyclotron line is probed. The significant evolution of line energy with luminosity was observed, which may be linked with the transition of state in the X-ray pulsars. The unstable burning of accreted material on the surface of neutron stars induces thermonuclear (Type-I) bursts. Thermonuclear bursts can be used to probe several properties of neutron stars. Multiple thermonuclear bursts were detected from MAXI J1816−195 and Aql X-1. The details of timing and spectral properties are studied during the X-ray bursts. The estimated mass accretion rate indicates the stable burning of hydrogen via a hot CNO cycle during the bursts.

A 3D Thermophysical model for Temperatures and Thermophysics at Prospective Sites on Mars

Date: 2025-01-08
Speaker: K. Samadhanam Raju
Venue: online

Abstract

Existing thermal models of Mars, such as the KRC 1D model, lack the ability to account for complex heat transport processes, topographical variations, and environmental factors like dust storms and surface changes. This study addresses these gaps by developing a 3D thermophysical model that integrates lateral heat transport, accurate topography from MOLA DEM, and Martian-specific conditions, including its thin CO₂ atmosphere and thermal inertia. The model provides detailed insights into localized thermal variations at prospective landing sites, enhancing mission planning and advancing our understanding of Mars' thermal behavior and geological history.

Are humans now the dominant geological agent?

Date: 2025-01-08
Speaker: Prof. Stephen Tooth Dept. Geography & Earth Sciences Aberystwyth University, Wales
Venue: Ground Floor Lecture Hall

Abstract

The Anthropocene is a term that has been proposed to account for the arguably ‘dominant’, ‘overriding’ or ‘overwhelming’ role of human activities in shaping the Earth’s geological record. Some academics have argued that we have now exited from the Holocene (the present interglacial time division) and entered a new geological age, one now defined by humanity’s profound influence on Earth’s atmospheric, biological, and earth surface processes. Although a subcommittee of the International Commission on Stratigraphy (ICS) has recently decided that the Anthropocene will not become an official epoch in Earth’s geological timeline, the term itself will endure because for many people it encapsulates the sense that humans are now a fundamental part of the Earth system and integral to its processes. The Anthropocene proposal has many philosophical, ethical, moral and practical implications, and will continue to generate lively academic debate across the natural sciences, social sciences, humanities and arts, while also providing scope for greater public engagement with environmental decision making. Adopting a geoscience perspective, this talk will outline the case for and against an Anthropocene, and outline ways in which we might compare landscape shaping by human activities and natural processes.

Anderson localization in QFT and hierarchies from nonlocality

Date: 2025-01-07
Speaker: Dr. Ketan Patel, THEPH
Venue: Room no: 469 (Main Campus)

Abstract

It was shown in [1710.01354] that disordered local interactions in theory space can localize mass eigenstates (analogous to Anderson localization in disordered lattice) enabling exponentially hierarchical couplings in QFT. In this talk, I shall show that such theories can also produce multiple massless modes. Subsequently, deterministic nonlocality can give rise to hierarchies that are qualitatively distinct from the original proposal.

Loss Pathway of organic Carbon in the Himalayan Permafrost Region

Date: 2025-01-07
Speaker: Rahul Kumar Agarwal
Venue: Ground Floor Lecture Hall

Abstract

Soil organic carbon (SOC) stored in permafrost regions represents a critical component of the global carbon cycle. Climate change significantly influences the distribution and dynamics of carbon across Earth's systems. It is widely believed that climate change is driving substantial carbon loss from high-latitude and high-altitude soils, including permafrost areas. However, the pathways through which soil organic matter is lost remain poorly understood, and the extent of older organic matter degradation, particularly in the high-altitude Himalayan permafrost regions, is not well quantified. To address this gap, we measured radiocarbon content in soil organic carbon, soil CO2, and soil CH4 across various depths of a peat profile located at approximately 4500 meters above mean sea level in the Sikkim Himalayas. In this talk I will discuss about the basics of mountain permafrost, radiocarbon dating of soil methane, and loss pathway of organic carbon in the permafrost region.

Mathematical Framework for Dust Dynamics under Different Forces

Date: 2025-01-03
Speaker: Ms. Aanchal Sahu
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Interplanetary Dust Particles (IDPs) are a fundamental constituent of the Solar System, originating from diverse sources such as the Asteroid Belt, Kuiper Belt, Oort Cloud, and comets. It manifests in phenomena like Zodiacal Light and Meteor showers. As IDPs migrate inward toward the Sun, their dynamics are governed by a combination of gravitational and non-gravitational forces, including Poynting-Robertson drag, solar radiation pressure, and solar wind drag, which induce perturbations in their orbital elements. In this seminar, I will discuss the mathematical framework for orbital perturbations and the governing force equations, derived from the principles of celestial mechanics. The variation in orbital elements due to the governing forces will be analyzed, along with the obtained results. In addition to this, the method for estimating the dust flux on planetary bodies will be explored, with a focus on insights derived from our research.

Probing the Cold Molecular Gas in Luminous Dusty Star-forming Galaxies at z~1-6

Date: 2025-01-02
Speaker: Ms. Prachi Prajapati
Venue: Seminar Room No. 113, Thaltej

Abstract

The galaxies and star formation we see at present are attributed to a long history of galaxy formation and evolution. Reconstructing back in time the physical processes that led to the existing galaxies and explaining them in terms of different properties of the matter is one of the prime goals of the observational cosmology. In particular, studying the molecular gas content of high-redshift dusty star-forming galaxies (DSFGs) is of utmost importance for observationally confirming the galaxy formation and evolution theories. Observing the gas with low excitation leads to better mass estimates and also helps in deriving the gas and dust properties of these galaxies more accurately. Having a large and diverse sample of DSFGs for such a study plays an important role in setting up statistically significant trends within the DSFG population and in determining whether or not there are significant differences in the gas properties of DSFGs compared to other populations. This talk will be focused on the VLA large program to observe CO (1–0) in high-redshift DSFGs (0.8 < z < 6.5) for deriving insights on the cosmic star formation history.

Complete escape from localization on a hierarchical lattice: A Koch fractal with all states extended

Date: 2025-01-02
Speaker: Sougata Biswas, Presidency University
Venue: Online--- https://imeet.vconsol.com/viewer/1718585506?be_auth=NTIwNzYy

Abstract

"An infinitely large Koch fractal is shown to be capable of sustaining only extended, Bloch-like eigenstates if certain parameters of the Hamiltonian describing the lattice are numerically correlated in a special way, and a magnetic flux of a special strength is trapped in every loop of the geometry. We describe the system within a tight-binding formalism and prescribe the desired correlation between the numerical values of the nearest-neighbor overlap integrals, along with a special value of the magnetic flux trapped in the triangular loops decorating the fractal. With such conditions, the lattice, despite the absence of translational order of any kind whatsoever, yields an absolutely continuous eigenvalue spectrum and becomes completely transparent to an incoming electron with any energy within the allowed band. The results are analytically exact. An in-depth numerical study of the inverse participation ratio and the two-terminal transmission coefficient corroborates our findings. Our conclusions remain valid for a large set of lattice models, built with the same structural units, but beyond the specific geometry of a Koch fractal, unraveling a subtle universality in a variety of such low-dimensional systems. Reference: S. Biswas and A. Chakrabarti, Physical Review B 108, 125430 (2023)."

2024

Lunar Neutron Leakage Spectrum and its sensitivity to the presence of hydrogen in the lunar subsurface

Date: 2024-12-27
Speaker: Ms. Shipra
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The Moon's absence of a magnetic field and atmosphere exposes its surface to ionizing radiation, including solar wind, SEPs, and galactic cosmic rays. High-energy galactic cosmic rays interact with the lunar surface, generating fast neutrons through nuclear reactions. These fast neutrons are moderated by collisions with the nuclei of lunar soil and leak out, acting as messengers of the soil composition. Studying this neutron leakage spectrum can reveal important information about the Moon’s soil composition and near-surface hydrogen abundance. In this seminar, I will discuss the production and moderation processes of neutrons inside the lunar surface.

Observational determination of magnetic helicity and energy flux in the solar active regions.

Date: 2024-12-27
Speaker: Mr. Dinesh Mishra
Venue: USO Seminar Hall

Abstract

Magnetic helicity measures the degree of twisting of magnetic flux tubes, the shearing of magnetic arcades, and the interlinking of magnetic flux tubes. It plays an essential role in understanding the evolution of magnetic fields in the solar active regions and the triggering mechanism of solar transients that take place in the solar atmosphere, viz., flares and CMEs. In this talk, I will discuss about the estimation of magnetic helicity and the associated energy flux in the solar active regions using the observed photospheric vector magnetic fields and their importance.

Introduction to Solar Flares and Magnetic Reconnection.

Date: 2024-12-26
Speaker: Ms. Simrat Kaur
Venue: USO Seminar Hall

Abstract

Solar flares are sudden explosive events on the Sun that release energy through heating, electromagnetic radiation, and the acceleration of charged particles. These events are believed to be the manifestations of the magnetic reconnection process and can release energy ranging from 10^23 erg to 10^32 erg. In this seminar, I will discuss Solar flares and how they are connected to magnetic reconnection.

The Journey of Star Formation: From Collapsing Cloud to Accreting Protostar

Date: 2024-12-26
Speaker: Kushagra Srivastav
Venue: Seminar Room No. 113, Thaltej

Abstract

Star formation is a fundamental and vital process of molecular cloud evolution and the creation of stellar systems. Stars are born within the dense, compact, and low-temperature regions of molecular clouds called cores. These dense cores are the sites that eventually lead to the formation of a protostar, surrounded by a protoplanetary disc and an infalling envelope. Understanding the various stages, from the collapsing cores to the formation and growth of a protostar, requires understanding the physical and dynamic processes involved. In this talk, I will discuss the various stages of star formation and the role of different physical processes involved and also touch upon the evolution of a protoplanetary disk and the accretion from the disk to the star.

Solar Flares: Multi-wavelength Observations

Date: 2024-12-24
Speaker: Mr. Vishwa Vijay Singh
Venue: USO Seminar Hall

Abstract

Solar flares are among the most energetic events in the solar system, characterized by the sudden release of magnetic energy stored in the Sun’s corona. These phenomena emit radiation across the entire electromagnetic spectrum, from radio to γ-rays. Multi-wavelength observations provide a comprehensive understanding of the physical processes driving solar flares, including energy release, particle acceleration, plasma heating, and large-scale coronal restructuring. In this seminar, I will highlight the complementary nature of multi-wavelength observations in understanding the temporal and spatial evolution of solar flares. Additionally, we will discuss the role of magnetic reconnection and its association with large-scale phenomena such as coronal mass ejections (CMEs).

Speleothem Paleoclimatology: Insights from Clumped and Triple Oxygen Isotopes

Date: 2024-12-24
Speaker: Ms. Aishwarya Singh
Venue: Ground Floor Lecture Hall

Abstract

A multitude of creditable terrestrial paleoclimate reconstructions have been done using oxygen isotope ratios in speleothems based on the temperature dependency of the carbonate-water isotope exchange equilibrium. However, these interpretations remain inadequate due to improper constraints on drip-water isotopic compositions and possible kinetic isotopic effects. Moreover, the variations in the oxygen isotopes of speleothems are affected by both temperature and precipitation, making it challenging to estimate their individual contributions. Clumped isotope thermometry, based on the abundance of 13C-18O bonds, is capable of constraining the growth temperature of carbonates independent of the isotopic composition of drip water. The clumped-derived temperature can be combined with oxygen isotopes to constrain the paleo-temperature and paleo-precipitation values, subject to the maintenance of thermodynamic equilibrium. To validate the latter, triple oxygen isotopes will be analysed alongside clumped isotopes in modern speleothems. Triple oxygen isotopes also present a potential strategy to decipher the various fractionation processes from the moisture source, en route to its final sink. In this seminar, I will discuss how these emerging techniques can be used to significantly improve our understanding of the paleoclimate beyond what was possible with the conventional methods.

Rim-breached Craters: Insights into fluvial activities on Mars

Date: 2024-12-20
Speaker: Rishav Sahoo
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

On Mars, there are a substantial number of craters whose rims are breached due to external activity like catastrophic outflow channels, river channels, and valley networks. These rim-breached craters are the potential targets till date for the Mars rover mission due to their enriched fluvial origin deposits. The dimensions of these breaches—specifically breach width and breach height—are directly related to the volume of water that interacted with the crater rims over time. Understanding these breach parameters is essential for estimating the volume of water involved, the rate of discharge, and the velocity of water flow throughout Mars's geological history. This study concentrates on the rim-breached craters located in the Chryse Planitia region, which features various types of fluvial valley networks, particularly those associated with the Valles Marineris region on Mars.

Properties of Sunspot Umbral Dots

Date: 2024-12-20
Speaker: Mr. Amit Chaturvedi
Venue: USO Seminar Hall

Abstract

Umbral Dots (UDs) are small, bright structures seen in the dark umbral core of pores and sunspots. They represent convective intrusions in the highly magnetized surroundings of the sunspot's umbra. In this talk, I will review the photometric, kinematic, and magnetic properties of UDs from high resolution ground- and space-based observations.

Dynamics of Solar Corona Heliospheric Interaction

Date: 2024-12-19
Speaker: Ritik Dalakoti
Venue: Room No. 113, Thaltej

Abstract

The lower solar corona exhibits significant dynamic activity across various scales, with magnetic features continuously forming and disappearing on the Sun's surface. Understanding the relationship between these features and the heliosphere is crucial for understanding the heliosphere and predicting the flow of plasma within it. This knowledge is essential for forecasting space weather accurately. In this study, we investigate an M-class solar flare from which plasma eventually propagated into the heliosphere. We examine the evolution of First Ionization Potential (FIP) elements during the flare using the soft X-ray spectrum from the Solar X-ray Monitor aboard Chandrayaan-2. Additionally, we analyse in situ particle data to determine whether the evolution of FIP elements can be observed at 1 AU or other heliospheric locations.

Exploring small-scale transient brightenings in the context of solar atmospheric heating

Date: 2024-12-19
Speaker: Mr. Hasil Dixit
Venue: USO Seminar Hall

Abstract

Effective theories at finite temperature

Date: 2024-12-19
Speaker: Prof. Subhendra Mohanty, IIT Kanpur
Venue: Room no: 469 (Main Campus)

Abstract

Effective theories offer an economical way to test the predictions of diverse UV complete theories in low energy experiments. The finite temperature formulation of effective theories is needed for applications in cosmology and collider experiments in phase transitions, quark gluon plasma, Casimir effect etc. I will discuss a way to formulate effective theories at finite temperature using the Heat Kernel Method which involves the calculation of finite temperature corrections to the Wilson coefficients. I will illustrate the results with a calculation of Coleman-Weinberg potential for the Higgs-Effective field theory and apply it in testing the nature of phase transition from different extensions of the standard model. Of particular interest is the emergence of Polyakov loops as a parameter which has applications in phase transitions and spin-systems in condensed matter.

Terrestrial Recycling and its linkages to Meteorology: Insights from stable water isotopes in vapor in conjunction with Machine Learning, at a high-altitude site in western India

Date: 2024-12-17
Speaker: Akash Ganguly
Venue: Ground Floor Lecture Hall

Abstract

The implications of a warming climate have raised awareness towards potential hydrological challenges, with a conspicuous rise in both frequencies, as well as intensity of extreme events. Moisture recycling, accounting for ~67 (40) % of the net terrestrially sourced precipitation globally (India), is a vital component of the water cycle. The recycled moisture is primarily contributed via two major sources- i) direct evaporation from surface reservoirs ii) transpiration from dense forests. However, delineating their relative contributions has proved challenging using conventional tools. In this study, we leverage stable water isotopes in vapor from the highest point in western India to track moisture transport, and constrain the role played by the regional meteorology in governing terrestrial recycling during pre-monsoon. The study location (Gurushikhar, Mt. Abu) perfectly aligns with our objective, with it being a natural bio-diversity hotspot, with ~288 sq. km. of densely forested terrain, and very low levels of air pollution. A novel statistical-machine learning framework is developed to quantitatively infer the non-linear relationships, governing the high-dimensional coupled land-atmospheric system. Here, we find 1) A strong inverse relationship between wind-speed, and deuterium excess, suggesting increased role of kinetic processes. 2) Dominant role of valley recycling, with ~30-40 % contribution from transpiration alone. 3) Elevated levels of tropospheric ozone (> 65 ppbv.) suppressing transpiration rates, resulting in up to 2 ‰ depletion in δ18O. 4) Possible signs of upper atmospheric coupling via waves, extending to ~ 10 km (above msl) 5) Development of a robust, accurate ML model with mae ~ 3.50 ‰ in δ18O, using only meteorological inputs. This study highlights the benefit in using stable water isotopes in vapor, since they can be leveraged to better understand linkages between terrestrial recycling, and regional hydro-meteorology. This brings to light the important role played by the dense vegetation cover around Mt. Abu, acting as nature’s pump and enhancing terrestrial recycling. This is of even more significance in the tropics, given the rapid loss of wetlands, and forest cover in the developing countries located in the region.

Solving the strong CP puzzle through Radiative mass mechanism

Date: 2024-12-16
Speaker: Gurucharan Mohanta, SRF
Venue: Room no: 469 (Main Campus)

Abstract

I will briefly outline the radiative mechanism for fermion mass generation and focus on how it can address the strong CP problem. To do this, the mechanism is implemented within a parity-invariant Left-Right symmetric framework. In this setup, loop-induced fermion masses arise from corrections involving a new flavor-non-universal gauge boson and heavy fermions. The required non-universal U(1) symmetry for the mechanism is an all-fermion version of the $L_\mu - L_\tau $ symmetry. The minimal model predicts that the mass of the U(1) gauge boson and the scale of right-handed sector breaking are of the same order. This leads to a strong CP phase of the order of $10^{-14} $.

Improving Solar Wind Forecasting Model Over the Phase of Solar Cycle - Source Surface Height Optimization and Magnetogram Impact

Date: 2024-12-16
Speaker: Mr. Sandeep Kumar
Venue: USO Seminar Hall

Abstract

The operational solar wind velocity prediction models used by the community are based on the Potential Field Source Surface (PFSS) model of the magnetic field. The output of PFSS serves as input in the heliospheric models to provide solar wind velocity predictions at L1. Previous studies in the context of the prediction of open magnetic flux observed at L1 have suggested different source surface heights ($R_{ss}$) in the PFSS model at different phases of the solar cycle (SC). We investigate the effects and necessity of optimizing the $R_{ss}$ in the PFSS model in the context of its use in the popular Wang Sheeley and Arge (WSA) model for solar wind velocity prediction. We used Heliospheric Upwind Extrapolation (HUX) to extrapolate solar wind velocity in the heliosphere. We performed a study of 16 Carrington Rotations (CR) at different phases of the SC24 and SC25, using different types of magnetograms and WSA model parameters. We combine the coronal models (PFSS+WSA) with the heliospheric model (HUX) to predict solar wind velocity at L1 in our framework, i.e., PFSS+WSA+HUX. Our study suggests using a higher $R_{ss}$ ($3.0$ $R_\odot$) compared to the conventional $R_{ss}$ (2.5 $R_\odot$) near the solar minimum, resulting in an increase in the average performance of the framework. We found that the improved performance of the framework by 2 times with zero-point corrected maps, as compared to the standard full Carrington maps, can be attributed to its capability to capture the global magnetic field. This was also confirmed by comparing the extrapolated global magnetic field structures with the large-scale corona observed in the extended field of view of the PROBA2/SWAP images.

Vacuum Ultraviolet Photolysis of Clathrate Hydrates under Cometary Conditions

Date: 2024-12-13
Speaker: Gaurav Vishwakarma
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Clathrate hydrates (CHs), naturally occurring in high-pressure terrestrial environments, have also been identified in interstellar conditions, where they are thought to play a significant role in the chemistry of icy bodies. Despite their importance in astrochemical models, the interactions of CHs with ultraviolet (UV) radiation remain poorly understood. In this study, we employed reflection absorption infrared spectroscopy to explore UV photolysis and subsequent thermal evolution of CHs under ultrahigh vacuum (~10⁻¹⁰ mbar) and cryogenic temperatures. Our findings demonstrate that CHs serve as molecular reservoirs, preserving volatile species while acting as microreactors that facilitate unique chemical transformations. Notably, UV-photolyzed CHs exhibited a remarkable ability to nucleate new CHs of simple molecules upon warming—a phenomenon not observed in amorphous ice analogs. These results emphasize the distinctive role of CHs in shaping photochemical pathways and retaining photoproducts under simulated interstellar conditions. I will discuss these findings in detail during my presentation, highlighting their implications for both laboratory astrochemistry and our understanding of icy environments in space.

Uncovering the hidden physical structures and protostellar activities in the Low-Metallicity S284-RE region: results from ALMA and JWST

Date: 2024-12-12
Speaker: Omkar Jadhav
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Over the past decade, Spitzer and Herschel observations have provided invaluable opportunities to explore key structures in star-forming regions, such as bubbles and filaments. With the advent of the James Webb Space Telescope (JWST) and the Atacama Large Millimeter/submillimeter Array (ALMA), researchers have access to a powerful multi-wavelength approach, which can be used to investigate the dust and gas structures around embedded protostars in exceptional detail and to study distant star-forming sites. We present an observational study of the S284-RE region (d ~5.0 kpc), a low-metallicity area associated with the extended S284 HII region. The S284 region is characterized by features such as filaments, pillars, and globules, which are hallmarks of star-forming regions shaped by stellar feedback. Multi-scale and multi-wavelength datasets are used to explore the underlying physical structures and protostellar activities in this site. In this talk, I will provide a detailed overview of our findings and their implications for understanding the physical processes driving star formation in S284-RE.

A leisurely walk through few exotic manifestation of interacting spin systems

Date: 2024-12-11
Speaker: Dr. Saptarshi Mandal
Venue: Room no: 469 (Main Campus)

Abstract

In the talk we discuss some of the fascinating aspects of frustrated magnetism in a few systems of our interest. We begin with a discussion of the origin of frustration in model systems through examples of geometric and exchange effects. The manifestation of frustration giving degenerate ground states, order-disorder phenomena through quantum fluctuations are explained in the Hollandite lattice system. Next the ground state of varieties of systems following ice rules are explained and how emergent electrodynamics is obtained are outlined. Finally we introduce Kitaev model and explain the effect of frustration and give a pedagogical exposition to abelian and non-abelian anyons or Majorana fermions obtained in this system.

Estimation of fine particulate matter and aerosol acidity at Ranchi, India

Date: 2024-12-10
Speaker: Dr. Abisheg Dhandapani
Venue: Ground Floor Lecture Hall

Abstract

The annual PM2.5 concentration was 67 ± 46 μg m-3 at Mesra, Ranchi, varying seasonally. There was a significant underestimation in MERRA-2-derived PM2.5, and machine learning techniques were used to overcome the challenge. Further, water-soluble inorganic ions accounted for 50.5% of PM2.5, and the annual mean pH estimated using ISORROPIA was 1.97 ± 0.8 units. Secondary aerosols formation (45%) and a combination of coal combustion and dust sources (10%) were the primary sources of PM2.5 identified using PCA.

Advances in Satellite Radar Imaging

Date: 2024-12-06
Speaker: Rajiv Ranjan Bharti
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Recently, IIRS Dehradun conducted the Structured Training Program (STP). The theme of the STP was "Advances in Satellite Radar Imaging". 28 Scientists/Engineers from ISRO/DOS Centers participated in the program. The programme covered the basics of radar remote sensing and its applications like natural resources management, agriculture, and infrastructure planning, disaster management and planetary exploration. This seminar will cover a brief discussion based on the lectures given by various faculty members in the STP.

An X-ray Perspective on Multi-scale Solar Flares: Spectroscopy to Polarimetry

Date: 2024-12-06
Speaker: Dr. Mithun Neelakandan P S
Venue: USO Seminar Hall

Abstract

Solar flares have a wide range of intensity scales ranging from large X-class flares to microflares to hypothesized nanoflares that may be responsible for coronal heating. Investigations of multi-scale solar flares, from large flares to the smallest microflares, are key to the missing pieces in our understanding of the flaring process and coronal heating. As the flaring plasma and accelerated electrons emit profusely in soft and hard X-rays, X-ray spectroscopic observations offer the most direct diagnostics of the thermal and non-thermal particle populations in flares and, thus, insights into the energy release mechanisms in flares. Solar X-ray Monitor (XSM) onboard the Chandrayaan-2 mission provides disk-integrated X-ray spectral measurements of the Sun in the energy range of 1-15 keV, with a high dynamic range to observe sub-A class micro flares to large X-class flares. XSM has recently completed five years of continuous solar observations and in this talk I will highlight some of the major results using XSM observations on various aspects of multi-scale solar flares. I will also introduce other recently operational solar soft X-ray spectrometers on other missions and on the advantages of simultaneous analysis of soft X-ray spectra with the hard X-ray spectra from instruments such as Solar Orbiter STIX and Aditya L-1 HEL1OS. Going beyond spectroscopy, I will also discuss the potential of X-ray polarimetric observations of solar flares and our efforts towards a small satellite experiment, which would also be a pathfinder to an X-ray astronomy mission.

Surface Tension of a Topological Phase

Date: 2024-12-06
Speaker: Dr. Adhip Agarwala
Venue: Room no: 469 (Main Campus)

Abstract

Metastable phases, in general, are unstable to nucleating droplets of the order defining the global free energy minima. However, whether such a droplet grows or shrinks relies on a competition between the surface tension and bulk energy density. We study the role of coupling a topological fermionic field to a scalar field undergoing such nucleation processes. We find that existence of nontrivial fermionic boundary modes on the nucleating droplets leads to substantial quantum corrections to the surface tension thereby modifying the size of the critical nucleus beyond which unrestricted droplet growth happens. To illustrate the phenomena we devise a minimal model of fermions in a Chern insulating system coupled to a classical Ising field in two spatial dimensions. Using a combination of analytic and numerical methods we conclusively show that topological phases can lead to characteristic quantum surface tension. In this talk I will try to motivate some of these questions, and provide a general overview of quantum condensed matter landscape.

Studying solar flares with the X-ray telescope STIX on Solar Orbiter

Date: 2024-12-05
Speaker: Dr. Alexander Warmuth
Venue: USO Seminar Hall

Abstract

Of the six remote-sensing instruments aboard ESA's Solar Orbiter spacecraft, the Spectrometer/Telescope for Imaging X-rays (STIX) is the one dedicated to the study of solar flares. It performs X-ray imaging spectroscopy in the hard X-ray regime, which provides key physical diagnostics on both the hot thermal plasma as well as on the accelerated energetic electrons. During its operation since launch in 2020, STIX has detected over 56,000 solar flares. I will discuss how the STIX data are used to study energy release and particle acceleration in solar flares. In particular, I will focus on studies that use STIX jointly with other observational assets, such as the other remote-sensing instruments on Solar Orbiter, various instruments on other spacecraft, and in-situ particle detectors.

Unveiling the mechanism behind sign changes in the thermopower and Hall coefficient of strained Sr2RuO4

Date: 2024-12-04
Speaker: Dr. Sudeep K. Ghosh, IIT Kanpur
Venue: Room no: 469 (Main Campus)

Abstract

Sr2RuO4 is a fascinating material in condensed matter physics, celebrated for its unconventional superconductivity and intricate electronic structure. A particularly intriguing aspect is its strain-induced Lifshitz transition, which profoundly influences transport properties. Notable among these effects are the sign changes observed in the thermopower and Hall coefficient under strain, a phenomenon that remains not fully understood. In this talk, I will explore these transport properties using the semiclassical Boltzmann transport formalism, examining both unstrained and strained (uniaxial and c-axis) systems. I will demonstrate that the sign changes are driven by the Van Hove singularity, which emerges as a direct consequence of the Lifshitz transition, offering deeper insights into the electronic structure and transport behavior of Sr2RuO4.

Major ion and trace element geochemistry of the Mahi River

Date: 2024-12-03
Speaker: Dr. Shailja Singh
Venue: Ground Floor Lecture hall

Abstract

River Mahi drains through semi-arid regions of Western India and is the third-major river draining into the Arabian Sea. This work presents an extensive dataset on the major ion and trace element (TE) geochemistry of the Mahi River which forms a part of our continued geochemical investigation on the role of the medium-sized river system in transporting dissolved loads to the Arabian Sea. The major ion data was used to get detailed insights into sources of major ions and their relative contributions by a forward model; seasonal, spatial, and inter-annual variability of these ions, weathering rates, and associated CO2 drawdown of the basin. Likewise, the trace element data was analyzed to identify the role of natural and anthropogenic sources in contributing to TE distribution and understand their spatial and temporal variability. With TEs' obvious link to water quality issues and human health, this work also attempted predictive modeling of pollution indices by Machine Learning models. In this talk, the important results borne out of the work will be discussed.

Introduction to High-Energy Neutrino Astrophysics

Date: 2024-12-02
Speaker: Dr. Bhupal Dev, Washington University, USA
Venue: Room no: 469 (Main Campus)

Abstract

We will provide a pedagogical introduction to High-Energy Neutrino Astrophysics and the emerging field of Multimessenger Neutrino Astronomy. We will discuss how the high-energy neutrinos are produced, propagate and are detected and what they can tell us about the origins of cosmic rays, dark matter, and other fundamental puzzles of the Universe.

Fast Radio Bursts, a recent discovery in the field of Transients

Date: 2024-11-29
Speaker: Shruti Bhatporia
Venue: USO Seminar Hall

Abstract

Fast radio bursts (FRBs) are high-energy transient signals of millisecond duration detected by radio telescopes around the world. The origins of such FRBs are unknown. Therefore multiple theoretical models have been put forward to explain the phenomena. The frequency distribution of energy, duration, and waiting time for solar radio bursts is similar to that of FRBs. There is a correlation between the X-ray and radio luminosity of solar radio bursts, which suggests that the energetic electrons that cause radio emissions and X-ray flares have a common origin. In this talk, I will give an introduction to fast radio bursts and elaborate on ongoing multi-wavelength observation efforts.

Collider fingerprints of freeze-in dark matter

Date: 2024-11-29
Speaker: Dr. Anupam Ghosh, PDF, PRL
Venue: Room no: 469 (Main Campus)

Abstract

We examine a simple dark sector extension where the observed dark matter (DM) abundance arises from a freeze-in process through the decay of heavy vector-like quarks into a scalar dark matter candidate. The detection prospects of such DM are challenging due to the feeble nature of the interactions, but these vector-like quarks can be produced copiously at the LHC, where they decay to Standard Model quarks along with DM. Depending on the decay rate, this scenario is typically probed through long-lived particle or displaced vertex signatures, assuming a radiation-dominated background. An alternative hypothesis suggests that the Universe may have experienced a rapid expansion phase instead of the standard radiation-dominated one during freeze-in. This would significantly alter the dark matter phenomenology, requiring a substantial increase in the interaction rate to match the observed relic density, resulting in the rapid decay of the parent particle. As a result, much of the parameter space for this scenario is beyond the reach of traditional long-lived particle and displaced vertex searches. Due to this non-standard cosmic evolution, existing constraints do not cover the expanded dark matter parameter space. We propose a complementary search strategy to explore this scenario, offering additional limits alongside searches for long-lived particles and displaced vertices. In our search, we investigate the FIMP dark matter model at the LHC using boosted fatjets and significant missing transverse momentum. To improve precision, we include one-loop QCD corrections for LHC production processes and employ a boosted decision tree multivariate analysis, leveraging jet substructure variables to explore a vast parameter space for this minimally extended FIMP dark matter model at the 14 TeV LHC.

TOI-6038 A b: Discovery of a sub-Saturn orbiting a late F-type star in a wide binary system

Date: 2024-11-28
Speaker: Sanjay Baliwal
Venue: Room No. 113/114, Thaltej

Abstract

The discovery of exoplanets has revealed numerous planetary populations with no analogs in the Solar System. Among these, sub-Saturn exoplanets, larger than Neptune but smaller than Saturn and in close orbits around their host stars, represent a particularly intriguing class. Sub-Saturns are often described as failed gas giants, possessing equally massive cores but significantly smaller total masses due to their much smaller accreted envelopes. In this talk, I will discuss our recent discovery of a sub-Saturn TOI-6038 A b using PARAS-2 spectroscopic observations. TOI-6038 A b is a relatively dense sub-Saturn with a mass of approx 79 Earth masses and a size of about 6.4 Earth radii, orbiting a bright, metal-rich late F-type star in a nearly circular orbit with a period of about 5.83 days. The system also contains a wide-orbit binary companion, TOI-6038 B, which is an early K-type star at a projected separation of 3217 AU. Internal structure modeling indicates that about 74% of the planet’s mass is made up of rocky materials forming the core, with the rest consisting of a low-density H/He envelope. TOI-6038 A b lies in the transition zone between the Neptunian ridge and savanna, making it a key system for understanding the formation and evolution of close-in sub-Saturns. While its high density is consistent with planets shaped by high-eccentricity tidal migration, the exact migration pathway remains unclear. The planet’s bright host star makes it a promising candidate for future atmospheric escape and orbital architecture observations, which will help us better understand its overall evolution.

Neutrinos: Dirac or Majorana

Date: 2024-11-26
Speaker: Dr. Bhupal Dev, Washington University, USA
Venue: Room no: 469 (Main Campus)

Abstract

Whether neutrinos are Dirac or Majorana particles is an open question in fundamental physics. Theoretically, it is also possible that neutrinos are pseudo-Dirac, which are fundamentally Majorana fermions, but essentially act like Dirac fermions in most experimental settings, due to extremely small active-sterile mass splitting. Such small values of mass splitting can be accessed via active-sterile oscillations over an astrophysical baseline. We use the recent multi-messenger observations of high-energy neutrino sources to probe hitherto unexplored values of active-sterile mass splitting, which improve the reach of terrestrial experiments by more than a billion.

Understanding the Ocean Conditions during the Neoproterozoic: Depositional Environment, Primary Productivity and Hydrographic Setting of Vindhyan Basin

Date: 2024-11-26
Speaker: Mr. Deependra Singh
Venue: Ground Floor Lecture hall

Abstract

Neoproterozoic Ocean is considered as a profound interval of global environment changes in the geological history. To asses the redox history and primary productivity in the Neoproterozoic ocean is crucial for better understanding of past climate and the changes happened that time. In this talk, I will discuss about utilization of various trace elements and Mo isotopic composition as proxy to understand the paleo environmental conditions of Neoproterozoic upper Vindhyan basin.

PROBA-3 mission

Date: 2024-11-25
Speaker: Dr. Marek Jerzy Stęślicki
Venue: USO Seminar Hall

Abstract

Understanding Solar Eruptions: Ongoing and Future Research Programs at Space Research Centre of Polish Academy of Sciences.

Date: 2024-11-25
Speaker: Dr. Tomasz Maciej Mrozek
Venue: USO Seminar Hall

Abstract

Solar Physics Division, Space Research Centre of the Polish Academy of Sciences aims to observe and interpret solar X-rays. The group performed the first Polish space experiment (54 years ago) resulting in X-ray images obtained using several filters. SPD's increasing heritage led us to participate in the STIX experiment onboard the Solar Orbiter mission. The STIX's data analysis and interpretation is now our main activity. Apart from this, we are involved in CubiXSS experiment (NASA-lead) and MIRORES (all-Polish). During my seminar, I will shortly present the team, our experience, achievements and future ideas that we hope to realize.

Probing the Physics of Radiation and Particles Emitted During Energetically-Rich Solar Flares

Date: 2024-11-21
Speaker: Dr. Arun Kumar Awasthi
Venue: USO Seminar Hall

Abstract

Solar flares are one of the earliest observational signatures of solar eruptions. Although the X-class flares are the largest in intensity class, weaker (micro/nano) flares are more frequently occurring. Therefore, they are not only a suitable candidate for coronal heating, but their investigation may also provide crucial insights into the origin of particle emission from the Sun. By reconciling multi-wavelength observations, the standard flare energy release scheme puts forth the physical mechanism responsible for the radiation and particle emission during flares. However, this scheme is often challenged by the observations, particularly during weak flares that remained less investigated in the past owing to observational limitations. Therefore, it is yet to be understood if the weak flares are just a scaled-down version of large flares in the sense of physical processes. In this context, I will provide an overview of the role of weak flares as unique tracers of pre-eruptive plasma and magnetic field environment from the insights gained from our research investigations. I will also provide an overview of our future plans associating the physics of solar flares with the initiation mechanism of the coronal mass ejections with an emphasis on combining the observations from the ADITYA-L1 and the Solar orbiter missions.

Holocene climate reconstruction from the southern Arabia: A tale of monsoons, humans, and lakes

Date: 2024-11-19
Speaker: Mr. Shah Parth
Venue: Ground Floor Lecture hall

Abstract

The Arabian Desert is considered climatic sensitive zone which is susceptible to changes subtle global atmospheric circulation. The unique geographical location of this region can provide an excellent opportunity to understand the interactions between the monsoons, zonal migrations of the Inter-Tropical Convergence Zone (ITCZ) and regional environmental change. Thus, this project aims to provide the lacking high-resolution information on climate variability in the southern margins of the Arabian Desert through multiproxy approach carried out on a sediment core retrieved from Lake Karif Shawran and paleolake Gayal el Bazal, southern Arabian Desert. The multi-proxy approach includes granulometry analysis, elemental geochemistry, TOC/TIC, ostracod, biomarkers (n-alkanes, Pr/Ph, PAHs, Coprostanol, Stigmastanol and compound specific isotopes). Changes in the lithology and related measured proxies clearly indicate alternating wet and dry periods throughout the last ~4400 years. The wet climatic episodes coincide with globally recognized climate events including the Medieval Climate Anomaly (MCA), and the Roman Warming Period (RWP), whereas the dry intervals occurred during the Little Ice Age (LIA), Late Antique Little Ice Age (LALIA), and the ‘4.2k event’. Overall, we have reconstructed the late Holocene in the southern Arabian desert and discussed the impact of climate on the regional environment and lake system. Moreover, estimating the impact of climate on humans in the region by differentiating climatic signals from anthropogenic signals. The study provides key insights into the main driving forcing behind hydroclimatic changes in the region and sheds light on the role of the ITCZ vis-à-vis monsoonal dynamics. Additionally, it lays the foundation for better understanding long-term seasonal predictions for Southern Arabia.

Active Galactic Nuclei - An Overview

Date: 2024-11-14
Speaker: Priyadarshee P. Dash
Venue: Seminar Room #113 (Thaltej Campus)

Abstract

Active Galactic Nuclei (AGN) are among the most energetic and luminous astronomical sources in the Universe. With bolometric luminosities reaching up to Lbol = 1048 erg s−1 (or 1015 L⊙), the AGNs emit across the entire range of the electromagnetic spectrum. The central source in an AGN is thought to be a supermassive black hole actively accreting nearby matter through an accretion disk, releasing substantial energy in the process. In this talk, I will provide an overview of various components of an AGN that account for its distinctive features across different regions of the electromagnetic spectrum. Emphasis is placed on the X-ray spectrum of the AGN, which offers crucial insights into the energetic processes close to the central engine. Finally, I will discuss the Unified Model of AGNs, which explains how diverse astronomical objects - such as Seyfert galaxies, quasars, radio galaxies - fit under the overarching category of AGN, despite differing in their observational characteristics.

Formation of homologous blowout jets and their large-scale consequences

Date: 2024-11-14
Speaker: Dr. Binal Patel
Venue: USO Seminar Hall

Abstract

Coronal jets are identified as transient coronal-temperature ejections from near the solar surface into the corona. A particular type of coronal jet, known as a blowout jet, has gained significant attention in recognizing the physical mechanism governing the jet-coronal mass ejection (CME) relationship. In this talk, I will discuss the formation of four CMEs originating from homologous blowout jets. All of the blowout jets originated from NOAA Active Region (AR) 11515 on 2012 July 2, within a time interval of 14 hr. All of the CMEs were wide (angular widths between 95–150 deg), and propagated with speeds ranging between 300 and 500 km/s in LASCO coronagraph images. Observations at various EUV wavelengths in Solar Dynamics Observatory/Atmospheric Imaging Assembly images reveal that in all the cases, the source region of the jets lies at the boundary of the leading part of AR 11515 that hosts a small filament before each event. Coronal magnetic field modeling based on nonlinear force-free extrapolations indicates that in each case, the filament is contained inside of a magnetic flux rope that remains constrained by overlying compact loops. The southern footpoint of each filament is rooted in the negative polarity region where the eruption onsets occur. This negative polarity region undergoes continuous flux changes, including emergence and cancellation with opposite polarity in the vicinity of the flux rope, and the EUV images reveal brightening episodes near the filament’s southeastern footpoint before each eruption. Therefore, these flux changes are likely the cause of the subsequent eruptions. These four homologous eruptions originate near adjacent feet of two large-scale loop systems connecting from that positive polarity part of the AR to two remote negative polarity regions, and result in large-scale consequences in the solar corona.

The Mesoarchean Gabbro anorthosite suite: a window to understand the Mesoarchean crustal formation.

Date: 2024-11-12
Speaker: Ms. Mudita Tater
Venue: Ground Floor Lecture hall

Abstract

Gabbro anorthosite rocks preserved in Archean terranes give an important view of early earth geodynamic processes. One such Gabbro anorthositic complex is also reported from the Singhbhum craton. These Mesoarchean rocks preserves the crustal record from Hadean to Archean. In this talk, I will summarize the work done till date on these Mayurbanj Gabbro anorthosite rocks and upbring the current controversies or current research gaps within this area. I will also talk about the potential lunar analogue site. Whether the present gabbro anorthosite complex can be established as potential lunar analogue site.

Implications of Residual modular symmetries on neutrino masses and mixing

Date: 2024-11-11
Speaker: Dr. Monal Kashav, PDF, THEPH
Venue: Room no: 469 (Main Campus)

Abstract

"This talk explores the implications of modular invariance for neutrino mass matrices at the self-dual point τ=i. Assuming both exact self-duality and modular form for the neutrino Yukawa couplings provides some new insights into neutrino mass and mixing patterns. "

Investigation of the source of whistler waves observed near Venus

Date: 2024-11-08
Speaker: Aarti Yadav
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Whistler waves are electromagnetic plasma waves which are frequently observed near Venus. On Venus, atmospheric lightning is considered as a source of whistler wave generation. However, a recent observation made by Parker Solar Probe during its 4th Venus flyby, detected whistler waves in the magnetotail region. After further analysis it was found that the origin of these waves is inconsistent with planetary sources. Investigation of the new source is necessary to add the valuable information about whistler waves, its generation process and the planetary medium through which they are propagating. We will discuss the potential new source which can be responsible for the generation of these waves. The main focus will be the analysis method which will be used in the investigation of the source of whistler wave generation in the magnetotail region of Venus. After that we'll discuss the initial results obtained by using the analysis method.

Ultraviolet Observations of the Martian Upper Atmosphere

Date: 2024-10-25
Speaker: Dr. Krishnaprasad Chirakkil, Research Scientist Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, USA.
Venue: Online Meeting

Abstract

Ultraviolet emissions from planetary atmospheres are valuable for studying the composition and energetics of the upper atmosphere. In this seminar, I will discuss observations from the Emirates Mars Mission (EMM) / Emirates Mars Ultraviolet Spectrometer (EMUS), which have enabled us to study the thermosphere, exosphere, and auroral processes at Mars in unprecedented detail. EMUS is a far ultraviolet (FUV) spectrograph operating in the wavelength range of approximately ~100–170 nm. Its high sensitivity and the unique orbit of EMM allow for synoptic disk imaging and profiling of the tenuous oxygen corona, which is otherwise difficult to observe. The oxygen emission line at 130.4 nm is a prominent emission feature observed both on the dayside and the nightside during discrete auroras. We utilized this emission to construct over 500 oxygen corona profiles, ranging from exobase altitude up to several Martian radii, across all seasons and over two Martian years. Our analysis revealed that the OI 130.4 nm emission is highly correlated with solar irradiance and the Sun–Mars distance, exhibiting short-term variability consistent with the solar rotation period (~27 days) and long-term variability associated with the progression of the solar cycle. Comparison between Mars Years 36 and 37 showed interannual variability, with enhanced emission intensities during MY 37 due to the rise of Solar Cycle 25. These observations indicate a highly variable oxygen corona, which has significant implications for understanding the photochemical escape of atomic oxygen from Mars. Furthermore, our comprehensive study of nightside discrete auroras revealed distinct patterns in auroral occurrence. Aurora activity is higher in regions with open magnetic topology, occurring more frequently near the terminator and predominantly on the dusk side of the night hemisphere. Aurora occurrence exhibits a seasonal dependence, peaking near perihelion and increasing with solar activity. The brightest auroral emissions were detected during space weather events such as coronal mass ejections and stream interaction regions. These findings enhance our understanding of where and when Martian auroras occur, offering insights into the planet's magnetic environment and its interaction with the heliosphere. Overall, EMUS observations provide new insights into the variability of the Martian oxygen corona and auroral phenomena, contributing to our understanding of Mars' atmospheric escape processes and its interaction with the solar wind.

Enhancing Localization of Daksha-GRBs using Coded Mask Imaging Technique

Date: 2024-10-24
Speaker: Mr. Ashish Kumar Mandal
Venue: Seminar Room #113 (Thaltej Campus)

Abstract

Gamma ray bursts (GRBs) are the intense extragalactic gamma ray flashes which last for a few milliseconds to a few hundreds of seconds. The simultaneous detection of both the gravitational wave (GW) and electromagnetic (EM) signals is the only way to probe the origin of short GRBs (flash duration<2s). Hence both sensitivity of GW and EM detectors is essential in addition to all sky coverage of EM detectors. Daksha is a proposed high energy transient mission of India providing full sky coverage with better sensitivity whose primary goal is to detect electromagnetic counterparts of gravitational wave events. In addition to the sensitivity of EM detectors, precise localisation of events is very crucial for their follow up afterglow study in other EM wave bands. The short GRB afterglow study is important since it carries signatures of elements heavier than iron formed from r-process nucleosynthesis of neutrons in the ejecta of BNS merger, also many fundamental physics can be verified from the signatures carried by these events at high redshifts. The proposed Daksha configuration estimates localization based on the ratio of photon counts on detectors at different orientations. In this work we explore the improvement of localization in Daksha if a coded mask is used for either low or medium energy detectors. For this, we have estimated both sensitivity and localization accuracy of Daksha detectors.

Large Blue Spectral Index from a Conformal Limit of a Rotating Complex Scalar

Date: 2024-10-22
Speaker: Dr. Sai Chaitanya Tadepalli, Indiana University, USA
Venue: Room no: 469 (Main Campus)

Abstract

CDM isocurvature power with large blue spectral index can explain the 2-sigma hint in Planck data and recent JWST observation of high redshift galaxies. A well-known method for generating a large blue spectral index for axionic isocurvature perturbations involves a flat direction without a quartic potential term for the axion field's radial partner. In this talk, we discuss how a large blue spectral index can be achieved even with a quartic potential term linked to the Peccei-Quinn symmetry breaking radial partner. We utilize the fact that a large radial direction with a quartic term can naturally induce a “conformal limit”, producing an isocurvature spectral index of 3. Alternatively, this limit can be seen as the angular momentum of the initial conditions slowing the radial field or as a superfluid limit. The large angular momentum necessitates a careful quantization process to establish the vacuum state. We outline the parametric region that aligns with axion dark matter and isocurvature cosmology, and discuss prospects for future detection.

Graphitization for Radiocarbon Dating with AGE3: Development & challenges

Date: 2024-10-22
Speaker: Mr. Ankur Dabhi
Venue: Ground Floor Lecture Hall

Abstract

Radiocarbon dating is a widely used dating technique in earth sciences and archaeology. 1MV Accelerator Mass Spectrometer at PRL has been successfully measuring radiocarbon in variety of natural samples. Graphitization is a crucial step in radiocarbon dating, enabling the transformation of carbonaceous samples into a form suitable for AMS. Graphitization with Automated Graphitisation Equipment(AGE-3) is an innovative approach designed to enhance the efficiency and accuracy of graphitization. In this talk, I will discuss the procedural advancements and optimization of graphitization with AGE3,the challenges and some results showing the quality of graphite produced with AGE-3.

Study of granite genesis through earth analogue: Bridging Earth with Moon and Mars

Date: 2024-10-18
Speaker: Dr. Riya Debacharya Dutta
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The petrogenesis of granite plays a key role in understanding earth’s geological processes, and it offers insight into the history and evolution of other terrestrial planets as well. The mineral assemblage, textural association record the information about depth, temperature, composition of parental melt from which it crystallizes. Although less common, the presence of granite or granite like components in Moon and Mars can shed light on the planetary differentiation and prolonged magmatic processes. In this seminar, I will discuss the fundamentals of granite formation through petro-geochemical study of granites from Mount Abu and surrounding areas and will try to correlate the magmatic processes for genesis of granitic components in Moon and Mars.

Stellar evolution in star clusters

Date: 2024-10-17
Speaker: Dr. Ranjan Kumar
Venue: Seminar Room #113 (Thaltej Campus)

Abstract

Star clusters are ideal places to explore the formation and evolution of stellar systems. They host stars of almost all the evolutionary phases. Mostly, young and massive stars dominate the open clusters, whereas the globular cluster traces the evolutionary sequence of low-mass stars. They also contain exotic stellar populations (e.g., blue straggler stars, blue hook stars, AGB-manque stars, low mass He white dwarf, and catalysis variables, etc.), which are byproducts of dense stellar environments and/or binary stellar systems in the cluster. The ultraviolet (UV) emission in star clusters is mostly dominated by the young (massive), exotic, and evolved stars, which are important to studying the formation and evolution of a star cluster. I will present the first comprehensive ultraviolet (UV) source catalogue (UVIT DR1) of UV photometry in various FUV (1300−1800 A) and NUV (2000−3000 A) filters of the UltraViolet Imaging Telescope (UVIT) onboard AstroSat. UVIT DR1 includes a total of 239,520 unique UV-bright sources, of which 70,488 sources have FUV magnitudes, and 211,410 have NUV magnitudes covering a sky area of ~ 58 sq. deg. I will showcase the results of a newly discovered hot post-AGB star in a sparse Galactic globular cluster, E3 (ESO 37-1), using UVIT observations. I will discuss its binarity, chemical abundance and evolutionary status utilizing observed/archival datasets of the UVIT/AstroSat, Gaia DR3, and high-resolution spectra. In this talk, I will also discuss the preliminary results of the study of blue straggler stars in selected star clusters using photometric and spectroscopic observations of the 2.5m telescope, Mt. Abu.

Spacewire Protocol for Planetary Instrumentation

Date: 2024-10-11
Speaker: Sanjeev Kumar Mishra
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Backend electronics is one of the critical subsystem of and instrumentation for planetary applications. Within the backend electronics, data handling and communication between the instrument and the spacecraft is crucial. There are many ways in which it is realized, each depending upon their unique requirents. Space agencies worldwide have different data handling and communication protocols for different missions most of which are not standardized. Spacewire is one of the first such attempt to standardize the communication protocol. In this talk, I will be providing an overview of this protocol, design and implementation plans.

Gravitational wave and multi-messenger signals from compact binary mergers

Date: 2024-10-10
Speaker: Prof. Kunal Mooley
Venue: Seminar Room #113 (Thaltej Campus)

Abstract

More than 150 high-significance gravitational wave (GW) sources, primarily binary black hole mergers, have been detected by ground-based GW observatories to date. The joint GW and EM detections of the binary neutron star merger GW170817 yielded a scientific bonanza in fields as wide-ranging as gravitational physics, nucleosynthesis, neutron star equation of state, relativistic explosions and jets, and cosmology. The EM counterpart of GW170817 gave insight into the mass, speed and composition of the slow-moving merger ejecta through the rapidly-evolving kilonova emission (from r-process nucleosynthesis), while the long-lasting afterglow probed the energetics and morphology of the relativistic ejecta (jet and cocoon). It also provided an unambiguous link between neutron star mergers and short gamma-ray bursts, and facilitated a precise measurement of the Hubble's constant. I will discuss the astrophysics and fundamental physics learned from GW170817 and what could be learned from future GW events: like NS-NS and NS-BH mergers. I will also describe the searches for systems like NS-BH and high-mass-ratio systems in the Galactic Center that will be important for space-based detectors like LISA.

Molecular Characterization of Brown Carbon Using Fluorescence Spectroscopy

Date: 2024-10-08
Speaker: Dr. Devprasad M.
Venue: Ground Floor Lecture Hall

Abstract

On a global scale, aerosols cool the atmosphere by scattering incoming solar radiation. However, absorbing aerosols such as black carbon (BC), brown carbon (BrC), and dust can significantly alter this effect on a regional scale. Radiative forcing (RF) estimates for BC and dust are relatively straightforward due to their simpler structures and primary emissions. In contrast, brown carbon is more complex, with a wide variety of forms and both primary and secondary sources. A detailed treatment of BrC is often lacking in climate models. Observations suggest that the RF due to BrC can be 20–40% of the RF due to BC, with even higher values reported for biomass-burning-dominated regions. A significant spatial and temporal variations have been observed in the RF of BrC, necessitating their characterization on molecular level. Various methods are used for this purpose. Among these, fluorescence spectroscopy stands out for its high sensitivity, repeatability, minimal sample preparation, non-destructive nature, and ease of operation. In this talk, I will discuss the basics of brown carbon and how fluorescence spectroscopy can be used to identify its dominant species.

Quantum aspects of the conformal sector of gravity and torsion in 4D

Date: 2024-10-07
Speaker: Mr. Abbas Tinwala
Venue: Online---https://imeet.vconsol.com/viewer/5845393127?be_auth=NTIzNzU2

Abstract

"Classical conformal invariance is expected to hold quite well at energies MSM ≪ E≪ MP. so that the Standard Model (SM) particle masses, MSM, may be neglected while at the same time, quantum gravity can be assumed to contain only massless spin-2 particles. Coincidentally, consistent theory of propagating torsion coupled to SM particles is possible only for massless fermions which can be realized if E Mfer ≫ for the mass Mfer of heaviest fermions. In addition to fermions if torsion is coupled to scalar fields then the theory of propagating torsion is not possible due to unitarity violations found at the two-loop order. In this regard, recently proposed theories of composite Higgs particles which indicate that the Higgs field manifests as fermionic condensate could be a sign of relief for the torsion theory since at energies higher than the electroweak scale one ends up only with fermions (and bosons with non-zero spin). Even in this scenario, there may still be an obstacle to realizing the theory of propagating torsion since we must deal with the conformal sector of gravity. In this talk, I will show that the anomaly-induced effective action including torsion [3], consists of a scalar field representing the conformal sector of gravity coupled to torsion potentially causing similar unitary violations. A calculation of one loop and/or two loop divergences in the theory of conformal factor and torsion and a subsequent analysis of the beta functions become necessary to clarify the status of torsion as a propagating field."

Flare Response in the Photosphere and Chromosphere: A Multi-line Spectropolarimetric Study

Date: 2024-10-04
Speaker: Dr. Rahul Yadav
Venue: USO Seminar Hall

Abstract

Solar flares, driven by magnetic reconnection in the corona, rapidly release immense energy into the solar atmosphere. Observations have shown that a flare influences different layers of the solar atmosphere almost simultaneously. However, it is still unclear how a flare impacts the lower solar atmosphere. Multi-line spectropolarimetric observations, covering different layers, are necessary to present a comprehensive view of flares. In this talk, I will explore the lower atmospheric response to flares using multi-line spectropolarimetric observations. I will demonstrate how these observations, combined with state-of-the-art multi-line inversion code, can be used to construct a stratification of physical parameters such as temperature, magnetic field vector, line-of-sight velocity, and macroturbulent velocity within a flaring atmosphere. The resulting semi-empirical model will be directly compared with theoretical flare models. Additionally, I will present recent findings from the 4-meter Daniel K. Inouye Solar Telescope, focusing on the rotation of pores associated with flares on a significantly smaller scale.

Understanding the Space Weather Impact of Coronal Mass Ejections Utilising Observations and Modelling

Date: 2024-09-30
Speaker: Dr. Ranadeep Sarkar
Venue: USO Seminar Hall

Abstract

The most challenging problem in space weather research is to predict the intensity of geomagnetic storms at Earth. During these storms modern infrastructure in space and on ground can experience significant hazards, such as disruptions of communication and power lines, and malfunctions or even a failure of satellites in orbit. The storms occur when an Earth-directed interplanetary coronal mass ejection (ICME) and/or their frontal sheath carries a strong southward interplanetary magnetic field (IMF) Bz. Therefore, the prediction of Bz inside both the ICME and sheath regions, is the prime requirement to forecast the severity of geomagnetic storms. Since the magnetic field of solar eruptions cannot reliably be measured via remote means, and direct continuous measurements of the Earth impacting solar transients are routinely available only very close to our planet, modelling of CME magnetic properties is paramount. In this talk, I will present a space weather modelling framework using both analytical and global MHD approaches that could prove to be an operation space weather forecasting tool to predict the geo-effectiveness of CMEs. This talk will also showcase the utilisation of multi-wavelength remote-sensing observations as well as multi-spacecraft in-situ observations at different heliocentric distances to constrain the space weather forecasting models. I will further discuss how data from India's space-based solar observatory, Aditya L1, and ISRO’s upcoming mission to Venus will play a crucial role in enhancing our understanding on the initiation and space-weather effects of CMEs.

Understanding the Space Weather Impact of Coronal Mass Ejections Utilising Observations and Modelling

Date: 2024-09-30
Speaker: Dr. Ranadeep Sarkar, Postdoctoral Fellow, Space Physics Department, University of Helsinki
Venue: USO Seminar Hall

Abstract

The most challenging problem in space weather research is to predict the intensity of geomagnetic storms at Earth. During these storms modern infrastructure in space and on ground can experience significant hazards, such as disruptions of communication and power lines, and malfunctions or even a failure of satellites in orbit. The storms occur when an Earth-directed interplanetary coronal mass ejection (ICME) and/or their frontal sheath carries a strong southward interplanetary magnetic field (IMF) Bz. Therefore, the prediction of Bz inside both the ICME and sheath regions, is the prime requirement to forecast the severity of geomagnetic storms. Since the magnetic field of solar eruptions cannot reliably be measured via remote means, and direct continuous measurements of the Earth impacting solar transients are routinely available only very close to our planet, modelling of CME magnetic properties is paramount. In this talk, I will present a space weather modelling framework using both analytical and global MHD approaches that could prove to be an operation space weather forecasting tool to predict the geo-effectiveness of CMEs. This talk will also showcase the utilisation of multi-wavelength remote-sensing observations as well as multi-spacecraft in-situ observations at different heliocentric distances to constrain the space weather forecasting models. I will further discuss how data from India's space-based solar observatory, Aditya L1, and ISRO’s upcoming mission to enus will play a crucial role in enhancing our understanding on the initiation and space-weather effects of CMEs.

Exploring the Spectral and Physical characteristics of Lunar Pyroclastic Deposits

Date: 2024-09-27
Speaker: Dibyendu Misra
Venue: Online

Abstract

Lunar Pyroclastic Deposits (LPDs) play a key role in understanding the explosive volcanic activity on the Moon. These deposits consist of partially crystallized volcanic glasses, which retain essential information about the primary lunar mantle composition. However, the remote identification of these volcanic glasses is challenging, due to their similar spectral characteristics to common lunar minerals in the visible to near-infrared wavelength range. In this seminar, I will introduce a novel approach for detecting and characterizing LPDs, utilizing the Chandrayaan-1 Moon Mineralogy Mapper data. Additionally, I will discuss insights into the surface behavior of these deposits through multispectral imaging polarimetric data obtained from Mount Abu. The results derived using the newly proposed method will be discussed by considering a few typical case studies of known pyroclastic deposits.

Resonant and Secular Evolution of Three Body Systems – With Applications to Planetary Systems and Gravitational Wave Sources

Date: 2024-09-26
Speaker: Dr. Hareesh Gautham Bhaskar
Venue: Seminar Room #113 (Thaltej Campus)

Abstract

The three-body problem describes the motion of three objects under the influence of their mutual gravity. It is one of the oldest problems in astrophysics. No closed form analytical solution is possible to the general three body problem due to its chaotic nature. Despite its rich history, the three-body problem remains an active area of research. Recent advancements in the field are motivated by new discoveries pertaining to exoplanets and blackholes. In this work we focus on resonant and secular interactions in three body systems, with a goal to understand how these interactions influence the long-term stability and evolution of three body systems. We apply our theoretical investigations of these physical processes to a wide range of observed systems. We find that secular and resonant perturbations can significantly affect the stability limit of mutually inclined planets. Planets in retrograde configurations are much more stable than prograde configurations, with secular perturbations significantly destabilizing the system when 200 < Imut < 1600. In addition, we find that secular three body dynamics can also help us constraint the inclination of the hypothetical Planet-9 in the outer solar system, and explain the observed retrograde stellar obliquities of hot Jupiters. We also propose a novel pathway through which compact binaries could merge due to eccentricity excitation caused by resonant interactions induced by a massive coplanar companion. Specifically, a compact binary migrating in an AGN disk could be captured in a precession-induced resonance, when the apsidial and nodal precession rates of the binary are commensurable to the orbital period around the supermassive black hole. Eccentricity is excited when the binary sweeps through the resonance which happens only when it migrates on a timescale 10-100 times the libration timescale of the resonance. The eccentricity excitation of the binary can reduce the merger timescale by a factor up to 103 -105.

Josephson diode effect in a quantum dot junction

Date: 2024-09-24
Speaker: Dr. Debika Debnath
Venue: Room no: 469 (Main Campus)

Abstract

I will discuss the Josephson diode effect (JDE) in a quantum dot (QD)-based Josephson junction (JJ) in the presence of an external magnetic field and Rashba spin-orbit interaction (RSOI). To achieve the diode effect in the JJ, we break the time-reversal symmetry through the Zeeman field, and the inversion symmetry is broken by RSOI. We calculate the Josephson current using the Keldysh nonequilibrium Green’s function technique. Our QD with RSOI induces JDE in the heterojunction with a large rectification coefficient (RC) that can be tuned to be as high as 70% by an external gate potential, indicating a giant JDE in our QD junction. Interestingly, we find that the sign and magnitude of the RC are highly controllable by the magnetic field and RSOI. We also investigate the role of electron-electron correlation to the Josephson diode by incorporating an interacting QD as the intermediate tunnelling medium. Our proposed QD–based Josephson diode (JD) has the potential to be an efficient superconducting device component.

Riverine carbon and nitrogen biogeochemistry in critical zone sites in the western India

Date: 2024-09-24
Speaker: Mrs. Sangeeta Verma
Venue: Ground Floor Lecture Hall

Abstract

पश्चिमी भारत में महत्वपूर्ण क्षेत्र स्थलों में नदी कार्बन और नाइट्रोजन जैव-भू-रसायन

Temperature Profiles and Radiative Transfer Modeling of Protoplanetary Disks

Date: 2024-09-20
Speaker: Soumik Kar
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

A protoplanetary disk is a rotating circumstellar disk composed of dense gas and dust around a recently formed young star. Understanding its evolution is essential to understanding the planet's formation. Volatiles, encompassing diverse compounds such as water, carbon dioxide, and complex organic molecules, significantly impact the composition and characteristics of growing planetary bodies. First, we will discuss the disks' basic properties from observations and numerical models. It will help us understand the complex dynamics that shape the overall structure of protoplanetary disks and influence the spatial distribution of volatiles. Then, we will discuss these disks' radial and vertical temperature profiles, probing the thermal conditions that drive volatile transport and chemical reactions. Finally, we will discuss the radiative transfer code, which calculates the disk temperature using the Monte Carlo technique and discuss the first results.

Contact Binaries: A Detailed Analysis Through Photometric and Spectroscopic Data

Date: 2024-09-19
Speaker: Dr Alaxender Panchal
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Eclipsing binaries (EBs) are essential for understanding stellar evolution, providing direct measurements of stellar masses, radii, and luminosities. Among these, W UMa-type systems, also known as contact binaries, are particularly important because the stars share a common envelope, leading to complex energy exchanges. W Uma-type systems are important as they give information about component interactions, mass-trasfer between components, period evolution, extra bodies around inner binary etc. In this talk, I will present a long-term photometric and spectroscopic analysis of four W UMa-type systems. This study combines light curves with spectroscopic data, revealing details about their orbital parameters, period changes, and evolution. The findings shed light on the internal dynamics of contact binaries, offering valuable insights into stellar interaction and evolution. I will discuss the methods used, the findings, and their significance in the broader context of contact binaries.

Quasiperiodic potential induced corner states in a quadrupolar insulator: A paradigm for higher-order topology

Date: 2024-09-18
Speaker: Prof. Saurabh Basu
Venue: Room no: 469 (Main Campus)

Abstract

The topological and localization properties of a quadrupolar insulator represented by the celebrated Benalcazar-Bernevig-Hughes model is studied in presence of a quasiperiodic disorder. While disorder is expected to disturb the existence of topological order in a system, we observe that a disorder driven topological phase emerges where the original (clean) system demonstrates trivial behavior. This phenomena is confirmed by the re-emergence of the zero energy states together with the non-trivial values of the quadrupole moment. Moreover, the distribution of the excess electronic charge shows a pattern that clearly corresponds to the bulk quadrupole topology. To elaborate upon the localization properties of the mid-band states, we compute the inverse participation and normalized participation ratios. It is observed that the in-gap states become critical (multifractal) at the point that discerns a transition from a topological localized to a trivial localized phase. Finally, we carry out a similar investigation to ascertain the effect of the quasiperiodic disorder on the quadrupolar insulator when the model exhibits topological properties in the absence of disorder. Again, we note a multifractal behavior of the eigenstates in the vicinity of the transition.

Introduction to Artificial Intelligence

Date: 2024-09-13
Speaker: Dr Y B Acharya
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Artificial Intelligence has grown to be very popular in today’s world. It is the simulation of natural intelligence in machines that are programmed to learn and mimic the actions of humans. These machines are able to learn with experience and perform human-like tasks. As technologies such as AI continue to grow, they will have a great impact on our quality of life. It’s but natural that everyone today wants to connect with AI technology somehow, may it be as an end-user or pursuing a career in Artificial Intelligence.

Unraveling the mysteries of Harappan Ernestite: A Geochemical prospective

Date: 2024-09-10
Speaker: Dr. Milan Mahala
Venue: Ground Floor Lecture Hall

Abstract

The Harappan (Indus Valley) civilization, one of the most sophisticated Bronze Age civilizations, survived for over two millennia (5300-2600 yrs BP) in the alluvial plains of the northwestern Indian subcontinent. The Harappan Gujarat was the center of bead manufacturing activities and inter-regional trade networks. The Harappans, known as master crafters and traders of their period, manufactured beads of agate, carnelian, jasper, terracotta, etc., for ornaments and trading purposes. Besides thousands of beads discovered, numerous stone drill bits have also been found from many Harappan sites. These drill bits are believed to have been ground out from certain hard stones, which have been named Ernestites. The origin of Ernestite remains an enigma because it does not resemble any natural rock. If produced artificially, what raw materials were used, and what process was followed in their making? Since deciphering the origin of Ernestite is essential for understanding the manufacturing abilities of these Bronze Age people, we undertook a detailed petrographic, geochemical, and isotopic study of the Ernestites from multiple sites in Gujarat. In this seminar, I shall discuss our findings.

Pseudogap in

Date: 2024-09-05
Speaker: Dr. Jalaja Pandya
Venue: Room no: 469 (Main Campus)

Abstract

Gor'kov and Teitel'baum formulated a phenomenological model for the number of charge carriers, derived from the Hall effect data of La2-xSrxCuO4. The activation energy obtained from this model agreed well with the pseudogap signatures observed in the angle resolved photoemission spectroscopy. Recently, Hall eﬀect measurements are done on Lanthanum doped Strontium Iridate

Efficient Quantum Field Theories for Quantum Computers

Date: 2024-09-03
Speaker: Dr. Debashis Banerjee
Venue: Room no: 469 (Main Campus)

Abstract

"Computing methods on classical computers have dominated the discovery frontline from fundamental physics for several decades now. It is however becoming clear that at least in physics, there are several computational avenues (such as finite density and real-time dynamics) where development can be accelerated via quantum computers. At the same time, improving classical computing techniques using clever analytical insights is essential to provide further inputs to the quantum computing frontier. In this talk, we will discuss the broad ideas behind the novel constructions and selected applications illustrating results for realistic systems in condensed matter and particle physics. Such scenarios are expected to be realized in quantum hardware in the recent future."

Advances in integrating petrochronological and geodynamic models of high-grade metamorphic systems

Date: 2024-09-03
Speaker: Prof. Chris Clark
Venue: Ground Floor Lecture Hall

Abstract

The field of metamorphic petrology has undergone several evolutions beginning with the recognition that certain groupings of minerals reflect thermobaric conditions (index minerals and the facies concept of Eskola). This was followed by the realisation that these same minerals partition elements in a systematic way allowing temperatures and pressures to be quantified (classical thermobarometry) and that whole systems can be mapped in thermodynamic space to generate phase diagrams that capture the evolution of a rock (the pseudosection approach of Holland and Powell in the late 80’s early 90’s). These evolutions have progressed in lock step with the evolution of analytical capabilities that facilitate the collection of chemical (electron microprobes) and isotopic (SIMS and laser ablation mass spectrometry) information from mineral grains that enable the pressure-temperature-time (P–T–t) histories of rocks to be constrained (the field of “Petrochronology” pioneered by researchers such as Daniela Rubatto and Brad Hacker in the early 2000’s). Despite these advances we are still faced by the challenge that the rocks we collect and analyse provide only a snapshot of the journey a single sample takes through an orogenic (mountain building) cycle. A potential path to address this issue is the application of diffusion geospeedometry where the zoning profiles of different mineral can be used to construct a detailed temperature–time history for rocks – as always, a key mineral in this endeavour is garnet. Diffusion chronometry coupled with thermochronometers and 4+ cation thermometers allow more detail on P–T-t paths to be constrained. However, there now exists a dichotomy in the results produced by each approach wherein diffusion based geospeedometry studies generally yield timescales that are orders of magnitude faster that the classical U–Pb geochronological investigations. Begging the question how much of an orogenic evolution are we capturing and are orogenic events long and slow or constructed through a series of pulses? In this talk I will present progress towards the integration of phase diagram tools, diffusion processes, geochronological and petrological datasets with geodynamic models to constrain the evolution of lower crustal rocks during orogenic cycles. This approach, in our opinion, is the obvious next evolution in metamorphic petrology and is being enabled by the concomitant advances in both open-source geodynamic codes, in this case Underworld, and increasing computational power (both at the desktop and supercomputer level). These developments enable individual researchers to develop and test multiple scenarios to see what is plausible based on real geological data and the physics of rock systems at their desk rather than waiting for access to scarce resources such as access to national supercomputer facilities

Noble gases & Nitrogen isotopes: Results from Noble gas mass spectrometer lab

Date: 2024-08-30
Speaker: Ramakant R. Mahajan
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Results from noble gas mass spectrometry lab. will be discussed. Isotopes of noble gases and nitrogen in meteorites provide important information about the formation and evolution of the solar system and beyond.

(1) Chandrayaan-3 APXS elemental abundance measurements: Confirmation of Lunar Magma Ocean hypothesis and ground truth for future remote sensing observations in the southern polar highland region (2) Multiple sources of water in impact glasses from Change-5 lunar soil

Date: 2024-08-23
Speaker: Prof Debabrata Banerjee
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The presentation will discuss OH and molecular H2O related to solar wind and other multiple sources preserved in impact glasses from Chang’e-5 (CE5) lunar soil based on observations of reflectance infrared spectroscopy and nanoscale secondary ion mass spectrometry analyses.

"Non-equilibrium (hot) electron relaxation: Review of the ultrafast phenomena in metals and superconductors. "

Date: 2024-08-22
Speaker: Prof. Navinder Singh
Venue: Room no: 469 (Main Campus)

Abstract

"This field effectively originated when Kaganov, Lifshitz and Tantarov in 1957 put forward their famous Two-Temperature Model (TTM) of non-equilibrium electron relaxation in metals. During the ensuing decades much advance happened due to the advent of femtosecond lasers. In this talk, a chronological review of the field will be presented in which relaxation of hot (non-equilibrium) electrons in semiconductors and superconductors will be discussed. Some works done in PRL in this field will be reviewed. Recent advancement of photo-induced superconductivity will also be discussed."

NLP corrections for H+ jet production

Date: 2024-08-21
Speaker: Dr. Sourav Pal, PDF
Venue: Room no: 469 (Main Campus)

Abstract

Precise experimental data from the Large Hadron Collider and the lack of any persuasive new physics signature demand improvement in the understanding of the Standard Model.The scattering cross-sections are plagued with Leading power (LP) and next-to-leading power (NLP) logarithms. Resummation of LP logarithms has a long history of almost three decades and their resummation methods are well known in the present literature. However, precise prediction also requires the resummation of NLP logarithms, as they have a sizeable numerical impact in the cross-section calculation. These NLP logarithms for colour singlet processes are well known in the literature, however, there is a scarcity of results when final state colour particles are involved in the scattering process. In the talk, I will discuss a new method of calculating the NLP logarithms where final state colour particles are involved and will show its application for Higgs+ jet production.

THE MARINE BIOGEOCHEMICAL CYCLE OF SILICON: INSIGHTS FROM SILICON STABLE ISOTOPES

Date: 2024-08-20
Speaker: Mr. Mahesh Gaddam
Venue: Ground Floor Lecture hall

Abstract

Silicon (Si) is the second most abundant element in the Earth’s crust and is an important nutrient in the ocean. The global Si cycle plays a critical role in regulating primary productivity and carbon cycling on the continents and in the oceans. Silicon has a complex biogeochemical cycle, interacting with other globally important elemental cycles (e.g Carbon and Nitrogen). Dissolved silicon (DSi) and its isotopes (δ30SiDSi) are powerful tool for understanding biogeochemical and ocean processes. In this talk, an outline of Si cycle, along with the measurement methods and application of Si isotope composition in seawater will be discussed.

Study of Martian atmosphere over Hellas and Argyre regions

Date: 2024-08-16
Speaker: Ms. Gayatri Sharma
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

It is known that the Mars consist major gas CO2. The average surface temperature of Mars is about 220 K. The mean surface pressure of Mars is about 6 mbar. Recently, Emirates Mars Infrared Spectrometer(EMIRS) onboard Emirates Mars Mission(EMM) measured surface temperatures at all latitudes and longitudes during spring, summer, autumn and winter seasons. We have analyzed these data and preliminary results over Hellas (42.4°S, 70.5°E) and Argyre (49.75°S, 316°E) regions will be presented in this seminar. In these craters the average surface temperature ~300 K and~160 K are observed during summer and winter respectively. Thus, the temperature values plummet by ~140 K during winter of these basins. It is also found that southern hemisphere's summer is warmest than the northern hemisphere's summer, because Mars is closest to the sun in Southernhemisphere's summer.

Implications of decaying neutrino state in the Bi-magic baseline

Date: 2024-08-16
Speaker: Dr. Supriya Pan, PDF
Venue: Room no: 469 (Main Campus)

Abstract

"The neutrino oscillations have established that there are massive neutrino mass states. The well-understood framework of standard three-flavor neutrino oscillation gives us the scope to look for signatures of new physics beyond the Standard Model. One such scenario is when heavier neutrino states decay into lighter ones, first proposed to describe the zenith-angle dependence in atmospheric-neutrino data at Super-Kamiokande. The baseline of 2540 km has a special feature where the sensitivity to mass hierarchy is very high at probability maxima. In our work, we study how the presence of decay of the heaviest neutrino state will impact the sensitivity to mass-hierarchy and the octant of angle theta23 using the proposed setup of Portvino to ORCA (P2O) experiment at a baseline of 2588 km."

Paleo-pCO2 Reconstructions in the Equatorial Indian Ocean using Boron Isotopic Records of Planktonic Foraminifers

Date: 2024-08-13
Speaker: Dr. Sanjit Kumar Jena
Venue: Ground Floor Lecture hall

Abstract

Carbon dioxide (CO2) constitutes around 80% of the global greenhouse gases in the present atmosphere significantly contributing to global warming and its major climatic consequences such as the melting of ice sheets, sea level rise, ocean acidification and extreme weather events. The global ocean with its substantial storage and exchangeability plays a crucial role in regulating the widespread distribution of atmospheric pCO2, thereby influencing regional and global climatic changes. Reconstruction of past oceanic CO2 is essential to understand the temporal evolution of the climate, helping predict its future trends. Boron isotopic records in planktonic foraminifers offer a key method to reconstruct past oceanic CO2 records. However, precise measurement of boron isotopes has remained a major challenge, especially from mass limited foraminifera samples subject to contamination and isotopic mass fractionation issues. This talk will highlight the potential implications of paleo-pCO2 reconstructions in the Equatorial Indian Ocean to the global paleoclimatic research, and glimpses of the methodological advancements in extraction and precise measurement of boron isotopes in planktonic foraminifera samples.

1D Photochemical Model for Venusian Ionosphere

Date: 2024-08-09
Speaker: Satyandra M Sharma
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The dayside Venusian ionosphere is primarily formed due to photoionization and photoelectron impact ionization of the neutral atmosphere by Solar EUV (15-100 nm) and soft X-rays (1-15 nm) radiations. These processes result in the formation of the V2 (~140km) and V1(~125km) layers in the ionosphere. Additionally, a sporadic layer, V0(~113km), observed below the V1 layer, is suspected to be of photochemical origin, though its exact source remains unidentified. We have developed a photochemical model of the dayside Venusian ionosphere, which has been validated against the electron density profile observations from the Venus Radio Science (VeRa) experiment onboard the Venus Express (VEX). In this seminar, I will discuss about the modeling of the Venus ionosphere.

Insights into High-Resolution Time-of-Flight Aerosol Mass Spectrometry (HR-ToF-AMS): Principles, Components, and Applications

Date: 2024-08-06
Speaker: Mr. Rohit Meena
Venue: Ground Floor Lecture hall

Abstract

High-Resolution Time-of-Flight Aerosol Mass Spectrometry (HR-ToF-AMS) represents a significant advancement in atmospheric chemistry and aerosol science. This technology combines high-resolution mass spectrometry with time-of-flight to measure real-time, non-refractory, size-resolved particulate chemical composition and mass. It facilitates a deeper understanding of aerosol dynamics, source apportionment, and their impacts on air quality and climate. In this talk, I will cover the fundamentals of HR-ToF-AMS, its key components, and their functions and its application.

Chandrayaan-3 and Changing Perspectives of the Moon

Date: 2024-08-02
Speaker: Dr. K. Durga Prasad
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The glorious landing of Chandrayaan-3 at a high latitude location on the Moon was definitely a mesmerising moment for all Indians, particularly for those working for the mission for more than a decade. In addition to providing the first-ever measurements of a never-explored territory, the mission has provided an entirely new perspective of the Moon with its in-situ measurements. ChaSTE is an experiment onboard Chandrayaan-3 lander aimed at investigating the thermophysics at the landing site. After successful landing of Vikram at Shiv Shakti point, ChaSTE probe was deployed and successfully penetrated into the lunar soil to provide the first-ever in-situ thermal measurements at a lunar high latitude location. An insight into lunar thermophysics, experimental challenges, surprises and mission experiences will be discussed.

Assembly-Integration-Testing of ProtoPol, its on-sky commissioning, and subsequent status of its data reduction pipeline

Date: 2024-08-01
Speaker: Arijit Maiti
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

ProtoPol is a medium-resolution echelle spectro-polarimeter initially conceived as the prototype instrument of the currently under development M-FOSC-EP (Mt. Abu Faint Object Spectrograph and Camera-Echelle Polarimeter) instrument – a two-channel multimode instrument which is currently being designed for PRL 2.5m telescope at Mt. Abu. Though ProtoPol was initially conceived to evaluate the development methodology of M-FOSC-EP using commercially available off-the-shelf components, it was later elevated to the level of a full-fledged back-end instrument for PRL telescopes. ProtoPol was designed on the concept of echelle and cross-disperser gratings to record the cross-dispersed spectra in the wavelength range from 390 to 940 nm with a resolution in the range of 7000-8000. ProtoPol has been successfully developed and commissioned on PRL 1.2m and 2.5m telescopes since December 2023, and a variety of observations are being carried out for instrument characterization and scientific purposes. In this talk, I shall discuss the features and properties of ProtoPol, the assembly-integration-testing of the instrument in the laboratory, and its subsequent commissioning on PRL telescopes for on-sky characterization and science observations. I will also talk about the current status of the data reduction pipeline being developed for ProtoPol.

Beyond standard hydrodynamics: “maximum-entropy” theory and the dynamics of critical fluctuations

Date: 2024-08-01
Speaker: Dr. Chandrodoy Chattopadhyay
Venue: Room no: 469 (Main Campus)

Abstract

I will present formulation of ‘maximum-entropy hydrodynamics’, a far-off-equilibrium macroscopic theory that effectively describes both free-streaming and near-equilibrium regimes of the quark-gluon plasma formed in heavy-ion collisions. Unlike standard hydrodynamic theories this formulation incorporates contributions to all orders in shear and bulk inverse Reynolds numbers, allowing it to handle large dissipative fluxes. By considering flow profiles relevant for nuclear collisions at high energies, I will demonstrate that ‘maximum-entropy hydrodynamics’ provides excellent agreement with underlying kinetic theory throughout the fluid’s evolution, especially in out-of-equilibrium regimes where traditional hydrodynamics becomes inapplicable. I will then present formulation of stochastic fluid dynamics to model the evolution of critical fluctuations in a system that is close to a critical point. I will demonstrate that correlation functions of the order parameter exhibit dynamical scaling behavior which is sensitive to the correlation length and shear viscosity of the fluid. I will also show that non-linear interactions between shear modes constrain the minimum value of a fluid’s shear viscosity.

Heavy-ion collisions and hydrodynamics

Date: 2024-07-31
Speaker: Dr. Chandrodoy Chattopadhyay
Venue: Room no: 469 (Main Campus)

Abstract

Ocean Alkalinity Enhancement: A redemption?

Date: 2024-07-30
Speaker: Ms. Shreya Mehta
Venue: Ground Floor Lecture Hall

Abstract

The increased global emissions of greenhouse gases due to anthropogenic activities have led to an increase in climate warming, with present-day mean atmospheric temperature reaching 1.1°C above the preindustrial level. The alarming increase in greenhouse gas emissions has motivated the discussion of climate change and the need to limit the emissions so as to limit the warming below 1.5°C or 2.0°C by the year 2100. To combat this and limit the warming below 1.5°C or 2.0°C by the year 2100, along with reducing CO2 emissions, Negative Emission Techniques (NETs) or Carbon Dioxide Removal (CDR) methods are required. Ocean Alkalinity Enhancement (OAE) is one of the NETs, but uncertainties surround the feasibility and consequences of implementing OAE on a global scale. To address this, we conducted mesocosm experiments in the coastal waters of the Arabian Sea. In this talk, I shall be discussing some of the preliminary findings from these experiments.

FiberPol-6D- Spectropolarimetric Integral Field mode for the SAAO 1.9 m Telescope using fibers

Date: 2024-07-29
Speaker: Dr Siddharth Maharana
Venue: Seminar Room # 113/114 (Thaltej campus)

Abstract

Most optical spectropolarimeters built to date operate as long-slit or point-source instruments; they are inefficient for observations of extended objects such as galaxies and nebulae. 2D spectropolarimetry technique development is a major challenge in astronomical instrumentation. At the South African Astronomical Observatory (SAAO) FiberLab, we are developing a spectropolarimetry capable Integral Field front-end called FiberPol(-6D) for the existing SpUpNIC spectrograph on the SAAO 1.9 m telescope. SpUpNIC is a general purpose 2 arc-minute long-slit spectrograph with a grating suite covering the wavelength range from 350 to 1000 nm. FiberPol generates 6D observational data: x-y spatial dimensions, wavelength, and the three linear Stokes parameters I, q and u. Using a rotating half-wave plate and a Wollaston prism, FiberPol executes two-channel polarimetry, and each channel is fed to an array of 14 fibers, corresponding to a field of view of 10×20 arcseconds^2 sampled with 2.9 arcsecond diameter fiber cores. FiberPol aims to achieve a polarimetric accuracy of 0.1 % per spectral resolution bin. Further, it can also function as a non-polarimetric integral-field unit. The primary science goals include study of ISM of nearby galaxies to test the models of dust grain alignment and its dependence with the ambient magnetic field. The instrument design has been completed and it is currently being assembled and characterized in the lab. It is scheduled for on-sky commissioning in the second half of 2024. In this talk, I will present the scientific and technical goals of FiberPol, its overall design and initial results from the lab assembly and testing. FiberPol is a low cost technology demonstrator for 10m SALT and other large telescopes such as the 30m class telescopes. It can be modified and replicated for use on any existing spectrograph, especially on bigger telescopes.

Chandrayaan-3 Mission: Exploring the Moon

Date: 2024-07-26
Speaker: Dr. S. Vijayan
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Chandrayaan-3 mission successfully landed on the south pole/high latitude region of the Moon overcoming all the challenges during the landing. One of the major challenges in landing from this high latitude region is the high density of impact craters with various diameter ranges. This high density of impact craters was used to understand and explore this region in detail. Also this high latitude region is not explored by any insitu lander/rover and thus Chandrayaan-3 provided the first insitu insights about the lunar highland terrain near the south pole region. In this talk, I will be providing some new insights from the Chandrayaan-3 landing site region, which will unravel the unexplored part of this landing site. I will also highlight the source materials located within and around the Chandrayaan-3 site, which are crucial to interpret the insitu derived measurements. Chandrayaan-3 landing site region have been extensively reworked/modified by the impacts and the redistribution of material affected the lunar crust over this region extensively. In this talk, I will also discuss other landing site insitu images and bring out how the Chandrayaan-3 landing site region is similar/different from the other parts of the Moon.

Graphitisation for Radiocarbon Dating : Advancement with AGE-3 & challenges

Date: 2024-07-23
Speaker: Mr. Ankur Dabhi
Venue: Ground Floor Lecture Hall

Abstract

Radiocarbon dating is a widely used dating technique in earth sciences and archaeology. 1MV Accelerator Mass Spectrometer at PRL has been successfully measuring radiocarbon in variety of natural samples. Graphitisation is a crucial step in radiocarbon dating, enabling the transformation of carbonaceous samples into a form suitable for AMS. Graphitisation with Automated Graphitisation Equipment(AGE-3) is an innovative approach designed to enhance the efficiency and accuracy of graphitisation. In this talk, I will discuss the procedural advancements and optimization of AGE3, pre-treatments for different organic and inorganic samples which streamlines carbon extraction and reduces contamination ,the challenges with AGE3 and some results showing the quality & reliablity of graphite produced with AGE-3.

Signature of the vertical mixing in the atmosphere of hydrogen hydrogen-dominated exoplanet atmospheres

Date: 2024-07-19
Speaker: Dr. Vikas Soni
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The disequilibrium processes in an exoplanet's atmosphere can alter the atmospheric composition from its thermochemical equilibrium abundance. The strength of these processes depends upon the several physical parameters. The characterization of the atmosphere of exoplanets has entered a phase where the observed spectral signature can probe the disequilibrium chemistry in the atmosphere of this exoplanet. Atmospheric retrieval is commonly used to constrain atmospheric abundance and parameters. Retrieval models employ the observed spectrum to constrain parameters by navigating an N-dimensional parametric space through numerous forward models. However, the effect of disequilibrium processes in the observed spectrum of exoplanets depends upon the planet to planet. In this talk, I will discuss the atmospheric retrieval model and how one can use these models to find atmospheric parameters from the observed spectrum. I will also share my recent finding on constraining the strength of vertical mixing through atmospheric retrieval. In this study, we have explored the signature of disequilibrium chemistry in the parameter space of Kzz, surface gravity, internal temperature, metallicity and equilibrium temperature. We explore the retrieval model's effectiveness, including the vertical mixing as a quenching approximation. We run several 1D chemical kinetics models in large parameters and explore the excess in the transmission signature due to the vertical mixing. We run the retrieval model for the JWST simulated spectrum and explore how effectively the excess signature of the vertical mixing can constrain Kzz.

Multi-wavelength study of Blazars

Date: 2024-07-18
Speaker: Dr. Avik Kumar Das
Venue: Online : https://imeet.vconsol.com/join/5555049068?be_auth=NzQwNjQ0

Abstract

Blazars are a special subclass of active galactic nuclei, with relativistic jets pointing close to observers’ line of sight, making them the most luminous and rapidly variable extra-galactic sources in the universe. Their observed emissions are highly Doppler boosted and observable across the entire accessible electromagnetic spectrum (from radio to gamma-rays), with diverse variability timescales ranging from minutes to years. The observed emissions imply extreme physical conditions that are beyond replication by any current or future terrestrial laboratory. Almost every aspect, from jet formation, collimation to gamma-ray production in the jets, is poorly understood. However, over the past decade, the availability of long-term, high-cadence data in the multi-wavelength regime (i.e., optical, X-ray, and gamma-ray) has been helpful in addressing some aspects of these issues through study of i) multi-wavelength flux and spectral variability on diverse time scales, ii) physical origin of quasi periodic oscillations (QPOs) observed in the light curves, iii) multi-wavelength flux distribution of Blazars. In this talk, we will discuss our recent interesting results on the above topics related to Blazar emission properties.

Late Quaternary Turbidite deposits in the eastern Bay of Bengal

Date: 2024-07-16
Speaker: Dr. Prajith
Venue: online

Abstract

The Bay of Bengal is an enormous repository of continent-derived sediments stored in the world’s largest submarine fan, the ‘Bengal Fan’. Huge loads of sediments from the Himalayas, Indo-Burman ranges, and Peninsular India were transferred to the deep sea through the submarine channels developed on the Bay of Bengal seafloor. Currently, only one channel is active in supplying sediment to the Bengal Fan, whereas other channels are disconnected (inactive) from the land. Much about the evolution of the fan and its controlling factors, particularly the timings of major fluctuations in turbidite activity, is unknown. This work is based on sedimentological, geochemical, and Sr-Nd isotopic records from a gravity core collected from the now-defunct submarine channel E7 in the Bengal Fan to examine the roles of various environmental factors on the growth of the fan. Our results suggest that turbidite deposition through channel E7 was active during 27 to 12 kyrs and hemipelagic sedimentation started from 12 kyr BP to present. This work highlights the complex interplay between the climate and coastal geomorphology in the growth of the fan.

Effects of disorder on flat bands of some tight binding models.

Date: 2024-07-12
Speaker: Bharathiganesh D.
Venue: Room no: 469 (Main Campus)

Abstract

The effects of disorder on condensed matter systems where electrons move from one site to another by means of quantum mechanical diffusion described by tight binding models has garnered a lot of interest recently. In one dimension disorders almost always leads to localisation of electrons for lattices of reasonably big size. On the other hand, geometry of the lattice may lead to localisation of electrons at particular sites due to the onset of flat bands. In this talk we will discuss a system where both these localisation effects are present i.e. effects of different disorders on a system with flat bands and the net result of these effects.

Chandrayaan-3 mission and way ahead: Observations, challenges and evaluations

Date: 2024-07-12
Speaker: Dr. Rishitosh Kumar Sinha
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The successful soft-landing of India’s third lunar exploration mission, Chandrayaan-3, was a life-changing moment. It taught numerous lessons, expedited the execution of state-of-the-art technologies, solidified current understanding, introduced new challenges, and eventually opened up a multitude of fresh opportunities for the entire generation of scientists working in the space domain. This mission has involved a significant amount of work in its realization, execution, and post-implementation stages. In this seminar, I will concentrate on the Chandrayaan-3 related work that has been done recently using data analysis from remote sensing. I will highlight the challenges faced and present my evaluations of recently published studies. Finally, I'll wrap up by highlighting important facets of lunar geology that, in my opinion, represent the most significant scientific gaps in our knowledge of the Moon's evolutionary past.

Minimal Z' for Radiative mechanism

Date: 2024-07-09
Speaker: Gurucharan Mohanta, SRF
Venue: Room no: 469 (Main Campus)

Abstract

We discuss a mechanism in which the masses of the third, second, and first generation charged fermions are generated at tree level, 1-loop, and 2-loop levels, respectively. In this mechanism, loop-induced masses are obtained through fermionic self-energy corrections induced by heavy gauge bosons of a new single flavorful $U(1)_F$ symmetry, which have flavor-violating interactions with Standard Model fermions. Phenomenologically, the flavor-violating couplings $Q_{ij}$ are desired to have $|Q_{12}|<|Q_{23}|,|Q_{13}|$ because constraints from $K^0$-$\overline{K}^0$ mixing and $\mu$-$e$ conversion in nuclei, involving first and second family fermions, are more stringent than others. We establish a framework to achieve this condition and quantify the optimal flavor violations required to implement the radiative mass generation mechanism.

Isotopic record of Earth's accretion and early evolution

Date: 2024-07-09
Speaker: Dr Nikitha Susan Saji
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Exploring scalar dark sector with Peceei-Quinn symmetry at the LHC.

Date: 2024-07-05
Speaker: Dr. Anupam Ghosh
Venue: Room no: 469 (Main Campus)

Abstract

The Inert Higgs Doublet model (IDM), assisted by Peccei-Quinn (PQ) symmetry, offers a simple but natural framework of a dark sector that accommodates Weakly Interacting Massive Particle (WIMP) and axion as dark matter components. Spontaneous breaking of $U(1)_{PQ}$ symmetry, which was originally proposed as an elegant solution to the strong charge-parity (CP) problem, also ensures the stability of WIMP through a residual $\mathbb{Z}_2$ symmetry. Interestingly, additional fields necessitated by PQ symmetry further enrich the dark sector. These include a scalar field proprietor for axion DM and a vector-like quark (VLQ) that acts as a portal for the dark sector through Yukawa interactions. Moreover, this combination of the axion and WIMP components satisfies the observed DM relic density and reopens the phenomenologically exciting region of the IDM parameter space where the WIMP mass falls between 100 - 550 GeV. We investigate the model-independent pair production of VLQs exploring this region at the Large Hadron Collider (LHC), incorporating the effects of next-to-leading order (NLO) QCD corrections. After production, each VLQ decays into a top or bottom quark accompanied by an inert scalar, a consequence of the residual $\mathbb{Z}_2$ symmetry. Utilising relevant observables with a leptonic search channel and employing multivariate analysis, we demonstrate the ability of this analysis to exclude a significant portion of the parameter space with an integrated luminosity of 300 $\text{fb}^{-1}$.

The cursed Eukaryotes!

Date: 2024-07-02
Speaker: Mr.Janaarthanan P A
Venue: Ground Floor Lecture Hall

Abstract

In spite of early rise of eukaryotic organisms about ~1800 million years ago, their diversification happened only after a billion year later. This retardation in evolution of eukaryotic organisms has been attributed to low atmospheric oxygen abundance and nutrient limited conditions in the oceans of that time. In this talk, I will be discussing the nitrogen isotope dynamics during this period and evaluate its impact on eukaryotic evolution.

A Cauldron of Light: Mars as seen in ultraviolet

Date: 2024-07-01
Speaker: Dr. Sonal Jain
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Tremendous new insights into the Martian atmosphere have been achieved in recent years by two ultraviolet spectrographs built at LASP: the Imaging Ultraviolet Spectrograph (IUVS) aboard the Mars Atmospheric and Volatile EvolutioN (MAVEN) mission, and the Emirates Mars Ultraviolet Spectrometer (EMUS) aboard the Emirates Mars Mission (EMM). Both instruments have far exceeded their design goals in science return. This has been accomplished in part through opportunistic and innovative observations, not in the original concept of operations. large quantity of data and provided insights on present-day processes at Mars including dayglow, nightglow, aurora, meteor showers, clouds, and solar-planetary interactions. In this presentation, IÂ will highlight key results obtained by IUVS and EMUS, including (1) mapping of thermosphere composition, structure, and variability, including effects of the global dust storm ; (2) a surprisingly high level of auroral activity of three types; (3) characterizing the dynamics using nightglow. We will present an overview of these results and a discussion of their implications for understanding Mars's atmospheric dynamics and evolution.

Physics Informed Neural Networks

Date: 2024-06-27
Speaker: Deepanshu Srivastava, SRF
Venue: Room no: 469 (Main Campus)

Abstract

Principles like symmetry and invariance are ubiquitous in physics and have significantly influenced machine learning. This seminar explores the integration of physics principles into neural networks for solving complex problems. The development of physics-informed neural networks is examined, focusing on algorithms enforced by physics knowledge to facilitate the discovery of new physics. Specifically, the role of equivariance is discussed, highlighting its contribution to model efficiency and interpretability. The seminar concludes with a discussion on leveraging these techniques in high energy physics and potential future advancements. This approach holds promise for significant improvements in both theoretical insights and practical applications within particle physics.

Exploring three-dimensional magnetic nulls in the solar atmosphere: Theory and Simulations

Date: 2024-06-26
Speaker: Yogesh Kumar Maurya
Venue: USO Seminar Hall

Abstract

A three-dimensional (3D) magnetic null is a location where the magnetic field is zero. These nulls are abundant and are known to be important magnetic topologies in the solar atmosphere, playing vital roles in phenomena such as magnetic reconnection, jets, and circular ribbon flares. However, the mechanisms behind the generation of 3D nulls in such a dynamic atmosphere are yet to be fully explored. Recent magnetohydrodynamics (MHD) simulations propose that magnetic reconnection is responsible for both generating and annihilating 3D nulls, starting from an idealized magnetic field with a single proper radial null. In this seminar, we will briefly discuss the summary of the above work, highlighting the importance, structure, and properties of 3D nulls. We will further delve into the applications of these understandings to a more realistic scenario, incorporating the field line complexities inherent to a complex active region with thousands of preexisting nulls, and discuss the results. Additionally, we will explore the theme with an initially chaotic magnetic field devoid of any 3D nulls and discuss the results.

Plasma Motion in Sunspots

Date: 2024-06-25
Speaker: Prof. Debi Prasad Choudhary
Venue: USO Seminar Hall

Abstract

In this talk, I shall present the results to determine three dimensional thermal, magnetic and flow structure of sunspots using spectropolarimetric diagnostic in multiple spectral lines. We have used the observations with the spectropolarimeters at the focal plane of the Dunn Solar Telescope and analysis tools such as inversion codes and magnetic field extrapolation techniques developed by our group. In a series of investigations, we determine the detailed properties of Inverse Evershed Flow. Our results show that these flows are aligned along magnetic field lines that connect the outer penumbra with the outer end of the moat cell in the form of arched loops. We find that there is a positive field strength difference and the negative temperature difference between the inner and outer end point connected by these magnetic arches. This pressure difference induces a flow towards the sunspot following the siphon flow principle, which is in quantitative agreement of the observed flow speeds and those predicted from the pressure balance equation. I shall also introduce the ongoing and future research goals of our group. We are developing an analysis package for spectropolarimetric observations for the following purpose. 1. Develop and apply LTE and NLTE inversion codes to extract stratifications of temperature, velocity and magnetic field structure using multiple chromospheric and photospheric lines. 2. Develop an analysis tool for observations of the Halpha line. 3. Develop an automatic technique for integrating the piecewise continuous results of the H, He I at 1083 nm, and other lines into the analysis for a physically consistent stratification. 4. Determine magnetic and thermal atmospheric properties of sunspots for a full characterization of the solar atmospheric structure and its temporal evolution.

Radiocarbon in soil organic carbon and soil CO2 in a semi-arid tropical region of western India: implications to tropical soil carbon dynamics

Date: 2024-06-25
Speaker: Mr. Ranjan Mohanty
Venue: Ground Floor Lecture hall

Abstract

The exchange flux between the soil and the atmosphere is the largest carbon flux (~110×1015 g/yr) making it one of the most important components of global climate change on decadal to century scales. Therefore, it is very important to understand the dynamics of carbon in soil as a slight imbalance in the flux can drastically change the climate. We measured radiocarbon in soil organic matter and soil CO2 to estimate SOC turnover time and sources of CO2 in soils in forests and agricultural lands of Gujarat to assess the role of climatic conditions on SOC turnover time and identify major contributors responsible for CO2 emission from the soil. Results indicate that SOC contents and turnover times in tropical semi-arid soils are significantly influenced by precipitation, vegetation density and land use changes which I will discuss in this talk.

Design and Development of Processing Electonics for Dust EXperiment On-board POEM-3

Date: 2024-06-21
Speaker: Ms. Rashmi
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

ust is a major constituent in any planetary system and it is found everywhere in the solar system. Dust EXperiment (DEX), an Impact Ionization Dust Detector, is being developed for detection of these dust particles. DEX was recently flown in PS4 Orbital Experimental Module (POEM-3) of PSLV-C58, launched on 01 January 2024. POEM is the spent PS4 stage (fourth stage of PSLV) to carry out in-orbit scientific experiments for an extended duration. In this seminar, the speaker will discuss the design and development of the Processing Electronics of DEX. Also, the communication protocol (RS485) used in POEM will be discussed.

Probing the Physics of Radiation and Particles Emitted During Energetically-Rich Solar Flares

Date: 2024-06-21
Speaker: Dr. Arun Kumar Awasthi
Venue: USO Seminar Hall

Abstract

Solar flares are one of the earliest observational signature of solar eruptions. Although the X-class flares are the largest in intensity class, weak (micro/nano) flares are more frequent, making them a suitable candidate for coronal heating. By reconciling multi-wavelength observations, the standard flare energy release scheme to put forth the physical mechanism responsible for the production of emission and charged particles during flares. However, this scheme is often challenged by the observations, particularly during weak flares. Essentially, it is yet to be understood if the weak flares are just a scaled down version of large flares in the sense of physical processes. In this context, I will provide an overview of the research investigation conducted by us revealing the role of weak flares as unique tracers of pre-eruptive plasma and magnetic field environment. I will also provide an overview of future plans associating the physics of solar flares with the initiation mechanism of the coronal mass ejections with an emphasis on combining the observations from the ADITYA-L1 and the Solar orbiter missions.

Relativistic hydrodynamics and its applications in heavy-ion collisions

Date: 2024-06-20
Speaker: Dr. Chandrodoy Chattopadhyay,
Venue: Online---https://imeet.vconsol.com/join/3016457289?be_auth=MzgwMTgw

Abstract

Relativistic heavy-ion collisions at LHC, CERN and RHIC, BNL produce a novel state of matter, the quark-gluon plasma (QGP), where the fundamental constituents of nucleons, i.e., quarks and gluons, become deconfined over nuclear volumes. Understanding the thermodynamic and transport properties of QGP constitute one of the major goals of high energy nuclear physics. Research over the last two decades has established that the bulk evolution of QGP can be remarkably well-described by relativistic hydrodynamics. Although it is traditionally believed that hydrodynamics is applicable only for nearly-equilibrated systems, recent discoveries reveal that it may be successful even for far-off-equilibrium stages of heavy-ion collisions. This leads to a fundamental question pertaining to many-body dynamics: when does a macroscopic system depict hydrodynamic behavior? In this talk I shall present modern formulations of hydrodynamics and use the concept of `non-equilibrium attractors’ to discuss why such formulations are unreasonably effective beyond their expected domain of applicability. I will then present `maximum-entropy hydrodynamics’, a macroscopic theory which can describe both near and far-off-equilibrium regimes of heavy-ion collisions in a single framework. Finally, I will discuss formulations of stochastic hydrodynamics and its extensions to model the evolution of critical fluctuations in a system that is close to a critical point.

Precision in Motion: Fabry-Perot Etalon as a Wavelength Calibrator for Extreme Precision Radial Velocity Methods

Date: 2024-06-20
Speaker: Shubhendra Nath Das
Venue: Seminar Room # 113/114 (Thaltej campus)

Abstract

To date, over 5500 exoplanets have been observed, with the radial velocity method, utilizing Doppler shifts in light, proving its effectiveness. Advancements in spectrograph technology now enable us to detect and analyze subtle Doppler signals, potentially leading to the discovery of Earth-like exoplanets. However, challenges remain, particularly in wavelength calibration techniques. To address this, we propose a new approach utilizing Fabry-Perot etalons (FPE) in conjunction with PRL's cutting-edge spectrograph, PARAS-2. In this presentation, we will discuss recent advancements, including calculations regarding pressure and temperature stability, and showcase the design of the optomechanical assembly for the FPE.

Deformation of the Gruithuisen Region Lava Tube under Compressional Stress on the Moon

Date: 2024-06-14
Speaker: Ms Kimi Khungree Basumatary
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Lunar lava tubes have gained considerable attention due to their potential as habitable spaces for future missions. These naturally occurring tunnels provide a shield against extreme temperature variations, radiation, and micrometeorite impacts, making them attractive candidates for potential human bases. One unique lava tube is located in the Gruithuisen region (~35°E, 44°W) on the Moon, characterised by a series of collapsed pits and raised formations. Morphometric analysis reveals eight distinct morphologies, ranging from curvilinear channels to elliptical shapes, while the existence of wrinkle ridges in the study area indicates that the area is subjected to compressive stress. This study employs numerical simulations to investigate how a lava tube responds to compressional stress. The results closely replicate the deformations observed in the Gruithuisen region lava tube, emphasising the significant role of compressional stress in its deformation. These models suggest that the eight unique features result from variations in displacement magnitude and direction along three axes (X, Y, and Z). Our research sheds light on the structural changes in lava tubes under varying compressional stress, enhancing our understanding of how the interplay between tectonic activity and the lava tube has shaped the Moon's surface. In this seminar, I will discuss the importance of this study, the challenges faced during the simulation, and the detailed outcomes.

Origin of granitoids from the Chitradurga greenstone belt: Constraints from geochemical modelling

Date: 2024-06-13
Speaker: Dr. Sibin Sebastian
Venue: Online

Abstract

The Chitradurga greenstone belt was intruded by potassic granite and low-K trondhjemite during the Neoarchean. Understanding their origin has implications on reworking of crust and stabilization of the western Dharwar craton. Geochemical and Nd isotopic data suggest partial reworking of different pre-existing crustal lithology. Tonalite-Trondhjemite-Granodiorite (TTG) gneisses represent the most abundant lithology and basement rocks of the craton. Partial melting of TTG gneisses and differentiation of melt resulted in compositionally different potassic granite. Simultaneously, partial melting of metabasites resulted in the formation of trondhjemite. The extent of melting and differentiation are quantified through numerical modelling. Quantitative modelling attests low temperature melting of crustal rocks at different depths and the modification of melt by fractional crystallization during ascent for the formation of the studied rock types. Such reworking event was likely triggered by mafic underplating and H2O dominated fluid flux.

Discovery and Characterization of a Dense Sub-Saturn TOI-6651b

Date: 2024-06-10
Speaker: Sanjay Baliwal
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The sub-Saturn classification of exoplanets refers to planets larger than Neptune but smaller than Saturn, typically falling within the range of 4-8 Earth radii. Sub-Saturns are considered failed gas giants with equally massive cores but significantly smaller total masses, having accreted envelopes that are much less than their cores. The absence of these planets in our solar system highlights the variety of possible planetary systems, and studying them around other stars provides valuable insights into this diversity. In this talk, I will discuss our recent discovery of a sub-Saturn TOI-6651b using PARAS-2 spectroscopic observations. TOI-6651b is transiting around a sub-giant, metal-rich G-type star in a ~5.06 day orbit. Joint fitting of the radial velocities from PARAS-2 and transit photometric data from TESS revealed planetary mass of ~59.4 Earth masses and a radius of ~5.30 Earth radii. TOI-6651b has a bulk density of ~2.18 g cm-³, positioning it among the select few known dense sub-Saturns and notably the densest among those detected with TESS. We find that a considerable portion ~85% of the planet's mass consists of dense materials such as rock/iron in the core, while the remaining mass comprises a low-density envelope of H/He. The existence of TOI-6651b challenges conventional planet formation theories and could be a result of merging events or significant atmospheric mass loss through tidal heating.

SMEFT analysis of charged lepton flavor violating B-meson decays

Date: 2024-06-10
Speaker: Dr. N Rajeev
Venue: Online---https://imeet.vconsol.com/join/6642133707?be_auth=Mjc4NjM0

Abstract

Charged lepton flavor violation (cLFV) processes, potentially important for various Beyond the Standard Model Physics scenarios are analyzed in the Standard Model Effective Field Theory (SMEFT) framework. We consider the most relevant 2 quark-2 lepton (2q2ℓ) operators for the leptonic and semi-leptonic LFV B-decay (LFVBD) processes Bs → µ +e −, B+ → K+µ +e −, B0 → K∗0µ +e −, and Bs → ϕµ−e +. We analyse the interplay among the Wilson coefficients responsible for these LFVBDs and other cLFV processes like CR(µ → e), ℓi → ℓjγ, ℓi → ℓj ℓkℓm and Z → ℓiℓj, to find the maximal possible LFV effects in B-meson decays. We probe the scale of new physics in relation to the constraints imposed by both classes of the LFV decays while considering both the present bounds and future expectations. In view of the proposed experiments at LHCb-II and Belle II to study charged LFV processes, we have also provided the upper limits on the indirect constraints on such LFVBDs. For the processes where B meson is decaying to µ ± and e ∓, we show that new physics can be constrained by an enhancement of 2-4 orders of magnitude on the current sensitivities of the BRs of B+ → K+µ +e −, B0 → K∗0µ +e −and Bs → ϕµ±e ∓.

Unravelling Mar’s Magmatic Past: Insights from Martian Shergottites

Date: 2024-06-07
Speaker: Ms Varsha M Nair
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Shergottites, constituting around 90% of the Martian meteorite collection, are categorized based on texture and mineralogy into various types, including basaltic, olivine-phyric, poikilitic, and gabbroic. Notably, poikilitic shergottites exhibit a distinctive bimodal texture, providing insights into their evolutionary trajectory, marked by an initial slow-cooling poikilitic stage followed by a rapidly cooled interstitial stage. Given their potential abundance in the Martian crust, these meteorites are crucial in studying Martian magmatism. This study delves into the mineralogy, petrology, and olivine-hosted melt inclusions of two poikilitic shergottites, NWA 7397 (enriched) and NWA 1950 (intermediate).

Understanding the Role of magnetic fields in the G47 filamentary cloud

Date: 2024-06-06
Speaker: Omkar Jadhav
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Several observational studies have shown that filaments are active sites of star-formation which makes them ideal laboratories to study the physical processes involved. However, star-formation remains a highly complex process, which is driven by an interplay between gravity, turbulence, magnetic fields, and stellar feedback. Among these, the exact role of magnetic fields in the process of star-formation and its interplay with other factors is the least understood. In this talk I will try to address two main questions: What role do magnetic fields play in the star formation process in filaments? How does stellar feedback affects the morphology of magnetic fields in filaments? Subsequently, I will present findings from our ongoing research on the factors responsible for driving the star-formation in the G47 filamentary cloud.

Mathematical tales of blackhole, gravity and machine learning

Date: 2024-06-06
Speaker: Dr. Arghya Chattopadhyay
Venue: Online---https://imeet.vconsol.com/join/9420300322?be_auth=MTQzNjAy

Abstract

The aim of this talk is to elaborate on the key concepts of my current research and to outline my future research plans during and beyond the Ramanujan fellowship. I will begin by explaining the basics of quantum complexity with simple examples, followed by an intriguing relationship between the algebra of triple systems and the entropy of black holes in 5 and 4 dimensions. Following this, I will discuss our recent observations in these fields, highlighting notable findings and their implications. Next, I will delve into the bare essentials of machine learning (ML), motivating how principles from physics can enhance ML algorithms. This will be followed by an overview of the two avenues of my research plan: theoretical development and machine learning. I will conclude with a brief discussion on the potential impact and future scope of the proposed research plan for Ramanujan Fellowship.

On the Response of Transition Region and Corona to Rapid Excursions in the Chromosphere

Date: 2024-06-04
Speaker: Mr. Ravi Chaurasiya
Venue: USO Seminar Hall

Abstract

Spicules are the thin, hair/grass-like structures that are prominently observed at the chromospheric solar limb. It is believed that fibrils and Rapid Blue and Red Excursions (RBEs and RREs; collectively referred to as REs) correspond to on-disk counterparts of type I spicules & type II spicules, respectively. Our investigation focuses on observing the response of these REs alongside similar spectral features in the chromosphere, transition Region (TR), and corona, utilizing space-time plots derived from co-ordinated observations from SST/Hα, IRIS, and SDO. Our analysis reveals upflowing REs, promptly reaching temperatures characteristic of the TR and corona, indicating a multi-thermal nature. Similarly, downflowing features exhibiting similar spectral signatures over the disk display plasma motion from the corona to chromospheric temperatures, demonstrating a multithermal nature. In addition to distinct upflows and downflows, we observe sequential upflow and downflow along the same path, depicting a distinctive parabolic trajectory in space-time plots of observations sampling TR and various coronal passbands. Similar to isolated upflows and downflows, these REs also exhibit a multi-thermal nature throughout their trajectory. Furthermore, our results reveal a more intricate motion of the REs in which both upflow and downflow coexist at the same spatial location. On a different note, our analysis, utilizing coordinated IRIS spectral observations, shows spatio-temporal redshifts/downflows in both the TR and chromosphere due to the upper atmosphere flow of plasma in the form of bundles of spicules or features exhibiting similar spectra. Our analysis suggests that at least subsets of the strong redshifts/downflows observed in TR temperature spectra are due to these bundles of spicules or features exhibiting similar spectra.

Deciphering the Mysteries of the Long-Lived Particles at the colliders

Date: 2024-06-03
Speaker: Ms. Chandrima Sen
Venue: Online--- https://imeet.vconsol.com/join/4524798341?be_auth=OTExNTQ0

Abstract

Conventional searches at the LHC operate under the assumption that Beyond the Standard Model particles undergo immediate decay upon production. However, this assumption lacks inherent a priori justification. This talk delves into the exploration of displaced decay signatures across various collider experiments. Combining insights from several studies, we show how small Yukawa couplings, compressed mass spectra, and collider boosts lead to distinctive displaced decays, observable at the CMS, ATLAS and proposed future detectors. These phenomena, manifesting within both Type-I and Type-III seesaw mechanisms, and the Vector-like lepton model with non-zero hypercharge, provide a unique insight into the behaviors of neutrinos and dark matter. The seminar highlights the technical challenges and breakthroughs in detecting and interpreting these signatures, emphasizing their significance in probing the depths of the extensions of the Standard Model.

CHALLENGES INVOLVED IN THE DEVELOPMENT OF X-RAY ASTRONOMY TELESCOPES

Date: 2024-05-30
Speaker: Neeraj K. Tiwari
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The advancement in X-ray astronomy is directly linked to the high-sensitivity observations primarily provided by X-ray telescopes. The fundamental parameters of X-ray telescopes, such as effective area, angular resolution, field of view, and energy response, define observational sensitivity. Significant improvement has been achieved in these parameters over the past few decades. However, further enhancement from a basic design perspective is constrained by the fact that X-ray reflection occurs only at grazing incident angles. This limitation leaves only the option for further improvement by reducing the geometrical uncertainty associated with X-ray mirrors. In this talk, I will discuss the role of X-ray telescopes in X-ray astronomy, their working principles, the possibility of improvement through design, various fabrication methods, metrology, along with their limitations.

Insights into the major sources and formation pathways of p-NO3- using dual isotope proxy

Date: 2024-05-30
Speaker: Ms. Chandrima Shaw
Venue: Ground Floor Lecture Hall

Abstract

NOx plays a significant role in atmospheric chemistry, influencing air quality, human health, climate change. It contributes to the formation of particulate matter (p-NO3-), tropospheric ozone, acid rain, and smog, while also serving as a nutrient for both oceanic and terrestrial ecosystems. Despite its significant role, the sources of NOx and its conversion pathways to p-NO3- remain poorly understood both globally and regionally (South-East Asia). Dual isotopes (δ18O and δ15N) of p-NO3- can serve as a powerful tool to understand the formation pathways of p-NO3- and sources of NOx. In this talk I will discuss the application of dual isotopes (δ18O and δ15N) of p-NO3- in understanding the atmospheric chemistry and sources related to p-NO3- and NOx

On the nature of Hub-Filament Systems in Galactic "Snake" IRDC G11.11-0.12

Date: 2024-05-28
Speaker: Dr. Naval Kishor Bhadari
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Hub-Filament Systems (HFSs) are complex, web-like structures of filaments within molecular clouds and are widely known as nurseries for massive stars. While there is evidence of mass transfer from the molecular clouds to the hub through filaments, the exact driving factors of this process remain poorly understood. In this talk, I will review the current understanding of HFSs and present the findings from our ongoing work on the Galactic 'Snake' IRDC G11.11-0.12, which is known to host multiple HFSs. I will conclude by discussing how HFSs act as efficient material collection systems, ultimately favouring the formation of star clusters, including massive stars.

On the Response of Transition Region and Corona to Rapid Excursions in the Chromosphere

Date: 2024-05-27
Speaker: Mr. Ravi Chaurasiya
Venue: USO Seminar Hall

Abstract

Spicules are the thin, hair/grass-like structures that are prominently observed at the chromospheric solar limb. It is believed that fibrils and Rapid Blue and Red Excursions (RBEs and RREs; collectively referred to as REs) correspond to on-disk counterparts of type I & type II spicules, respectively. Our investigation focuses on observing the response of these REs alongside similar spectral features in the chromosphere, transition Region (TR), and corona, utilizing space-time plots derived from co-ordinated observations from SST/H-alpha, IRIS, and SDO. Our analysis reveals upflowing REs, promptly reaching temperatures characteristic of the TR and corona, indicating a multi-thermal nature. Similarly, downflowing features exhibiting similar spectral signatures over the disk display plasma motion from the corona to chromospheric temperatures, demonstrating a multithermal nature. In addition to distinct upflows and downflows, we observe sequential upflow and downflow along the same path, depicting a distinctive parabolic trajectory in space-time plots of observations sampling TR and various coronal passbands. Similar to isolated upflows and downflows, these REs also exhibit a multi-thermal nature throughout their trajectory. Furthermore, our results reveal a more intricate motion of the REs in which both upflow and downflow coexist at the same spatial location. On a different note, our analysis, utilizing coordinated IRIS spectral observations, shows spatio-temporal redshifts/downflows in both the TR and chromosphere due to the upper atmosphere flow of plasma in the form of bundles of spicules or features exhibiting similar spectra. Our analysis suggests that at least subsets of the strong redshifts/downflows observed in TR temperature spectra are due to these bundles of spicules or features exhibiting similar spectra.

Analysis of surface temperatures obtained from Chandrayaan-2 Imaging Infra-Red Spectroscopy (IIRS) data and comparison with LRO-Diviner data

Date: 2024-05-24
Speaker: Dr. Subhadyouti Bose
Venue: SEMINAR ROOM NO # 113/114 (THALTEJ CAMPUS)

Abstract

Imaging Infra-Red Spectrometer (IIRS), launched onboard Chandrayaan-2 on July 2019, is an advanced hyperspectral spectrometer that captures high-resolution images of the lunar surface at a spatial resolution of 80 m/pixel with a high spectral resolution of 20 nm. The spectral range of IIRS extends from 0.7 µm to 5 µm and includes 250 spectral bands. Calibrated IIRS radiance data have been used to estimate surface temperatures at different locations on the Moon. In this study, I will present results obtained from IIRS data as well as discuss results from a comparative analysis with LRO-Diviner as well as Chandrayaan-1 Moon Mineralogy Mapper (M3) data.

Propagation and damping of slow magnetoacoustic waves from photosphere to corona along the fan loops rooted in sunspot umbra

Date: 2024-05-21
Speaker: Ms. Ananya Rawat
Venue: USO Seminar Hall

Abstract

Coronal fan loops rooted in sunspot umbra constantly show propagating slow magnetoacoustic waves (SMAWs) of various periods in the corona. However, the origin of these waves found along the whole umbral atmosphere is still unclear. Here, we studied these waves along a clean fan loop system using multi-wavelength imaging and spectroscopic observations from SDO and IRIS. We traced the origin of 3-min waves at the photosphere by utilizing amplitude and frequency modulations of 3-min waves from the corona to the photosphere. This loop tracing also provides the first observational evidence of loop area divergence with height in the umbral atmosphere. We calculated the energy flux of these waves with height in the umbral atmosphere and further obtained the damping lengths of SMAWs propagating along the fan loops to be approx. 208 km and 170 km for 3-min and 1.5-min periods respectively. To investigate the role of area expansion on the damping of these SMAWs, we calculated the total wave energy content within the loop cross-sectional area at each atmospheric height. We further deduced the damping lengths of total wave energy content to be approx. 303 km and 172 km for 3-min and 1.5-min period waves respectively, and thus present the actual damping of SMAWs after taking into account the geometric effect of area expansion of the loops. Our finding highlights the role of loop expansion and frequencies in the damping of SMAWs from the photosphere to corona along fan loops.

Scientific computing with open source: An in-house developed Software for PRL-AURiS Data Exploration

Date: 2024-05-21
Speaker: Ms. Pratheeksha Nayak
Venue: Ground Floor Lecture Hall

Abstract

Use of open source tools can play a pivotal role in scientific computing by providing robust, flexible solutions for various data analysis tasks. Python, with its extensive libraries and frameworks, is particularly well-suited for scientific computing. SPADE (Software for PRL-AURiS Data Exploration) is a web application developed using Python to enable computation of radiocarbon age estimates using the raw data from the 1 MV Accelerator Mass Spectrometer(AMS) at PRL. It is the first step in the development of a software suite for various data treatment and analysis protocols that can be implemented on data obtained from AMS. SPADE has an interactive interface and can be deployed anywhere without the need to install Python or any of its packages. In this talk, I shall discuss the nature of the raw data, workflow of the data processing pipeline, the details of implementation and the future objectives of SPADE.

Physical and Chemical Properties of Stratospheric Aerosols using Balloon Borne Instruments

Date: 2024-05-14
Speaker: Dr. Gwenael Berthet
Venue: Online

Abstract

Aerosol particles of the stratosphere are key components of the Earth’s radiative balance and of the processes controlling the ozone layer. They have various sources, both of anthropogenic and natural origin, more or less sporadic like volcanic eruptions and intense wildfires. We will present an overview of the knowledge of stratospheric aerosols regarding their chemical and physical properties with a specific focus on in situ observations from balloon-borne instruments (optical particle counters, backscatter sondes, aerosol collectors) launched from various locations on the globe. These measurements, together with space-borne observations and chemistry-transport model simulations, show particles of different sizes and types like sulphuric acid droplets, organics, nitrates, meteoric material with proportions dependent on seasons and regions. Specifically, we will show results from balloon campaigns (called BATAL) conducted by TiFR in India from Hyderabad.

Exploring Reconnection in Data-Based MHD Simulations of Solar Flares

Date: 2024-05-13
Speaker: Mr. Satyam Agarwal
Venue: USO Seminar Hall

Abstract

Solar flares are believed to be the manifestation of magnetic reconnection, dissipating magnetic energy in the form of heat, kinetic energy of plasma, and particle acceleration. As a result, the net magnetic energy of the magnetofluid decreases. Further, reconnection changes connectivity of magnetic field lines with respect to the plasma parcels, causing a topological reconfiguration. To explore reconnection and its implications, we perform data-based MHD simulations of flares. In this regard, notable is the use of magnetic field extrapolation for modeling the magnetic field in active-regions. The extrapolated field is utilized as an initial condition for the MHD simulation. In the presence of two contemporary models, namely the nonlinear force-free field (NLFFF) and non force-free field (NFFF), it is imperative to explore the effect of these two varying models on reconnection and consequently on the simulated dynamics of flares. Further, owing to decrease of magnetic energy during flares, the magnetofluid is expected to relax toward an equilibrium of lower energy. Consequently, the simulated dynamics merits interest from the perspective of MHD relaxation theory also. Toward such explorations, we investigate the data-based simulation of solar flares and in this seminar, I will be discussing the results of these studies.

High precision Al-Mg isochron of calcium Aluminium Rich Inclusions from IMS-1280

Date: 2024-05-10
Speaker: Ankit Prakash Singh
Venue: SEMINAR ROOM NO # 113/114 (THALTEJ CAMPUS)

Abstract

Calcium Aluminium rich Inclusions are one of the first formed solids of our solar system ~4568.7 myr. It is suggested that 26Al, an SLR (which decays into 26Mg) with a half-life of 0.717 Myr, was homogenously distributed throughout in the solar system. For this reason, the initial abundance of 26Al is widely used to determine the relative chronology of the early solar system. Using the Al-Mg systematics, the primitive CAIs are identified which will be further analyzed for Ca-K systematics. In this talk, I will present the high-precision SIMS data obtained for Al-Mg systematics from IMS 1280 at CRPG, Nancy. Further, I will talk about the Ca-K systematics and standard run that was done at high mass resolution to remove the isobaric interferences. The dataset obtained from the standard run resulted in the deliberation and preparation of new synthetic standards of refractory minerals of varying Ca/K ratios.

Impact of mass transfer rate on the behaviour of cataclysmics

Date: 2024-05-09
Speaker: Aakash
Venue: Seminar Room #113/114 (Thaltej Campus)

Abstract

The transfer of mass between the two stellar components via an accretion disc, a characteristic of cataclysmic variables (CVs), gives rise to various intriguing astrophysical phenomena such as nova, dwarf nova, etc. It appears that the rate at which this transfer of mass takes place plays a significant role in the dwarf nova cycle and the behaviour of cataclysmics in general. Depending on it, a CV may show characteristics of a dwarf nova with semi-regular outbursts or a novalike variable. The canonical evolution model of cataclysmics suggests that different mechanisms are responsible for driving the mass transfer above and below the period gap (2 hr ≲ Porb ≲ 3 hr). However, the reduction and enhancement in the mass transfer rate (e.g. novalikes) and the underlying causes are still not understood well. In this talk, I will discuss the response of a cataclysmic system to different mass transfer rates. I will also present the calculation of mass transfer rate for the long period dwarf nova system V1948 Cyg and discuss how the results accord with the disc instability model.

Impact-induced textures and phase transformations in shocked Indian meteorites.

Date: 2024-05-03
Speaker: Dr. Kishan Tiwari
Venue: ROOM NO 113 (THALTEJ CAMPUS)

Abstract

Hyper-velocity impact between planetary bodies induces high-pressure and high-temperature conditions triggering polymorphic transformation within the impacted materials. Moreover, such impacts lead to the fragmentation of the impactor with fragments dislodged in all directions. Some of these fragments eventually fall on Earth as shocked meteorites. Here, I will present my analysis of shocked Indian meteorites. I will discuss different high-pressure phases and shock-induced textures present in these meteorites and their formation conditions.

Atmospheric Water Vapor Dynamics at Guru Shikhar, Mt. Abu, the highest point of the Aravalli Range, Rajasthan

Date: 2024-04-30
Speaker: Mr. Virendra R. Padhya
Venue: Ground Floor Lecture Hall

Abstract

The stable isotope ratios (δ18O and δD) of water vapor are used to characterize continuous variations in large-scale and boundary-layer atmospheric processes. We carried out continuous measurements of δ18O and δD in Ground level water vapor at Gurushikhar, Mount Abu, Rajasthan, from Feb 2023 to Feb 2024 to understand how large-scale and local atmospheric processes influence variations in water vapor δ18O and δD on daily to seasonal time scales. Most of the variabilities are associated with the transition between the Indian summer monsoon and the westerlies, which transport distinct moisture to the study area. The local temperature, specific humidity and boundary layer height impact the diurnal variations in water vapor δ18O. The data reveal interesting seasonal and diurnal atmospheric phenomena which will be discussed in the talk.

Enhancing Geological Insights: Information-Theoretic Analysis of REE Concentrations for Rock Discrimination and Source Provenance Studies

Date: 2024-04-23
Speaker: Mr. Shivansh Verma
Venue: NanoSims Hall

Abstract

In the past decade, the application of information-theoretic methods has substantially enhanced our understanding of intricate complex processes. In this talk, I will discuss one such method based on Kullback-Leibler (KL) divergence, which utilizes Rare Earth Elements (REEs) concentrations to identify the similarities and differences among co-existing rocks of any given complex. In case of igneous rocks, the order of KL-divergence effectively distinguishes between rocks that have undergone different degrees of physical differentiation during their genesis. Moreover, when employed in conjunction with isotopic data, the method can yield robust constraints for source provenance studies in the context of sedimentary rocks. I will also discuss the differences between the KL-divergence method and Principal Component Analysis (PCA), highlighting the unique information provided by the former

The Highlights Of 55th Lunar And Planetary Science Conference (LPSC-2024)

Date: 2024-04-19
Speaker: Mr. Trinesh Sana & Dr. Subham Sarkar
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Mr. Trinesh Sana and Dr. Subham Sarkar attended the 55th Lunar and Planetary Science Conference (LPSC-2024) held from 11th to 15th March 2024 at the Woodlands, Houston, Texas, United States of America. This conference brings together international specialists in petrology, geochemistry, geophysics, geology, and astronomy to present the latest research results in planetary science. The conference is organized jointly by the Lunar and Planetary Institute and NASA. The meeting provides a unique opportunity for scientists from around the world to talk about the latest results of their research and current planetary science missions. Trinesh presented his recent work regarding Dust Charging Within Lunar Photoelectron Sheath. Subham delivered a talk about the maiden detection of Natrolite on Mars using Perseverance Rover Data. Apart from presenting in their own sessions, they have attended various other sessions covering topics to their interests. In this seminar, these two young researchers will share their experiences and knowledge gathered from the conference.

New Ways to Detect Light Dark Matter

Date: 2024-04-19
Speaker: Dr. Anirban Das
Venue: Room no: 469 (Main Campus)

Abstract

In the last few years, direct detection of light sub-GeV dark matter has emerged as a frontier research area. Because of its low energy scales, many condensed matter systems have been proposed as possible target materials. In this talk, I'll briefly review the mechanisms behind a few of them, and introduce two novel ideas. First, to use superconducting quantum devices to measure the power deposition from dark matter scattering. I'll show that the existing data already put competitive limits on the dark matter-nucleon interaction. I'll also describe how bilayer graphene with voltage-tunable band gap can be used to probe sub-MeV dark matter-electron scattering with promising future prospects.

Dark Matter: the Enigma of our Cosmos

Date: 2024-04-18
Speaker: Dr. Anirban Das
Venue: Room no: 469 (Main Campus)

Abstract

We have known about the existence of a dark sector in our Universe for almost 100 years that comprises about 85% of all matter. However, we are still in the dark about its fundamental nature. In this talk, I will describe various evidences of dark matter that we have, and outline a few theoretical ideas to explain its cosmic abundance. Finally, I will give an overview of various experimental endeavors to identify it, such as direct, indirect detection experiments etc.

Daksha: Indian Eyes on Transient Skies

Date: 2024-04-15
Speaker: Prof. Varun Bhalera
Venue: Seminar Room #113/114 (Thaltej Campus)

Abstract

Daksha is a proposed High Energy transients mission that will have higher sensitivity than any other mission in the world. Daksha will comprise of two satellites covering the entire sky from 1 keV to > 1 MeV. The primary objectives of the mission are to discover and characterize electromagnetic counterparts to gravitational wave sources; and to study Gamma Ray Bursts (GRBs). With its broadband spectral response, high sensitivity, and continuous all-sky coverage, it will discover fainter and rarer sources than any other existing or proposed mission. Daksha can make key strides in GRB research with polarization studies, prompt soft spectroscopy, and fine time-resolved spectral studies. In addition, Daksha is a versatile all-sky monitor that can address a wide variety of science cases. Daksha will provide continuous monitoring of X-ray pulsars. It will detect magnetar outbursts and high energy counterparts to Fast Radio Bursts. Using Earth occultation to measure source fluxes, the two satellites together will obtain daily flux measurements of bright hard X-ray sources including active galactic nuclei, X-ray binaries, and slow transients like Novae. Correlation studies between the two satellites can be used to probe primordial black holes through lensing. Daksha will have a set of detectors continuously pointing towards the Sun, providing excellent hard X-ray monitoring data. Closer to home, the high sensitivity and time resolution of Daksha can be leveraged for the characterization of Terrestrial Gamma-ray Flashes. In this talk, I will discuss the scientific impact of Daksha in all these areas

Cloud-Cloud Collision: Formation of Hub-Filament Systems and Associated Gas Kinematics

Date: 2024-04-12
Speaker: Arup Kumar Maity
Venue: Seminar Room #113/114 (Thaltej Campus)

Abstract

Massive star-forming regions (MSFRs) are commonly associated with hub-filament systems (HFSs) and sites of cloud-cloud collision (CCC). Recent observational studies of some MSFRs suggest a possible connection between CCC and the formation of HFSs. To understand this connection, we analyzed the magneto-hydrodynamic simulation data from Inoue et al. (2018). This simulation involves the collision of a spherical molecular cloud with a plane-parallel sea of dense molecular gas at a relative velocity of about 10 km/s. Following the collision, turbulent and non-uniform cloud undergoes shock compression, rapidly developing filamentary structures within the compressed layer. We found that CCC can lead to the formation of HFSs, which is a combined effect of turbulence, shock compression, magnetic fields, and gravity. The collision between the cloud components shapes the filaments into a cone and drives inward flows among them. These inward flows merge at the vertex of the cone, rapidly accumulating high-density gas, which can lead to the formation of massive star(s). The gas distribution in the position-velocity and position-position spaces highlights the challenges in detecting two cloud components and confirming their complementary distribution if the colliding clouds have a large size difference. However, such CCC events can be confirmed by the position-velocity diagrams presenting gas flow toward the vertex of the cone, which hosts gravitationally collapsing high-density objects, and by the magnetic field morphology curved toward the direction of collision. In this talk, I will present these initial results.

Dancing Lunar Dust

Date: 2024-04-12
Speaker: Mr. Trinesh Sana
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The Lunar Horizontal Glow, observed during the Surveyors and Apollo missions, unveiled the intricate dynamics of lunar dust movement. The movement of lunar dust, akin to "dancing," is primarily driven by electrostatic forces generated by the continual bombardment of charged particles from the solar wind and highly energetic UV photons on the lunar surface and dust particles. This celestial choreography is important for unravelling the fundamental processes governing surface evolution not only on the Moon but also across other airless bodies throughout the solar system.

Solar Wind Ion Spectrometer (SWIS), A miniature mass spectrometer onboard the Aditya-L1 mission: Objectives, Configuration, and Development

Date: 2024-04-09
Speaker: Mr. Pranav Adhyaru
Venue: NanoSims Hall

Abstract

The Solar Wind Ion Spectrometer (SWIS) is a subsystem of the ASPEX (Aditya Solar Wind Particle Experiment) payload, developed by PRL and one of seven payloads onboard the Aditya-L1 mission. The Aditya-L1 was launched in September 2023 and reached the Sun-Earth system's first Lagrangian point, L1, in January 2024. The primary focus of the ASPEX payload is to understand the Sun and solar wind processes as well as the acceleration and energization of the solar wind particles. ASPEX consists of two subsystems, SWIS and STEPS. The SWIS measures the particles in the energy range from 100 eV to 20 KeV, whereas STEPS works in 20 KeV to 5 MeV. SWIS is a miniature mass spectrometer customized for the space application to understand the origin of solar wind (slow and fast wind) and supra-thermal ions, thermal anisotropy, turbulence, and arrival of ICME (Interplanetary Coronal Mass Ejection) and SIR (Stream Interface Region) at L1 for space weather science and applications. In this seminar, I will highlight the science and technical objectives and configuration of the SWIS experiment. The design and development aspects of the High Voltage Power Supplies and Front-End-Electronics will also be discussed. The SWIS subsystem was switched on in December 2023 during the cruise phase of the Aditya-L1 for the performance verification of all its units. The data acquired during this phase and the preliminary results will also be presented.

Highly Siderophile Elements In Lunar Mantle And Crust Beyond The Procellarum KREEP Terrane

Date: 2024-04-05
Speaker: Mr. Yash Srivastava
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Volcanism and collisional impacts are the two primary processes that have shaped the terrestrial bodies of the Solar System. While these geological processes are ubiquitous across planetary bodies, the absence of an atmosphere and minimal active geologic processes (e.g., plate tectonics) on the Moon makes it the prime candidate for understanding these processes over a large timescale (~4.4 – 2.0 Ga). The absolute and relative abundances of the highly siderophile elements (HSE: Re, Os, Ir, Ru, Rh, Pt, Pd, and Au) have long been utilized to understand the volcanic and impact history of the Moon. Most of our current understanding of the abundance of highly siderophile elements (HSE) in the Moon comes from returned samples, which limits our insight. This motivates us to analyze additional samples, particularly those likely sourced away from the Procellarum KREEP Terrane (PKT), to better understand HSE abundance and Re-Os isotope variability in lunar crust and mantle reservoirs. In this talk, I will discuss the HSE and Re-Os isotopic abundance of four lunar meteorites, A-881757, Y-86032, Y 981031, and Y 983885, that are likely sourced away from the PKT region. The unbrecciated lunar meteorite A-881757 provides a key understanding of the HSE abundance in the KREEP-free lunar mantle, while the regolith breccia meteorites Y-86032, Y 981031, and Y 983885 offer us to examine the nature, flux, and composition of the materials striking the unexplored lunar surface away from the PKT. Most importantly, these results will provide a robust constraint on the HSE abundance of the Moon, globally.

Let’s slip into inspiral

Date: 2024-04-05
Speaker: Dr. Shilpa Kastha
Venue: Online ---> https://imeet.vconsol.com/join/1736146599?be_auth=NzM2NDU3

Abstract

I will start with a brief introduction to gravitational waves and update about the current detections and my involvement in those. My main focus will be a state-of-the-art discussion on contemporary tests of general relativity with gravitational wave observations and my contributions to developing a few of those.

Optical Monitoring of a long-period dynamically new comet C/2020 V2 (ZTF)

Date: 2024-04-04
Speaker: Goldy Ahuja
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Comets are the pristine bodies that retain the essential information of the early Solar System. They are mainly placed in two reservoirs, i.e., Kuiper Belt and Oort Cloud. These reservoirs hold a large number of comets. The comets in the Kuiper belt are responsible for the short-period low-inclination known as Jupiter family comets (JFC), while comets in the Oort Cloud account for the long-period comets with different inclinations (as compared to the JFC). Studying the composition of different classes of comets is essential to understanding the formation and evolution of the Solar System. Dynamically New Comet (DNC) is a subcategory of long-period comets with a semi-major axis > 10000 AU. These comets are entering the inner Solar System for the first time, which gives us an excellent opportunity to study their composition. The Zwicky Transient Facility discovered Comet C/2020 V2 (ZTF) in November 2020. It was categorized as a dynamically new comet. In the talk, I will present the different results of this dynamically new comet C/2020 V2 (ZTF) using the photometric observations from TRAPPIST and spectroscopic observations from different observatories in India.

A geochemical study on the Kali River with emphasis on chemical weathering and anthropogenic impacts, south-western India

Date: 2024-04-02
Speaker: Dr. Arun Kumar
Venue: Online

Abstract

Small mountainous rivers (SMRs) in tropical regions are some of the most active sites for chemical weathering and associated CO2 consumption. Studies have revealed the incredibly high rates of chemical weathering in these areas. Geochemical sampling on the Kali River Basin (KRB) revealed that silicate weathering is the major contributor to cation yields, while carbonate weathering has a minor impact. These rates are among the highest reported for granitic-gneiss terrains in SMRs, emphasizing the importance of studying geochemical processes. The pollution effects on the riverine ecosystem are assessed by examining chemical and biological components. The findings of this study have important implications for environmental management and for the development of effective strategies to mitigate human activities' adverse impacts on riverine chemistry and the ecological health of the river and coastal areas.

Gaining insight into radiative and variability phenomena of black hole X-ray binaries

Date: 2024-04-02
Speaker: Nazma Husain
Venue: online: https://meet.google.com/jqv-rbwg-unz

Abstract

Around 72 Black Hole X-ray Binary (BHXB) candidates have been discovered till now, showcasing variety of radiative phenomena and rapid variability in the X-ray lightcurve. This variability manifests itself as Quasi-Periodic Oscillations (QPOs) and broadband noise continuum in the power spectra. These properties offer a unique lens to study extreme gravitational environments in close regions to the black hole. Despite substantial research, our understanding of the origin and energy-dependent behaviour of the variability remains incomplete. I will focus on the modelling of variability, testing its different origins and exploring the spectral behaviour in different accretion regimes, using data from AstroSat, NICER, NuSTAR and Swift. In addition, I will discuss a peculiar case of a highly luminous BHXB, which exhibited non-standard disk behaviour. I will conclude by exploring future prospects to better our understanding of the accretion physics around different compact object systems.

Long-term X-ray temporal and spectral study of a Seyfert galaxy Mrk 6

Date: 2024-03-28
Speaker: Narendranath Layek
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Active galactic nuclei (AGNs) are the extremely luminous and most persistent energetic sources in the universe, powered by mass accretion onto the supermassive black hole (SMBH) at the centre of its host galaxy. The X-ray emission from AGN is vital to probe the physical processes in extreme gravity as it is thought to originate from a high-temperature electron cloud called the corona or Compton cloud, situated near the black hole. We present a long-term X-ray study of a nearby Active Galactic Nucleus Mrk 6, utilizing observations from XMM-Newton, Suzaku, Swift and NuSTAR observatories, spanning 22 years from 2001 to 2022. Mrk 6 is a relatively unexplored AGN that has exhibited “changing-look” behaviour in optical observations. However, its characteristics in the X-ray band have not been thoroughly investigated. We found a complex correlation between the soft (0.5 − 3.0 keV) and hard (3.0 − 10.0 keV) X-ray light curves. This result prompts a detailed investigation through spectral analysis, employing various phenomenological and physical models on the X-ray spectra. Based on the overall result obtained from X-ray spectroscopy, we found that, although Mrk 6 displays characteristics of a changing-look AGN (CLAGN) from optical observations, our X-ray spectral analysis did not show any significant variation in the X-ray luminosity and Eddington ratio over a period of 22 years. This indicates that in the X-ray regime, the source did not show any change in its behaviour during the observational period. In this talk, I will discuss our findings from temporal and spectral studies of Mrk 6, obtained from the analysis of X-ray data.

Investigating water-rock interaction on Martian crust using nakhlite meteorites

Date: 2024-03-22
Speaker: Mr. Aditya Das
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

A hint toward how water-rock interaction occurred on the Martian crust is provided by the Nakhlites due to the clay deposition along the fractures of primary minerals. To gain further insight into the water-rock interaction, multiple Nakhlite meteorites have been obtained throughout the established depth profile to determine whether the alteration of the primary mineral is uniform in all the Nakhlites or varies along the depth profile.

Radiative Fermion Masses and Strong CP

Date: 2024-03-22
Speaker: Mr. Gurucharan Mohanta
Venue: Room.No:469 (Main Campus)

Abstract

The hierarchical structure of the Standard Model (SM) charged fermions can be explained by the mechanism of radiative generation of fermion masses. In this mechanism, third-generation fermions are allowed tree-level masses, and lighter fermion masses are induced through loops. Implementation of such mechanisms requires extensions of SM. We will discuss a scenario that can possibly generate fermion masses radiatively and possesses a solution to Strong CP.

Towards the discovery and characterisation of Earth analogs with the PLATO mission

Date: 2024-03-21
Speaker: Dr. Alexandre SANTERNE
Venue: Google Meet: https://meet.google.com/wsj-jvrj-ipw

Abstract

PLATO is a mission from the European Space Agency that will be launch in 2026. It aims at discovering and characterising transiting exoplanets, down to Earth-size planets in the habitable zone of their host star (so called, the Earth analogs). Unlike the Kepler mission, the ground-based characterisation of the planet’s mass is fully part of the mission objective and ground-segment design. During this seminar, I will present the PLATO mission, including the most recent news about its development. I will also details what are the plan for the radial-velocity follow-up of the PLATO candidates and the discuss the current limitations.

Implications of very light sterile neutrinos for absolute mass variables

Date: 2024-03-21
Speaker: Mr. Debashis Pachhar
Venue: Room.no: 469 (Main Campus)

Abstract

The framework of three-flavor neutrino oscillation is a well-established phenomenon, but results from the short-baseline experiments, such as the Liquid Scintillator Neutrino Detector (LSND) and MiniBooster Neutrino Experiment (MiniBooNE), hint at the potential existence of an additional neutrino state characterized by a mass-squared difference of approximately 1 eV². The new neutrino state is devoid of Standard Model (SM) interactions, commonly referred to as the “sterile neutrino” state. In addition, a sterile neutrino with a mass-squared difference of 10^{-2} eV² has been proposed to improve the tension between the results obtained from the Tokai to Kamioka (T2K) and the NuMI Off-axis ν_e Appearance (NOνA) experiments. The hypothesis of an additional light sterile neutrino state introduces four distinct mass spectra. In this talk, we discuss the implications of the above scenarios for the observables that depend on absolute mass of the neutrinos, namely - the sum of neutrino masses (∑) from cosmology, the effective mass of the electron neutrino from beta decay (mβ), and the effective Majorana mass ( mββ) from neutrinoless double beta decay. We show that, some scenarios can be disfavored by the current constraints of the above variables.

Influence of solar wind medium on the propagation of Earth impacting Coronal Mass Ejections in Heliosphere

Date: 2024-03-20
Speaker: Mr. Sandeep Kumar
Venue: USO Seminar Hall

Abstract

Coronal Mass Ejections (CMEs) are subject to changes in their direction of propagation, tilt, and other properties. We investigated 15 Earth-impacting coronal mass ejections (CME) observed during April 2010 to August 2018 in the Heliospheric Imager (Onboard STEREO) field of view (FOV) to study their propagation in the heliosphere. Out of 15 events, approximately 50 % followed self-similar expansion up to approximately 40 R⊙. Only two events showed significant rotation in HI FOV. The rest of 50 % events showed deflection either in latitude or longitude. This study suggests that CME rotation is not very common in the heliosphere. Our study emphasizes the importance of considering both the ambient magnetic field and solar wind environment to understand the heliospheric propagation of CMEs. The observed deflections and rotations of CMEs can be attributed to a combination of factors, including their interaction with the ambient solar wind, the influence of the ambient magnetic field, and the favorable conditions in the heliosphere required for rotation. These findings contribute to our understanding of the complex dynamics involved in CME propagation and highlight the need for comprehensive modeling and observational studies to improve space weather predictions.

A Multi-wavelength Study of Magnetic Cataclysmic Variables

Date: 2024-03-20
Speaker: Nikita Rawat
Venue: Google Meet: https://meet.google.com/nzs-gife-xpb

Abstract

Magnetic Cataclysmic Variables (MCVs) are a class of semi-detached binary star systems that consist of a white dwarf (WD) and a companion star, typically a Roche-lobe filling late-type main sequence star. The strong magnetic field associated with the WD distinguishes MCVs from other cataclysmic variables. It plays a crucial role in governing the accretion process in these binaries and also decides two distinct classes of MCVs: polars and intermediate polars (IPs). In polars, the magnetic field of the WD is strong enough (typically, in a range of 10-100 MG) to lock the whole system into synchronous (or almost synchronous) rotation. On the other hand, IPs have a weaker magnetic field (<10 MG) due to which they rotate asynchronously. The majority of IPs have the spin period of the WD, roughly one-tenth of the orbital period of the binary system. MCVs exhibit a wide range of timing (periodic and quasi-periodic) and spectral properties, more commonly in optical and X-ray wavelengths. These characteristics serve as valuable tools for unravelling and gaining insights into the intricate accretion processes within these systems. Among the MCVs, the appropriate classification of new sources is also essential to understand these systems thoroughly in terms of their accretion geometry. Further, the variable nature of accretion flow is one of the basic characteristics of an IP and has been observed in only a few IPs. In this talk, I will discuss the various photometric, spectroscopic, and polarimetric characteristics of a diverse sample of such objects in various evolutionary stages with spin-to-orbital period ratios ranging from 0.1 to 1.0 to gain insights into the various accretion flow scenarios these systems manifest.

Geochemical behaviour and cycling of Uranium and Molybdenum in the Ganga (Hooghly) river estuary, India

Date: 2024-03-19
Speaker: Dr. Rakesh
Venue: Online

Abstract

The study forms a detailed investigation of sources and processes involved in the geochemical cycling of selected redox-sensitive elements (U and Mo) in the estuary of the Ganga (Hooghly) River. Being dominated by monsoonal climate and characterized by large suspended sediment load, the Hooghly River estuary (HRE) provides an opportunity to study the impact of variable water discharge and suspended sediment concentration on the nature and magnitude of elemental cycling via solute-particle interaction in the estuarine mixing zone. We have investigated the chemical compositions of the (i) river/estuary water samples, (ii) coexisting suspended particulate matter (SPM), (iii) bed sediments, (iv) exchangeable phases of the sediments, (v) estuarine core sediments, and (vi) urban and industrial effluent waters. Specifically, we seek to determine if the estuary acts as a source or sink for these elements or if they behave perfectly conservatively. Investigation of the coexisting dissolved and solid phases allows us to evaluate the nature and intensity of solid-solution interaction processes in modifying the dissolved distributions of U and Mo. Using data of the dissolved, bulk SPM and its exchangeable phases in the mass balance calculations, it is evaluated whether the excesses (or deficit) of dissolved U and Mo are sustained by their complementary loss from (or gain onto) the suspended particulate matter. Furthermore, the role of tidally-induced resuspended sediments and suboxic diagenesis in the sediment column is brought out through the compositions of the bottom and core sediments. The data of industrial and urban effluents are utilized to assess the role of anthropogenic source(s) in supplying U and Mo. Finally, we evaluate the magnitude of modification of riverine dissolved fluxes of these elements due to the estuarine processes.

Probing the Hidden Universe: Direct and Indirect Searches of Dark Matter

Date: 2024-03-19
Speaker: Dr. Divya Sachdeva
Venue: Online ---> https://imeet.vconsol.com/join/9022656493?be_auth=NTAzNzE4

Abstract

Recent years have seen strong support for dark matter (DM) from observations on a multitude of scales, with a range of experiments operational, approved, or proposed to explore DM theories across various masses. The vastness of the parameter space of DM necessitates exploring model-dependent and model-independent approaches while investigating the symbiosis between astrophysical observations and particle physics experiments. In this talk, I will highlight my past and present research projects where we obtained limits on parameter space of various DM candidates and outline future research plans. I will conclude with a discussion on two key areas of my research plan: a) the impact of potential interaction of DM with Standard Model (SM) in altering its velocity distribution and expanding the detectable parameter space for direct detection experiments; and b) the presence of non-relativistic DM near supermassive black holes, which can lead to high-density DM regions that produce robust annihilation signals, thereby enhancing our indirect search capabilities.

Exploring the interplay of gravity, magnetic field, and turbulence at the hub of a Giant molecular cloud G148.24+00.41

Date: 2024-03-19
Speaker: Vineet Rawat
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

he relative importance of magnetic fields, turbulence, and gravity in the early phases of star formation is still not well understood. The plane of sky component of the magnetic field can be traced indirectly using the dust polarization of background starlight. In a recent work, we report the first high-resolution dust polarization observations at 850 μm around the most massive clump, located at the hub of the Giant Molecular Cloud G148.24+00.41, using SCUBA-2/POL-2 at the James Clerk Maxwell Telescope. In this talk, I will discuss the relative orientations of intensity gradients and local gravity with the magnetic field, which shows a dominant role of gravity in driving the gas collapse as the magnetic field orientations and gravity vectors seem to point towards the dense clumps. A better correlation of intensity gradients with the B-fields tells that matter is following the B-field lines or vice-versa. Our observation has resolved the massive clump into multiple substructures. We study the magnetic field properties of two regions, central clump (CC) and northeastern elongated structure (NES). Using the modified Davis–Chandrasekhar–Fermi method, we determine their magnetic field strengths to be around ∼24.0 ± 6.0 μG and 20.0 ± 5.0 μG, respectively. I will present the analysis done over CC and NES regions to understand their localized magnetic field-to-gravity ratio, magnetic criticality, Alfvénic state, and overall energy budget.

Hearing the Universe Hum with Gravitational Waves and Primordial Black Holes at Pulsar Timing Array: astrophysical, cosmological and particle physics interpretations

Date: 2024-03-18
Speaker: Dr. Anish Ghoshal
Venue: Room no: 469 (Main Campus)

Abstract

We will discuss interpretation of the nHz stochastic gravitational wave background (SGWB) seen by NANOGrav and other Pulsar Timing Array (PTA) Collaborations in the context of supermassive black hole (SMBH) binaries. The frequency spectrum of this stochastic background is predicted more precisely than its amplitude. We will discuss how Dark Matter friction can suppress the spectrum around nHz frequencies, where it is measured, allowing robust and significant bounds on the Dark Matter density, which, in turn, controls indirect detection signals from galactic centers. Next we will discuss alternative cosmological interpretations including cosmic strings, phase transitions, domain walls, primordial fluctuations and axion-like physics each of which may lead to Primordial Black Hole formation. Focussing on primordial black holes (PBHs) production in various cosmological scenarios involving single-field inflation, multiple fields, particularly the Curvaton model, as well as those based on the presence of remnants dominated by the false vacuum and show the PBH formation from these remnants including the contribution from the false vacuum and the bubble walls, during strong first-order phase transition by estimating the collapse using the hoop conjecture. Such PBH formations have associated Gravitational Waves from bubble collisions, the spectral shape of which is distinct from that of scalar-induced GW. Finally we will end by putting these comparative studies to test via We will discuss how well these different hypotheses fit the NANOGrav data, both in isolation and in combination with SMBH binaries, and address the questions: which interpretations fit the data best, and which are disfavoured. Finally we also discuss experimental signatures that can help discriminate between different sources of the PTA GW signals with complementary probes using CMB experiments and searches for light particles in DUNE, IceCUBE-Gen2, neutrinoless double beta decay, and forward physics facilities at the LHC like FASER nu, etc. along with Primordial Black Hole formation and its constraints.

Volcanism along the rings of the crisium basin on the moon date

Date: 2024-03-15
Speaker: Ms. Neha Panwar
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The Crisium Basin (17.0 °N, 59.1 °E) is a ~1100 km multi-ring basin formed at ~4.07Ga hosting widespread volcanism within its central depression and along its rings. The results from Luna 24 and remote sensing observations suggest that the basalts of the Mare Crisium have been emplaced between 3.45 to 2.52 Ga. The basalts from the Inner Depression display a range of composition as indicated by their TiO2 abundances that vary from 6-10 wt.% in the east to <2 wt.% in the west. The sub-surface units exposed by larger craters are also compositionally distinct from Mare Crisium basalts, thereby revealing the possibility that the composition of the basalts evolved with time. However, there has been no comprehensive study regarding the composition and emplacement timescales of the basalts along rings of the Crisium Basin. The basalts along the rings of the Crisium Basin have been emplaced within Mare Undarum, Mare Spumans, Mare Anguis, Cleomedes Crater and Lacus Bonitatis. My recent study identified Marginis West as an episode of volcanism along the outermost ring of the Crisium Basin. This study, for the first time, examines the compositional diversity and ages of the basalts emplaced along the rings of the Crisium Basin to better understand its geological evolution. In the seminar, the results will be discussed.

Umbral flashes and their possible association with running penumbral waves

Date: 2024-03-14
Speaker: Mr. Sandeep Dubey
Venue: USO Seminar Hall

Abstract

Sunspots ; being magnetic hotspots ; play a vital role in governing dynamics of the solar atmosphere. Umbral flashes are one of the most dynamic phenomena observed in the sunspot umbral chromosphere. Flashes are observed as small scale intensity enhancements having an approximate periodicity of 3 minutes, interpreted as manifestation of shock developed due to steepening of slow mode waves. Slow mode waves with frequencies above acoustic cutoff frequency get channeled to higher layers of atmosphere along inclined magnetic field lines. Another interesting wave phenomenon observed in sunspot penumbra are running penumbral waves (RPW), appearing as concentric dark and bright rings of disturbances propagating from the umbra-penumbra boundary to edge of penumbra, with a periodicity of 5 minutes approximately. RPWs are also considered as slow mode waves propagating along inclined magnetic fields. In this division seminar; I shall discuss results obtained by analyzing spectroscopic observations of umbral flashes in Ca II 8452 Å line; recorded by narrow-band imager working with the Multi-Application Solar Telescope (MAST). I shall also discuss the aspect of association of running penumbral waves with umbral flashes.

X-ray and Optical Studies of the Be/X-ray Binary IGR J06074+2205

Date: 2024-03-14
Speaker: Birendra Chhotaray
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

X-ray binaries are bright X-ray sources consisting of a compact object (white dwarf, neutron star, and black hole) and a main-sequence star as its companion. The compact object emits X-rays by accreting mass from the companion star, which is bright in optical. High-mass X-ray binaries (HMXBs) are one type in which the companion is a massive (M >10 M⊙, O or B spectral type) main-sequence star. In the Be/X-ray binary, a subtype of HMXB, a compact object (mostly neutron star) accretes mass from the circumstellar disc of its Be companion. We aim to understand the X-ray and optical properties of the Be/X-ray binary IGR J06074+2205. We have analyzed the X-ray data obtained from NuSTAR and NICER observatories to investigate the properties of the neutron star and optical data from MIRO and HCT to probe the properties of the Be companion. In this talk, I will discuss the time and luminosity-dependent properties of the Be/X-ray binary, which is obtained by timing and spectra analysis of X-ray and optical data.

Changing-State AGNs: Challenging our Understanding of AGNs

Date: 2024-03-13
Speaker: Dr. Arghajit
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Changing-state active galactic nuclei (CSAGNs) show the appearance and disappearance of broad emission lines in their UV/optical spectra on timescales of months to decades. The CSAGNs can not be explained by standard unified model AGNs that successfully explain all AGN phenomena in the last four decades. Here, we will discuss our current understanding of CSAGNs. We will also discuss open questions and future prospects.

Large Submarine Groundwater Discharge from Karnataka Coast, Southwestern India: Quantification, Influencing Factors, and Ecological Implications

Date: 2024-03-12
Speaker: Dr. Lino Yovan
Venue: NanoSims Hall

Abstract

Submarine groundwater discharge (SGD) contributes a notable portion, ranging from 6-12%, of the total freshwater inputs to the global ocean and has immense implications in coastal zone management. In my presentation. I will discuss our study focused on delineating the SGD dynamics along the Karnataka coast, specifically its flow into the Arabian Sea. Employing subsurface seepage meters, the first of their kind, we quantified the fluxes of carbon, nutrients, and trace metals associated with SGD. Our findings reveal that the estimated SGD rates in this locale surpass those reported elsewhere globally, with the productivity of the coastal aquifer and monsoonal precipitation identified as primary influencers of SGD discharge mechanisms. By employing subsurface seepage meters, we achieved precise estimations of seepage rates, without the influence of tides and waves that traditional seepage meters face. Additionally, we observed that SGD flow dynamics are linked to inland hydraulic gradients and tidal fluctuations, along with the extensive coastal deposits. These findings emphasize the need for proactive coastal ecosystem conservation, especially amid escalating climate change and human activities.

Understanding the innermost geometry of accreting Seyfert galaxies using X-ray reverberation techniques

Date: 2024-03-11
Speaker: Dr. Mayukh Pahari
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Signs such as rapid X-ray fluctuations and significant variability in RMS values imply that the X-ray emitting source in an accreting black hole system is nearest to the black hole. However, details regarding its size, shape, and precise position remain unclear, often linked to the base of the radio jet along the black hole's vertical spin axis. X-ray reverberation, a vital observation technique involving coronal X-rays reflecting off the inner accretion disc, indicates a delayed, modified emission. Interestingly, the time delay measurements from such a modified emission in UV and optical follow standard thin disc theory; however, X-ray departs. In this talk, I will discuss how X-ray reverberation observationally differs from other wavelengths and how the lamppost geometric configurations can be used to explain the measured X-ray reverberations in Seyfert galaxies.

Hub-filament systems as progenitors of star cluster formation

Date: 2024-02-29
Speaker: Dr. M. S. Nanda Kumar
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

All stellar clusters form in hub-filament systems (HFS) and massive stars form in the hubs. The HFS structure is essentially that of what is generally referred to as molecular clouds (few to few tens of parsec) and hubs represent the central gravitating clump (1 pc) within HFS. I will first review our present knowledge of HFS and discuss how it can explain known properties of stellar clusters. Next, I will present our ongoing work to explore the star-gas relationship in the MonR2 HFS to understand whether molecular clouds are long lived resulting in slow star formation or vice versa. I will conclude by discussing the latest notions of how galaxies convert the interstellar medium (ISM) into stars and maintain the ISM life-cycle.

Deglacial evolution in ventilation of the western equatorial Atlantic Ocean and its link to atmospheric CO2 changes

Date: 2024-02-27
Speaker: Dr. Partha Jena
Venue: NanoSims Hall

Abstract

The marine and atmospheric carbon pools are strongly linked to one another and the air-sea gas exchange processes considerably control the atmospheric CO2 budget. In this regard, Radiocarbon provides unique insights into the air-sea exchange and the Ocean’s ability to sequester atmospheric CO2. We combine results from Radiocarbon measurements of foraminifera specimens and intermediate complexity numerical model simulations to understand the role of the Atlantic Ocean and Atlantic Meridional Overturning Circulation (AMOC) in driving atmospheric CO2 changes. We reconstruct a ‘Radiocarbon ventilation age’ record from the intermediate depth western equatorial Atlantic (WEA) Ocean, which acts as a gateway for CO2 trapped in North Atlantic Deep Water (NADW) before getting released to the atmosphere in the Southern Ocean. The model simulation highlights a near-complete shutdown of AMOC during Heinrich Stadial (HS)-1, resulting in a poorly ventilated Atlantic Ocean that aligns well with the high B-P ventilation ages at our study site. On the contrary, the Atlantic Ocean was properly ventilated during North Atlantic interstadials i.e., the Holocene and the Bølling–Allerød (BA) resulting in low B-P ventilation ages. The high resolution (resolved at every 150 years) Radiocarbon ventilation age record focuses on the deglaciation period (~18 to 12 ka BP) during which multiple short-term (~200 years) CO2 overshoot events have been observed amid a steady CO2 rise. Concurrent with the CO2 overshoot events, we observe prominent ventilation age drops in WEA intermediate depths. A strong coupling between AMOC strength, atmospheric CO2 and North Atlantic temperature is observed during the 14.8 ka and the 11.7 ka events. On the contrary, in the case of the 16.3 ka event, the rise in atmospheric CO2 was not directly associated with AMOC strength. Nevertheless, it is plausible that the Southern Ocean remained a significant source of atmospheric CO2 during that period. In this presentation, our findings underlining the important role played by the Atlantic Ocean and AMOC in deglacial carbon cycle changes will be discussed.

Heliospheric Propagation of Coronal Mass Ejections

Date: 2024-02-27
Speaker: Sandeep Kumar
Venue: Online:https://meet.google.com/uue-rpmm-upb

Abstract

Coronal Mass Ejections (CMEs) represent explosive releases of solar plasma and magnetic fields into the heliosphere, exerting significant influence on interplanetary space weather. The dynamics of CMEs involve the eruption of vast amounts of solar material and magnetic energy, driven by complex processes within the solar corona. As these charged particles are ejected into the heliosphere, they interact with the ambient medium. Upon arriving at the Earth they create disturbances that can affect the Earth's magnetosphere, ionosphere, and geomagnetic field. Understanding the initiation and propagation of CMEs is crucial for predicting their potential impact on space-based technologies, communication systems, and power grids. In this talk, I will discuss various factors affecting heliospheric propagations of coronal mass ejections and consequently how this interaction of the CMEs with the ambient medium can affect its impact on the Earth.

The Gorkov-Teitelbaum thermal activation model for the cuprates

Date: 2024-02-27
Speaker: Prof. Navinder Singh
Venue: Room no: 469 (Main Campus)

Abstract

A brief overview of this very successful phenomenological model for the pseudogapped state of cuprates will be presented. A recent work on the pseudogapped state on a related system (Strontium Iridate) using this model will be discussed.

Reprocessing of pvo radio occultation data from 1978-1982 date

Date: 2024-02-23
Speaker: Prof Martin Pätzold, Director, Riu-Planetary Research At Cologne
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

RIU-Planetary Research has secured funding support for the reprocessing and interpretation of the Pioneer Venus Orbiter (PVO) radio science experiment ORO original raw open-loop occultation data recorded between 1979 and 1982. A limited selection of original ORO profiles, primarily comprising electron density profiles, with only a few temperature profiles, was obtained from an NSSDC server and published by Withers(2020) on a Boston University server. To achieve our goals, we are utilizing state-of-the-art software code along with an updated version of the Venus gravity field and newly processed PVO orbit data provided as SPICE kernels. I shall present atmospheric and ionospheric profiles derived from S-band and differential Doppler recordings, respectively, processed from the original Pioneer Venus Orbiter raw open-loop data sets. We will then compare these profiles with VEX-VeRa radio occultation profiles obtained under comparable observation conditions, as well as with the few existing original PVO profiles retrieved from the Boston University server account (Withers, 2020).

Forces and dynamics involved in evolution of IDP in solar system date

Date: 2024-02-16
Speaker: Ms. Aanchal Sahu
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Dust is the major constituent of Solar System objects which is present everywhere in the Interplanetary Space. These dust particles are originated by diverse sources such as Asteroid Belt, Kuiper Belt, Oort Cloud, and residual debris left since the formation of the Solar System. Occasionally, comets traversing from outside of Solar System are expected to bring volatiles and leave dust particles due to sublimation. Larger particles tend to migrate inward, while smaller ones are swept outward. When hypervelocity dust encounters Earth's atmosphere, it ablates, forming a metallic ion layer. On the Moon, these particles impact the surface directly, ejecting material that may escape lunar gravity. These dust particles play a vital role in various observed phenomenon such as Zodiacal Light and Meteor Showers. During their inward motion towards the Sun, they encounter a complex interplay of gravitational and non-gravitational forces like Poynting-Robertson Drag, Radiation Force, Solar Wind Force, and Lorentz Force depending upon the size and position of the particles in Inner Solar System. These forces dictate the dynamics of the particles, leading to changes in their orbital elements. The capture and trapping of dust particles near a planet can be understood by the solution of N-body integration formulation. In my discussion, I will present the flux of Asteroidal and Cometary Dust within the Inner Solar System. Additionally, I will delve into the forces and how they shape orbital elements, leading to evolution of IDP. Further, I'll share its connection to my ongoing research work.

Timekeepers in Earth Sciences: Application of U-Pb geochronology to earth and planetary processes

Date: 2024-02-13
Speaker: Dr. Amal Dev J
Venue: NanoSims Hall

Abstract

The application of insitu analytical techniques has garnered substantial attention in the past decades owing to its increasing potential in resolving many fundamental problems in earth and planetary processes. Recent advancements in the application of texturally controlled laser ablation (LA) ICPMS analysis of accessory mineral phases in rocks have added significantly to the petrochronological studies owing to their high spatial resolution, fast data acquisition, improved precision-accuracy, and cost-effectiveness. The insitu LA-ICPMS studies have been highly explored to unravel the geodynamic evolution of sedimentary basins; timing, nature, and duration of crust forming and crust recycling events; tectonothermal evolution of polydeformed terranes and isotopic characteristics of planetesimal bodies etc. This is in conjunction with the fact that individual accessory phases in the samples can fingerprint discrete events due to their variable response to physio-chemical conditions. Among the different isotopic systematics, the application of insitu U-Pb geochronology combined with relevant isotopic information has been widely recognized as the most robust tool to gain insights into these processes. Some relevant applications of U-Pb geochronometry along with specific case studies will be addressed in the talk with future prospects.

Soft gluon non-factorizable charm loops in B to K(*) l+l- and implications for new physics

Date: 2024-02-13
Speaker: Prof. Namit Mahajan
Venue: Room no: 469 (Main Campus)

Abstract

I'll discuss some recent progress on computing the non-factorizable soft gluon contribution to B to K(*) l+l- decays arising from charm loops. These constitute a considerable hadronic uncertainty when comparing with the experimental data. Some implications for new physics in these modes will be discussed.

Understanding the Impact of Coronal Mass Ejections on Space Weather: Integrating Observations and Modelling

Date: 2024-02-12
Speaker: Dr. Ranadeep Sarkar
Venue: USO Seminar Hall

Abstract

Coronal mass ejections (CMEs), the most violent eruptive phenomena occurring in the heliosphere, are recognized as one of the major sources for space weather disturbances. CMEs erupt in the form of gigantic clouds of magnetized plasma from the Sun and can reach Earth within several hours to days. If the magnetic field inside an Earth-directed CME or its associated sheath region has a southward-directed north-south magnetic field component (Bz), then it interacts effectively with the Earth’s magnetosphere, leading to severe geomagnetic storms. Therefore, it is crucial to predict the strength and direction of Bz inside Earth-impacting interplanetary CMEs (ICMEs) in order to forecast their geo-effectiveness. Since the magnetic field of solar eruptions cannot reliably be measured via remote means, and direct continuous measurements of the Earth impacting solar transients are routinely available only very close to our planet, modelling of CME magnetic properties is paramount. In this talk, I will present a space weather modelling framework using both analytical and global MHD approaches that could prove to be an operation space weather forecasting tool to predict the geo-effectiveness of CMEs. This talk will also showcase the utilisation of multi-wavelength remote-sensing observations as well as multi-spacecraft in-situ observations at different heliocentric distances to constrain the space weather forecasting models. Further, I will discuss how data obtained from India's space-based solar observatory, Aditya L1 will play a crucial role to enhance our understanding on the CME initiation mechanism.

Extreme Indian Monsoon states lead to oceanic productivity collapses

Date: 2024-02-07
Speaker: Dr. Kaustubh Thirumalai

Abstract

Indian summer monsoon (ISM) hydrology fuels biogeochemical cycling across South Asia and the Indian Ocean, exerting a first-order control on food security in Earth's most densely-populated areas. Despite projected ISM intensification under greenhouse forcing, large uncertainty surrounds future Indian Ocean stratification and primary production -- processes key to the health of already vulnerable fisheries in the region. Here, we present centennially-resolved records of ISM runoff and marine biogeochemical fluctuations in the Bay of Bengal (BoB) since the Last Glacial Maximum (LGM; ~21 ka). We find that ISM runoff was at its weakest during Heinrich Stadial 1 (HS1; 17.5-15.5 ka) and that peak freshwater discharge occurred during the early Holocene (EH; 10-9 ka). Counterintuitively, our records indicate that BoB productivity collapsed during both extreme states of peak monsoon intensity (EH) and failure (HS1). Using individual foraminiferal analyses (IFA) we demonstrate that both extremes were associated with upper-ocean stratification; whereas thermally-mediated stratification suppressed mixing and nutrient-delivery during HS1, outflow-induced stratification driven by strengthened ISM runoff curtailed productivity during the EH. In contrast to the latest Earth-system model projections, our paleoceanographic results raise the possibility of future deterioration in BoB productivity under strengthening monsoon seasonality.

Linking lepton number violation with supersymmetry breaking

Date: 2024-02-07
Speaker: Dr. Ketan M. Patel
Venue: Room no: 469 (Main campus)

Abstract

Supersymmetry and lepton number violation are apparently distinct hypothetical phenomena introduced to address two very fundamental issues of the Standard Model of particle physics: the gauge hierarchy problem and neutrino masses, respectively. In this talk, I will highlight how these phenomena can be linked. Consequences for direct searches, in terms of displaced vertex signatures, shall also be outlined.

Multi-line Spectropolarimetry: Our Key to Understand the Solar Atmosphere

Date: 2024-02-06
Speaker: Dr. Rahul Yadav
Venue: USO Seminar Hall

Abstract

Multi-wavelength observations from various telescopes reveal frequent heating and eruptive events in the solar atmosphere, such as Ellerman bombs, UV bursts, jets, surges, and flares. These events not only heat the lower atmosphere (the chromosphere and transition region) but also impact the dynamics of the corona. Despite decades of study, predicting these events and understanding their detailed mechanisms throughout the solar atmosphere remains unclear. Multi-line spectropolarimetric observations spanning different layers of the solar atmosphere are crucial for understanding various aspects of heating events. In this talk, I will discuss how such observations can be used to construct an observationally driven model of heating events using state-of-the-art multi-line inversion methods. Additionally, I will present recent results from the analysis of multi-line spectropolarimetric observations of a C4-class flare observed with the Daniel K. Inouye Solar Telescope. Finally, I will explore the potential for investigating heating events through coordinated observations from the MAST, IRIS, and Aditya-L1 telescopes.

Insights into the abrupt climatic events (ACE) of Holocene: A paleoclimate conundrum

Date: 2024-01-30
Speaker: Dr. Upasana Swaroop Banerjee
Venue: NanoSims Hall

Abstract

The Indian Summer Monsoon (ISM) plays a pivotal role in the socio-economics of the Indian subcontinent and global climate system. The recent anomalous behaviour of ISM invigorates the need to address spatio-temporal changes of ISM during the ongoing interglacial period, the Holocene Epoch (~11.8 ka- Present). The Holocene has been characterised by various Abrupt Climatic Events (ACE) such as 8.2 ka, 4.2 ka, Bond events, Little Ice Age, etc., based on colossal studies from high latitude regions. Most of these ACEs have been recognised in global natural proxies, however, ISM being a major part of the global climate system, remains poorly understood in terms of its response towards the ACE of the Holocene. Further, the association of the Indian monsoon system with natural forcing and climate variables have remained elusive. In the present talk, a synoptic assessment of Indian monsoon variability and its response towards globally established ACEs will be discussed.

CARMENES: exoearths from Spain

Date: 2024-01-25
Speaker: Dr. José A. Caballero
Venue: Online: https://meet.google.com/fwp-cnit-rko

Abstract

Calar Alto high-resolution search for M dwarfs with Exoearths with Near-infrared and optical Échelle Spectrographs (CARMENES). In other words, it is a "machine for discovering planets like our Earth around the closest stars to our Sun". CARMENES took six years from a concept to the start of operations, and a couple more years of initial data collection until the first science publication, but now is revolutionising our knowledge on exoplanets and their stars in our immediate vicinity. In my talk I will describe what CARMENES is: (i) an ultra-stabilised two-channel spectrograph at an almost dedicated 3.5 m telescope in southern Spain that covers in high spectral resolution and without big gaps from 0.52 μm to 1.71 μm; (ii) a science project aimed at comprehensively searching for and studying planetary systems with nearby, bright, M-dwarf hosts, but that also investigates transiting planets around other stars; and (iii) the German-Spanish consortium that designed and built the instrument and that has operated it under guaranteed and legacy time observations.

Detecting tidal deformation and decay

Date: 2024-01-18
Speaker: Dr. Susana Barros
Venue: online : https://meet.google.com/myq-ynxh-zrk

Abstract

Tidal forces between short-period planets and their host stars are extreme. These lead to the deformation of the planet and the shrinkage of the planet’s orbit. Using the new ESA mission CHEOPS we are attempting to measure both these effects for a sample of exoplanets. Measuring the tidal deformation of the planet would allow us to estimate the second degree fluid Love number and gain insight into the planet's internal structure. Measuring the tidal decay timescale would allow us to estimate the stellar tidal quality factor, which is key to constraining stellar physics. WASP-103 was our first target since it had the largest estimated signature of the tidal deformation. I will present the first detection of the tidal deformation of a planet directly from its light curve. This allowed us to measure the Love number of WASP-103b. I will also present our measurements of the tidal decay of a few targets including WASP-103b and explore our future perspectives.

Cosmic Ray Transport in Magnetohydrodynamic Turbulence

Date: 2024-01-17
Speaker: Dr. Kiritkumar Makwana
Venue: Seminar Room # 113/114 (Thaltej campus)

Abstract

Cosmic rays are affected by magnetic fields as they travel across the universe. Because of the turbulent and chaotic magnetic field lines in the intergalactic and interstellar medium and the heliosphere, cosmic rays are deflected and can exhibit random motion. It is essential, then, to understand how these cosmic rays diffuse out of a particular region of interest, carrying energy, mass, and momentum along with them. This diffusion process depends on the structure of the magnetic field lines in magnetohydrodynamic (MHD) turbulence. I will describe numerical simulations of this diffusion process using test particles in MHD turbulence simulation data. We investigate diffusion at both small and large scales (compared to the gyro-radius). At large scales we get normal diffusion whereas at small scales we observe Richardson diffusion, which is a type of super-diffusion. Different MHD wave modes are decomposed and diffusion due to them individually is also studied. The scaling of the diffusion coefficients with Alfven Mach number is calculated and roughly matches theoretical expectations. It is shown that the fast magnetosonic modes dominate in the cosmic ray diffusion process.

Rheology of the lower crust and its implications for geodynamic studies

Date: 2024-01-16
Speaker: Dr. Sagar Masuti
Venue: NanoSims Hall

Abstract

Postseismic relaxation from large earthquakes and postglacial rebound from the melting of ice sheets induce transient deformation of the solid Earth, particularly in the deep crust and upper mantle. The melting of large ice sheets due to climate change further results in sea-level rise, which is of great societal concern. The deformation of the lower crust is mainly controlled by feldspar. The mechanical properties of feldspar at steady-state are well constrained. However, the physical mechanism underlying transient creep, an evolutionary, hardening phase converging to a steady state asymptotically, is still poorly understood. In order to constrain flow law parameters for the transient creep of feldspar, we performed constant strain rate deformation experiments on synthetic fine-grained anorthite (Ca end member of feldspar) aggregates under wet conditions using a Paterson-type gas deformation apparatus. We analysed the starting and deformed samples in optical microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). We constrain the mechanical data using a Burgers assembly with a thermally activated nonlinear stress versus strain-rate relationship for the dashpots. I will discuss the inferred flow law parameters of the transient creep and demonstrate their importance by using these parameters to study the postseismic deformation following the 2016 Mw 7.0 Kumamoto earthquake.

Exploring the Dark Sector: New Regimes, New Ideas

Date: 2024-01-15
Speaker: Dr. Anirban Das
Venue: Online---> https://bluejeans.com/613207389/4345

Abstract

The overwhelming evidence from astrophysical and cosmological observations have established the existence of dark matter in our Universe. Even though we know that it forms most of the matter, we do not know anything about its nature. Decades of experiments have not yielded any conclusive detection yet. So it is high time to look beyond the simplest models, and broaden the search for nonstandard theories of particle dark matter and cosmology. In the first part of my talk, I will describe a couple of new proposals to use novel materials to look for light sub-GeV dark matter. In the second part, I will briefly describe the nonstandard cosmology of self-interacting neutrinos, how the latest data from Planck and ACT affect the model, and the current status of its link to the Hubble tension.

Lunar south polar landing site characterization from de Gerlache to Shackleton ridge region

Date: 2024-01-12
Speaker: Ms. Sachana A S
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The Moon has gained significant scientific and exploration values after the detection of volatile species of diverse nature by recent lunar missions. The lunar poles with presence of permanently shaded regions (PSRs) serve as a natural laboratory for understanding processes work on cold traps of lunar poles. Near future lunar explorations majorly focused on detailed mapping and quantification of water ice exposures using rovers, on surface and subsurface levels. Here, I present a case study of four potential landing sites on the ridge connecting de-Gerlache and Shackleton craters, all situated within the expansive South-Pole Aitken (SPA) basin, by integrating information from recent lunar missions. The South Pole emerges as a unique and compelling area for exploration, promising insights into the compositional and structural diversity and chronological aspects of the basin also hosting several potential PSR’s. I will discuss detailed characterisation of these sites based on terrain characteristics, which include slope, illumination, surface roughness, surface temperature, geomorphology, accessibility to nearby PSRs, compositional diversity, and trafficability.

Probing the habitability conditions for the Earth-like exoplanets by their atmosphere characterization

Date: 2024-01-11
Speaker: Manika Singla
Venue: Online Mode: https://meet.google.com/meg-tqis-hzu

Abstract

In this talk, I will discuss about the ways to probe the habitability conditions on Earth-like exoplanets which lie in their host-star’s habitable zone as these exoplanets are the potential candidates for the habitability. We modelled the atmospheres of the Earth-like exoplanets by computing their reflection spectra, transmission spectra and the polarization phase curves. We also computed this for nine known Earth-like exoplanets (including Proxima Centauri b and Trappist-1e), which orbit around stars of spectral types G, K and M and estimated their maximum values of Bond Albedo. For this purpose, we assumed certain initial conditions on the atmospheric Temperature-Pressure profiles and the atmospheric chemical compositions and used the opacity data to solve the radiative transfer equations. I will further discuss about this in detail during the talk. Finally, I will discuss the profound effects of various surface compositions of the planet, clouds, orbital inclination angle, presence of biomolecules like H2O, CH4, O3, etc. on the reflection, transmission and the polarization of the planet. I will conclude the talk by discussing how our work will greatly enrich the upcoming search for the habitable exoplanets using big telescopes like HabEx, ARIEL, HWO, TMT, etc.

Making and collapse of mountain belts: Insights from petrography, thermodynamic modelling and diffusion kinetics

Date: 2024-01-09
Speaker: Dr. Nilanjana Sorcar
Venue: NanoSims Hall

Abstract

Metamorphism, partial melting in conjunction with uplift of the deep crustal rocks are integral part of mountain building process or orogenesis. Recognizing such crustal processes has an important bearing on geodynamics as it provides the information on the tectono-thermal history of the crust. Petrography, thermodynamic modelling and diffusion kinetics are key approaches in decoding metamorphic, cooling and exhumation (upliftment) history of a mountain / orogenic belt by simulating different temperature and pressure conditions of metamorphism over time as well as cooling/exhumation rate of the deep crustal rocks. New analytical capabilities, in particular, the development of the electron micro-probe, played an enabling role by providing the means of analyzing small volumes of materials in different textural settings in intact rock samples which is crucial to develop thermodynamic and diffusion modelling in such study. In this talk, I will address the nature of tectonometamorphic evolution of young and active as well as ancient mountain belt from India and East Antarctica to show how crustal rocks evolve through geological time in different P-T regime. The development of improved methods of diffusion kinetics using compositional zoning of mineral (e.g. garnet) in combination with petrologically constrained paths of thermal evolution will be highlighted to gain insights into the nature of cooling of high- grade metamorphic rocks, as well as into the tectonic evolution of an orogenic belt (e.g. Himalayas, Eastern Ghats Belt etc.). Finally, I will talk about my future research direction using the integrated studies of mineralogy, thermodynamic modelling and diffusion kinetics to the field of Planetary Sciences, for example, to the domain of shock metamorphism and mineralogical studies of other planetary rocks.

Space weather effects on venusian ionosphere

Date: 2024-01-05
Speaker: Mr. Satyandra M. Sharma
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The Venusian ionosphere is influenced by solar activity and solar cycle variations, changing its characteristics, including V2 and V1 morphology, photoelectron production rates, and electron density. Solar events such as flares and solar energetic particles (SEPs) induce significant enhancements in electron density, altering the ionosphere's chemical composition. The radio occultation experiment provides an important tool to study the ionospheric characteristics. I will present the current understanding of the Venusian ionosphere under different space weather conditions and give a brief detail on the methodology that I will use to study the responses, to both average and extreme space weather components.

Probing the magnetic field and gas kinematics in the IRDC G11.11-0.12, Galactic "Snake"

Date: 2024-01-04
Speaker: Omkar Jadhav
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Numerous observational investigations have demonstrated that Infrared Dark Clouds (IRDCs) are important sites for studying the birth of embedded protostars including massive stars. IRDCs appear as absorption features against the galactic background in mid-infrared images. Magnetic fields are thought to play a crucial role in the mass accretion and stability of IRDCs. However, the exact role of magnetic fields in the early stages of star formation remains unclear. My present work focuses on the Galactic ‘Snake’ IRDC G11.11-0.12, which is known to host early phases of star formation activities. We have studied the plane of the sky magnetic field derived using the emission polarization and gas kinematics toward the entire IRDC. The existing JWST near-infrared images reveal signatures of star formation, which are new findings and has not been reported in existing literature. In this talk, I will present several new results about the Galactic "Snake" in more detail.

Observations and modelling of coronal mass ejections to understand their space weather effect

Date: 2024-01-04
Speaker: Dr. Ranadeep Sarkar
Venue: USO Seminar Hall

Abstract

Coronal mass ejections (CMEs) are one of the major sources for space weather disturbances. If the magnetic field inside an Earth-directed CME or its associated sheath region has a southward-directed north-south magnetic field component (Bz), then it interacts effectively with the Earth’s magnetosphere, leading to severe geomagnetic storms. Therefore, it is crucial to predict the strength and direction of Bz inside Earth-impacting interplanetary CMEs (ICMEs) in order to forecast their geo-effectiveness. Since the magnetic field of solar eruptions cannot reliably be measured via remote means, and direct continuous measurements of the Earth impacting solar transients are routinely available only very close to our planet, modelling of magnetic properties is paramount. In addition to forecasting the strength of Bz, another significant challenge in space weather prediction involves accurately estimating the arrival time of ICMEs. An in-depth understanding of the initiation mechanism of CMEs is crucial for enhancing our ability to provide extended lead times in predicting when ICMEs will reach Earth. In this talk, I will highlight how data obtained from India's space-based solar observatory, Aditya L1 will play a crucial role to enhance our understanding on the CME initiation mechanism. This talk will also showcase the utilisation of Aditya-L1 data in conjunction with the resources of existing space-based observatories as assets for space weather forecasting. In particular, a space weather forecasting framework will be presented using both analytical and global MHD approaches. Further, I will discuss a recently developed flux-rope model implementation to the global MHD models that could prove to be a major step-forward in forecasting the geo-effectiveness of CMEs.

Isotopic composition of atmospheric water vapour: recent observations and future potentials

Date: 2024-01-02
Speaker: Prof. M. G. Yadava
Venue: NanoSims Hall

Abstract

Water vapour is a good tracer of atmospheric circulation. The isotopic composition of atmospheric moisture (δ18O and δD) can provide unique constraints on how water is transported, mixed, and changes phase and is thus a valuable tool in the study of the Earth’s hydrologic cycle and for improved understanding of paleoclimate proxies. We have recently started looking into the dynamics of ambient water vapour using stable isotopes as a primary tool. With the adaptation of the laser spectroscopy method for measuring ambient air-water isotopic composition, studies on atmospheric vapour at a temporal resolution of ~100 seconds are possible and are becoming significant topics in understanding hydrological perturbations on daily to seasonal scales. Current measurements, complexities in the method, and future applicability will be discussed.

2023

Stability and mobility of lunar water-ice: current understanding through thermophysical modelling

Date: 2023-12-29
Speaker: Ms. Ambily G
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Lunar poles have been confirmed as the regions where water-ice can be stable for long periods of time. The temperatures and thermophysical environment of these areas make them favorable to cold-trap volatiles and are potential sites for future lunar missions. The surface ice will be transported to subsurface through various mechanisms, depending on the temperature and regolith characteristics. Knowledge about these processes will help us targeting more accessible and resourceful sites in future. In this talk, I will discuss the present understanding of stability and transport of water-ice through thermophysical modelling studies, and explore how the illumination conditions change the surface temperatures on the Moon.

Survey of Bare Active Galactic Nuclei in the Local Universe (z < 0.2): On the Origin of Soft Excess

Date: 2023-12-28
Speaker: Prantik Nandi
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Active Galactic Nuclei (AGNs), a subclass of Super-Massive Black Holes (SMBHs) emit radiation across the electromagnetic spectrum. The extreme luminosity of the AGNs arises from the accretion of matter onto the Super Massive Black Holes (SMBHs), forming an accretion disk that generates thermal photons. In the X-ray range, the inverse Compton scattering of these photons by the electron cloud, the Compton cloud, produces a power-law spectrum. Therefore, X-ray observations provide detailed insights into the inner accretion disk and Compton cloud in details. The soft excess, an excess emission below 2 keV, is an extraordinary feature in the X-ray spectra for most Seyfert 1 AGNs. The origin of soft excess is one of the major open questions in AGN research. Initially thought to be blackbody radiation, the high disk temperature corresponding to soft excess emission contradicts standard theories. some cases suggest that the reflection or Comptonization could be the origin of soft excess, But these theories are unable to explain all cases. These discoveries provoked the alternate origins of the soft excess. A recent study by Nandi et al. (2023) explores the origin of the soft excess for a sample of 21 Seyfert 1 AGNs with ‘bare’ nuclei. Long-term X-ray (0.5-10.0 keV) observations from observatories like XMM-Newton and Swift/XRT reveal a strong correlation between the luminosities of the primary continuum (3.0-10.0 keV) and soft excess (0.5-2.0 keV) across the sample. From this study, we conclude that the observed correlation between the soft excess and primary continuum luminosities could have originated due to inverse Compton scattering in the Compton cloud, and both the luminosities depend on the accretion rate only.

Protoplanetary Disks: Disk Dynamics and the Distribution Of Volatiles

Date: 2023-12-22
Speaker: Mr. Soumik Kar
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

A protoplanetary disk is a rotating circumstellar disk composed of dense gas and dust around a recently formed young star. Understanding its evolution is essential to understanding planet formation and the origins of our solar system. Volatiles, encompassing a diverse array of compounds such as water, carbon dioxide, and complex organic molecules, significantly impact the composition and characteristics of growing planetary bodies. Here, we will discuss the basic properties of disks, such as mass, radius, surface density, etc, from both observations and numerical models. It will help us understand the complex dynamics that shape the overall structure of protoplanetary disks and influence the spatial distribution of volatiles. Additionally, we investigate the radial temperature profiles of these disks, probing the thermal conditions that drive volatile transport and chemical reactions. We plan to develop a model in which the physical and chemical processes governing volatile distribution in protoplanetary disks are crucial model components. This study plans to provide a foundation for understanding the diverse range of volatile-rich environments in the protoplanetary disks.

Study of short GRBs and their afterglows

Date: 2023-12-21
Speaker: Ashish Kumar Mandal
Venue: Seminar Room # 113/114 (Thaltej campus)

Abstract

Gamma-ray bursts (GRBs) are brief intense flashes of gamma-rays produced at cosmological distances. They are classified as short or long based on the bimodality of the observed duration distribution of their prompt gamma-ray emission. This empirical classification was based on hypotheses that two classes have different progenitors. Long GRBs (LGRBs) have been firmly connected to the collapse of massive stars through the detection of associated Type Ibc core-collapse supernovae. But support for the connection between short GRBs (SGRBs) and merger of binary neutron stars (BNSs) or NS-BH binaries came from indirect observational evidence, population synthesis studies, and numerical simulations. The joint detection of gravitational wave GW170817 and a SGRB (GRB170817A) on 17th August 2017 from a BNS merger confirms that BNSs are progenitors of (at least some) SGRBs. This SGRB was 2 orders of magnitude nearer and 2 to 6 orders of magnitude less energetic than SGRBs with known distances. If it were at least 30% fainter, then most of our curent GRB detectors might have missed this event. In this seminar I will discuss on the properties of prompt gamma-ray emission, early afterglow in soft X-ray, UV, optical and late afterglow in IR, radio of SGRBs, some findings which support GRB classification criterion, and highlight sensitivity of few GRB detectors.

Multi-band Polarimetric Study towards the Cluster NGC 7380

Date: 2023-12-19
Speaker: Dr. Sadhana Singh
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The polarimetric study is an effective tool for providing information about the magnetic field orientation and will also reveal information about the properties of interstellar dust grains and their alignment. The polarization of background starlight through the interstellar medium is a result of the dichroic extinction of starlight through the aligned grains. In the seminar, I will present the multi-band polarimetric study of the open star cluster NGC 7380. Polarimetric observations are carried out in four filters using an ARIES imaging polarimeter from a 104-cm telescope of ARIES. The orientation of dust grains in the line of sight is found to be parallel with the Galactic magnetic field. Towards the east and southeast regions, the dust structure appears much denser than in other regions and is also reflected in the polarization distribution. Three groups of stars are identified in the Stokes plane, which suggests the presence of an additional weak magnetic field component. Additional results from the polarimetric analysis will be presented e.g. size distribution, polarizing efficiency, and foreground dust distribution. I will show the overall distribution of polarization and position angle towards Galactic anti-center direction and lastly, I will discuss future plans.

Study Of Whisler Waves And Other Plasma Waves In Venusian Ionosphere

Date: 2023-12-15
Speaker: Ms. Aarti Yadav
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The ionosphere of Venus is the uppermost layer of the atmosphere where significant numbers of free thermal electrons and ions are present. The base of Venusian ionosphere is situated around an altitude of 120 km and the layer can go up to 300 km or more than that which is remarkably affected by solar activity. I shall discuss the profound influence of solar activity on the ionospheric regions. The discussion extends to Venus' induced magnetosphere, exploring the mechanisms governing its generation and shedding light on the properties of plasma within this unique planetary environment. One focus point will be the Whistler waves around Venus, their characteristics and the significance in the Venusian ionosphere. Recent findings regarding whistler waves near Venus also will be presented and I shall outline my future research direction with whistler waves around Venus

Multi-instrument studies of solar flares and energetic particles

Date: 2023-12-14
Speaker: Dr. Frederic Schuller and Mr. Malte Victor Philipp Broese
Venue: USO Seminar Hall

Abstract

SPECULOOS: Hunting exoplanets of ultracool dwarfs with 1-meter ground-based telescopes network

Date: 2023-12-14
Speaker: Dr. Sebastián Zúñiga-Fernández
Venue: Online Mode : https://meet.google.com/vnm-saoz-izz

Abstract

The SPECULOOS (Search for habitable Planets EClipsing ULtra-cOOl Stars) project aims to perform a transit search on the nearest (< 40 pc) ultracool (<3000K) dwarf stars. The project is based on a network of 1m robotic telescopes, composed by the four ones of the SPECULOOS-Southern Observatory (SSO) in Cerro Paranal, Chile, one telescope of the SPECULOOS-Northern Observatory (SNO) in Tenerife, and the SAINTEx telescope in San Pedro Martir, Mexico. The prototype survey of the SPECULOOS project on the 60 cm TRAPPIST telescope (Chile) discovered the TRAPPIST-1 system, composed of seven temperate Earth-sized planets orbiting a nearby (12 pc) Jupiter-sized star. The project's main motivation is to discover potentially habitable planets well-suited for detailed atmospheric characterisation with upcoming giant telescopes, like the James Webb Space Telescope (JWST) and European Large Telescope (ELT). The SPECULOOS target list contains a homogeneous selected sample of close-by low-mass and ultracool stars.The targets have been selected as low-mass dwarfs starting from the Gaia DR2 catalogue, which has been cross-matched with the 2MASS point-source catalogue. Beside conducting observations of targets from the SPECULOOS input catalog, a fraction of the available observing time of the SPECULOOS network is used to carry out different science goals, the so-called annex programmes. A large annex programme is the support of space based transit search surveys such as K2 and TESS through the follow-up of transit candidates of late-type dwarfs.The upcoming Gaia DR3 release will largely improve the parallaxes and colours for the 40 pc sample, thus encompassing more targets that were excluded in our original target list. In these talks we are going to present our observation strategy, management of our archive and scientific products. We will discuss the first results of the survey and the synergy of our programs with the Transiting Exoplanet Survey Satellite (TESS) and JWST.

Isotopic Constraints On The Accretion And Early Evolution Of Earth Date

Date: 2023-12-14
Speaker: Dr Nikitha Susan Saji, Central State University, Wilberforce,Ohio, USA
Venue: Online

Abstract

There exists abundant evidence today, from meteorites and their components, for the presence of planetary-scale isotope anomalies of nucleosynthetic origin in the solar system. The observed isotopic variations testify to the differential incorporation of presolar dust grains synthesized in multiple stellar environments by accreting planets and planetesimals, although the exact mechanism behind their peculiar distribution in the solar protoplanetary disk is highly debated. Nevertheless, they carry important information about protoplanetary disk structure and dynamics, as well as the history of formation of terrestrial planets such as Earth and Mars. In this talk, I will review the extent and possible causes of nucleosynthetic isotope heterogeneity evident in solar system materials, with an emphasis on multi-element isotope variability trends in relation to neodymium. The goal is to disentangle the relative role of disk processing and heterogeneous infall in delineating the multitude of nucleosynthetic variability trends observed in solar system materials. I will also discuss how an accurate determination of the nucleosynthetic makeup of material precursors of terrestrial planets remain important towards the robust application of short-lived radioactive decay chronometers to study early planetary differentiation and subsequent geochemical evolution.

A Tale of Two Spicules

Date: 2023-12-13
Speaker: Mr. Ravi Chaurasiya
Venue: USO Seminar Hall

Abstract

Spicules are the thin, elongated, hair-like features seen through a high-resolution telescope in chromospheric spectral lines such as H-alpha and Ca II lines. These spicules move upward and downward in the solar atmosphere with velocities ranging between 20 and 150 km/sec. They are believed to carry a mass flux several times greater than that of the solar wind. In this seminar, I will briefly discuss the history and initial development of the spicules and how type II spicules were discovered along the flows associated with these type II spicules in the solar atmosphere.

Astronomy in Africa for Achieving the Sustainable Development Goals

Date: 2023-12-13
Speaker: Dr. Mirjana Pović
Venue: Online Mode : Google Meet Link : https://meet.google.com/nec-gqmd-tuq

Abstract

Education and its contribution to science, technology and innovation are the key points to combat poverty in the long term. Education is also a key point to empower girls and women, which is fundamental to achieve the United Nations Sustainable Development Goals (SDGs). Astronomy is a powerful tool to promote education and science but, in addition, it is also one of the leading sciences to bring strong technological developments and innovation. Africa has an amazing potential due to its natural and human resources for scientific research in astronomy. The situation of astronomy and space science in Africa has changed significantly in recent years, becoming emerging fields across the continent, and never before has it been as possible to use astronomy for development as it is today. This talk will first summarize the current status of astronomy developments in Africa. Secondly, using as an example different activities carried out for the development of education, science and technology in Ethiopia, East Africa and across the continent, it will show how through these we can fight poverty in the long term and increase in the future our chances of achieving the UN Sustainable Development Goals (SDGs) for the benefit of our whole society.

Lunar dark mantle deposits: role of pyroclastics in understanding Explosive volcanism

Date: 2023-12-08
Speaker: Mr. Dibyendu Misra
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Dark Mantle Deposits (DMD) constitute a distinct lunar lithological unit, primarily associated with the floor fractures of major mare-filled basins. These deposits have morphological characteristics of smooth homogeneous texture with relatively low albedo. DMDs are distinguishable from exogenic dark hallows mainly from morphological characteristics of non-circular shape, diffused boundaries, and alignment with volcanic features. DMDs contain pyroclasts in the form of partially crystallized droplets of Fe-bearing glasses that provide insights into explosive lunar volcanic eruptions and reveal the presence of volatile-enriched mantle resources. These pyroclastic deposits are further categorized into local and regional deposits based on their areal extent. Local pyroclastics are attributed to vulcanian-type volcanic activity whereas regional deposits are associated with strombolian or fire-fountain-type volcanism. The physical and compositional variations within local and regional DMDs contribute to a comprehensive understanding of the primary lunar mantle composition and evolutionary process of the Moon. The remote identification of volcanic glasses is challenging due to spectral overlap with lunar Fe-bearing minerals in the visible to near-infrared range. The high spatial resolution Moon Mineralogy Mapper global data coverage is used in this work to develop a methodology that can be used for the identification and characterization of localized and regional DMDs.The extensive study carried out at a few local and regional deposits will be presented and discussed.

Evidence of late irradiation from calcium aluminium-rich inclusions date

Date: 2023-12-01
Speaker: Mr. Advait Prasad Unnithan
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Isotopic studies of meteorites exhumed excesses in specific isotope(s) of element(s), which were demonstrated to have originated from the decay of radionuclide(s). The Genesis of these parental short-lived now-extinct radionuclides (SLNs), having half-life in the range of a few days to millions of years, has been a subject of research investigation for decades. Several astronomical, observational, theoretical, and isotopic studies of meteorites suggest that our Sun, during its infancy (4.56 Ga years ago), was very active, resulting in several episodes of intense flaring with copious production of enhanced solar energetic particles. These solar energetic particles (SEPs), on interaction with ambient gas and dust in the early Solar system, can produce SLNs such as 7Be (t1/2=53 days), 36Cl (t1/2=0.3Ma), 26Al (t1/2=0.72Ma), 10Be (t1/2=1.38Ma), etc. These isotopes generated in the late stage (>5 Ma after the birth) irradiation events can get incorporated in the early solar system solids forming larger bodies, asteroids, planetesimals, etc. This late irradiation event is hypothesized to make a small but significant contribution to a few of these SLNs. Calcium-Aluminium rich Inclusions (CAIs), being one the first forming solids in the Solar system, are important suites of objects to understand the earliest history of solar system events and processes. Sodalite (Na8Al6Si6O24Cl2) and Wadalite (Ca6Al5Si2O16Cl3), chlorine (Cl) bearing metasomatically generated secondary minerals found in some CAIs have been studied for traces of SLN 36Cl.

Precision in Motion: Fabry-Perot Etalon as a Wavelength Calibrator for Extreme Precision Radial Velocity Methods

Date: 2023-11-30
Speaker: Shubhendra Nath Das
Venue: Seminar Room # 113/114 (Thaltej campus)

Abstract

In this talk, I will explore how the Fabry-Perot etalon is changing the game in making radial velocity measurements super precise. I will start by understanding why it's crucial to calibrate wavelengths and look at the qualities a good calibrator should have. I'll show you how the Fabry-Perot etalon meets these standards, comparing it with other methods and pointing out its amazing benefits. At the end I will wrap up by discussing the stability and instrumental needs of the Fabry-Perot etalon to meet expectations.

Phase Shift Measurement of Acoustic Waves in the Lower Solar Atmosphere

Date: 2023-11-24
Speaker: Dr. Hirdesh Kumar
Venue: USO Seminar Hall

Abstract

Solar atmosphere provides a conducive environment for the generation, propagation, mode-conversion, and dissipation of various magnetohydrodynamics (MHD) waves. Acoustic waves are generated by compressibility, whereas the buoyancy-restoring force generates gravity waves. The acoustic waves generated inside the Sun's convection zone are trapped in the acoustic cavities and form standing waves. In the quiet-Sun photosphere, the cutoff frequency is 5.2 mHz, and low-frequency acoustic waves are evanescent. Utilizing the near-simultaneous photospheric and chromospheric line-scan observations in Fe I 6173 A and Ca II 8542 A, respectively, obtained from the Narrow Band Imager instrument installed with the Multi-Application Solar Telescope operational at USO, we have estimated seven height velocities within the Fe I line and nine height velocities within the Ca II line using the bisector method. The analysis of phase shift vs frequency and height shows a non-zero phase shift, indicating the non-evanescent nature of low-frequency acoustic waves in the quiet-Sun. In this talk, I will discuss the possible factors responsible for the non-evanescent nature of low-frequency acoustic waves.

Spectro-polarimetric Studies of Symbiotic Binaries

Date: 2023-11-23
Speaker: Arijit Maiti
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Symbiotic stars are binary systems consisting of a red giant and a hot radiation source, usually a white dwarf. The cool giant star loses material via Roche lobe overflow or through its stellar wind, which flows onto the hot compact star, usually via an accretion disk. Symbiotic binaries are of particular interest to astronomers as they can be used to learn about stellar evolution. They are also vital in the study of stellar wind, ionized nebulae, and accretion because of the unique interstellar dynamics present within the system. However, not a great deal is known about the structure and dynamics of such systems. Spectro-polarimetric studies of such systems represent an excellent technique for probing their 3D morphology and internal dynamics. Of particular interest are the spectro-polarimetric studies of the two broad Raman scattered lines at 6825 and 7082 angstroms seen in the spectra of most symbiotic stars. In this talk, I shall discuss the basics of symbiotic star systems, their properties, and how spectro-polarimetric techniques help in probing such systems with particular emphasis on the diagnostic potential of the Raman scattering process. I shall conclude the talk by discussing how ProtoPol (a prototype spectro-polarimeter currently under development in PRL) with a medium resolution of (R ~ 7000) can help conduct such spectro-polarimetric studies.

Evolution of X-ray Instrumentation and Astronomy

Date: 2023-11-10
Speaker: Neeraj Tiwari
Venue: Seminar Room # 113/114 (Thaltej campus)

Abstract

X-ray astronomy, a latecomer in the field of observational astronomy, remained unexplored until the 1960s due to the inherent challenge of cosmic X-rays being unable to penetrate Earth's atmosphere. Since its inception, X-ray astronomy has undergone a remarkable evolution, reshaping our understanding of the cosmos. It began its journey with experimental X-ray observations using sounding rockets, then progressed to balloon-borne missions, and eventually to the deployment of advanced satellite-based observatories. This evolutionary path has illuminated the field of astronomy, revealing complex high-energy phenomena associated with black holes, neutron stars, and active galactic nuclei. X-ray astronomy has played a vital role in understanding the mysteries of accretion processes, supernovae, X-ray binaries, and gamma-ray bursts. It has also provided crucial insights into the formation and evolution of galaxies, the behavior of matter under extreme conditions, and the dynamics of celestial collisions. The pursuit of precision and clarity in X-ray observations was made possible through the evolution of technology over the last six decades, which led to the development of groundbreaking X-ray telescopes like Chandra, XMM-Newton, and NuStar. These missions owe their success and improved performance to the advancements in technology, enabling us to address long-standing questions within the field of astronomy. In this seminar, we will journey through the evolution of X-ray astronomy, exploring its inspiring history and the ways it has deepened our understanding of high-energy astrophysical processes. We will also explore the ongoing challenges in the development of the next generation of X-ray telescopes and the promising opportunities they hold for the future of this captivating branch of astronomy.

VLT/HiRISE: Direct characterization of young giant exoplanets at high spectral resolution

Date: 2023-11-09
Speaker: Dr. Arthur Vigan
Venue: Online link : https://meet.google.com/mhu-ukug-gyy

Abstract

A major endeavor of this decade is the direct characterization of young giant exoplanets at high spectral resolution to determine the composition of their atmosphere and infer their formation processes and evolution. Such a goal represents a major challenge owing to their small angular separation and luminosity contrast with respect to their parent stars. Instead of designing and implementing completely new facilities, it has been proposed to leverage the capabilities of existing instruments that offer either high contrast imaging or high dispersion spectroscopy, by coupling them using optical fibers. In this seminar I present the implementation and first on-sky results of the HiRISE instrument at the very large telescope (VLT), which combines the exoplanet imager SPHERE with the recently upgraded high resolution spectrograph CRIRES using single-mode fibers. The goal of HiRISE is to enable the characterization of known companions in the H band, at a spectral resolution of the order of R = 100 000, in a few hours of observing time. I will present the science case, the main design choices and the technical implementation of the system, and the first performance assessment after commissioning.

Use of Bose symmetry to test symmetry violations

Date: 2023-11-06
Speaker: Prof. Rahul Sinha
Venue: Room no: 469 (Main campus)

Abstract

We will show how Bose symmetry in heavy flavour decays can be used to study violations of CP, CPT and SU(3) symmetries

X-Ray Spectral Properties of Narrow Line Seyfert 1 galaxy

Date: 2023-11-02
Speaker: Ms. Isha Mahuvakar
Venue: Seminar Room # 113/114 (Thaltej campus)

Abstract

Narrow-line Seyfert 1 (NLS1) galaxies are a subclass of Active Galactic Nuclei (AGN), showing relatively narrow width (FWHM < 2000 km s-1) of broad permitted emission lines in their optical spectra. These galaxies are supposedly powered with low mass supermassive black holes (105 – 107 Msun) and exhibit high accretion rates. In this seminar I shall present X-ray spectral properties of a NLS1 galaxy B3 1702+457 using multi-epoch XMM-Newton and AstroSAT observations. Our preliminary results show that the 0.3-10 keV X-ray spectra of this NLS1 can be fitted with an absorbed power law plus reflection component and Fe Ka emission line. We also find the evidence for absorption edges at soft energies. The multi-epoch X-ray observations hints for the flux as well as spectral variability. In this talk, I shall emphasize on the peculiarity of NLS1 X-ray spectral properties.

Geodynamic evolution of the Tharsis province Mars: insights from volcano-tectonic and fluvial landforms

Date: 2023-10-27
Speaker: Dr Anil Chavan
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

I will talk about the volcano-tectonic and fluvial landforms of two different areas: Syria planum (south- east) and Koval’sky crater (south) of Tharsis province. The tectonic feature associated with the upwelling of the mantle from Noachian to the early Amazonian time bears distinctive characteristics of local and regional tectonism. New insight into the evolution of volcanic domes and associated fractures may be gained from the analysis of the ages of the tectonic and volcanic features. The number, total length, linear density of faults in the Syrian Planum region, and deformation rates are reported for each of the five stages of tectonism. 1076 Syria planum-related tectonic features, which are radial, tangential, and concentric to the center of the Syria planum, were assigned to one of these stages based on their stratigraphic and crosscutting relationships defined in the most recent geological map. The attribute of each stage indicates that the deformation rate in the early/middle Noachian, late Hesperian and in early Amazonian was lower, while it has acquired a pick in late Noachian to early Hesperian. It also shows well-established fluvial system draining towards north and subsequently went to the Echaus plateau. This study also focuses on the volcano-tectonic landforms on the southern limb of Tharsis province Koval’sky crater, and their interaction with the fluvial activity. Here, we analysed graben system in southern Tharsis province, which affected Koval’sky crater and accommodated a volcanic plug along one of the major graben systems on the eastern part of the impact. The volcanic plug within crater bears evidence of fluvial channels showing radial drainage patterns.

Investigation of Atmospheric Clouds and Boundary Layer over the Western-Indian Region

Date: 2023-10-23
Speaker: Mr. Dharmendra Kumar Kamat
Venue: USO Seminar Hall

Abstract

Atmospheric clouds are crucial in the Earth’s hydrological cycle, radiation budget, and manifest regional and global weather conditions. The formation process of clouds starts in the lowest layer of the atmosphere (known as the Atmospheric Boundary Layer, ABL)and forms at heights ranging from a few hundred meters to several kilometers. Clouds are highly dynamic in space and time, and their proper representation in climate models remains challenging. The true representation of clouds in weather and climate models and a better understanding of physical processes governing cloud formation and dynamics are essential for predicting future climate. This seminar will discuss the cloud processes, cloud-boundary layer interaction, and different techniques for investigating clouds and ABL. Results derived using Lidar observations under the PRL’s Indian Lidar Network (ILIN) Programme over the three western-Indian regions (Ahmedabad, Mount Abu, and Udaipur) will be presented.

Multiwavelength study of hot and exotic stellar populations in star clusters

Date: 2023-10-23
Speaker: Ms. Sharmila Rani
Venue: Online

Abstract

Star clusters are dynamically active stellar systems where interactions and collisions, especially involving binaries, are quite frequent and result in stellar exotica such as blue straggler stars (BSSs), cataclysmic variables, etc. Globular clusters (GCs), being old and dense, host low-mass stars in various stages of evolution, making them ideal for investigating the end stages of low-mass star evolution and the origins of exotic stellar populations, which are not yet fully understood. Ultraviolet (UV) studies conducted so far using HST and GALEX data have revealed the presence of intriguing stars, such as extreme horizontal branch (EHB) and blue hook (BHk) stars in GCs, making them enigmatic systems. Furthermore, the discovery of multiple stellar populations (MSPs) in both types of clusters through UV observations has provided new perspectives on their formation and evolution. We examined the properties of late-stage, UV-bright and exotic stellar populations in targeted star clusters using the multiwavelength data from the ground as well as space-based observatories. We primarily have employed the UV data from the Ultraviolet Imaging Telescope (UVIT)onboard AstroSat, India’s first multi-wavelength observatory, in both far-UV (FUV) and near-UV (NUV) bands. In this talk, I will present an in-depth analysis of four clusters, consisting of two intermediate-mass GCs (NGC1261 and NGC2298) and two open clusters (OCs) (NGC188 and NGC2818). We constructed the UV-optical colour-magnitude diagrams (CMDs) for member stars and compared them with theoretical isochrones to probe the multiple population phenomenon in GCs. Furthermore, based on the atmospheric parameters estimated using the SED fitting technique, we constrained the formation scenarios of the hot horizontal branch (HB) and exotic stars in clusters. Additionally, FUV imaging analysis of a Planetary Nebula (PN) within the field of OC NGC2818 strongly suggests its membership in the cluster, offering a unique opportunity to test stellar evolution models.

How radio techniques can give insights into solar eruptions

Date: 2023-10-20
Speaker: Dr. Anshu Kumari
Venue: USO Seminar Hall

Abstract

The coronal magnetic field (B), the ultimate driver of space weather, plays an essential role in the formation, evolution, and dynamics of the small and large-scale structures in the solar corona. These structures lead to gigantic explosions in the solar atmosphere in the form of large-scale eruptions, such as coronal mass ejections (CMEs), which may severely impact near-Earth space. CMEs are often accompanied by radio emissions, which provide access to observations of the related solar, heliospheric, and ionospheric space weather phenomena. Radio techniques can provide early signatures of particle acceleration associated with solar flares and CMEs. In this seminar, I will talk about state-of-the-art ground and space-based radio instrumentation for solar and space weather studies. Using radio observations and time-dependent data-driven numerical modelling of active regions, I study the formation and eruption of the coronal flux ropes. I will highlight the radio techniques to constrain the initial CME properties close to the Sun and the numerical modelling approach to understand the initiation and evolution of large-scale solar eruptions.

Lunar elemental abundance estimation based on Chandrayaan-2 class and Chandrayaan-1 moon mineralogy mapper datasets

Date: 2023-10-20
Speaker: Dr Megha Upendra Bhatt
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The mapping of refractory elements at local and global scales is an important tool for revealing the petrological characteristics of the Moon and for understanding its geological evolution. The direct approaches (X-ray and Gamma ray spectroscopy) mainly provide elemental abundances at spatial resolution of tens of kilometers. In contrast, the indirect approaches (UV-VIS-NIR spectroscopy) provide spatial resolution of tens to hundreds of meters but they are influenced by space-weathering and topographic effects and majorly based on empirical relationships between band parameters and the chemical composition of returned samples. Chandryaan-2 Large Area Soft X-ray Spectrometer (CLASS) data from Chandrayaan-2 mission as ground truth to estimate major refractory elements for understanding the petrological characteristics of the Moon. The algorithm uses multivariate regression between CLASS derived elemental abundances from selected regions spread over mare and highlands and spectral parameters derived using the nearly global coverage of the Moon obtained by the Moon Mineralogy Mapper (M3). The results will be discussed are based on a comparative analysis considering independent techniques applied on regional and global scales.

An initiative to explore the life beyond Earth at Amity Center of Excellence in Astrobiology

Date: 2023-10-13
Speaker: Dr Sneha Arunkumar Gokani, Ramanujan Fellow, Amity University Maharashtra, Mumbai
Venue: Seminar Room # 113/114 (Thaltej Campus

Abstract

We have been involved in the development of the two biological payloads Amity space biology experiment (ASBE) and the Amity life growth experiment (ALGE). The center has been actively been involved in field exploration studies in the analogues regions of Ladakh by bringing together scientists working in the areas of Astrobiology and space sciences from India and Abroad. The centers explored the surface and subsurface of this regions as well as isolated extremophiles from the above said regions. Amity has also developed a rover Mars Amity Surface Characterization and Operations Trainer (MASCOT-1). This was a prototype and can be used as a platform for setting up of mars exploration instruments. Our center has also collaborated with Berkeley SETI Research Center at University of California Berkeley to conduct India’s first search for advanced extraterrestrial life. The program aims to develop novel tools utilizing state-of-the-art strides made in field-programmable gate arrays for high-speed data capture from existing and upcoming radio telescopes. Our expertise also extends to modeling and simulation of hydrothermal systems, impact craters and planetary analogue studies. With the aim of studying the microgravity effects on plant samples, our students are developing a Random Positioning Machine (RPM). Apart from this, we also work on space weather aspects on Earth specifically; our work focuses on the investigation of geomagnetic changes that take place during transient solar eruptions. We have carried out the statistical study on exploring the possibility of reduced geoeffectiveness of solar cycle 24. In addition to that, studies related to dependence of different solar drivers on the outer radiation belt energetic electron depletion is carried out. The details of the above works will be presented during the seminar.

On the nature of AGN in dust-obscured galaxies

Date: 2023-10-12
Speaker: Abhijit Kayal
Venue: Thaltej Seminar room (113)

Abstract

We explore the nature of Active Galactic Nuclei (AGN) hosted in high-redshift (0.59 <= z <= 4.65) dust-obscured galaxies (DOGs) by performing X-ray spectral study of DOGs detected in the XMM-SERVS deep field. The X-ray spectra fitted with a simple absorbed power law plus reflection component or with a torus-based reflection model reveal that a substantial fraction (30 per cent) of our sample DOGs are heavily obscured (N_H > 1023 cm-2) AGN. The absorption-corrected 2.0 - 10 keV X-ray luminosity suggests them to be luminous quasars. The NH versus Eddington ratio diagnostic plot infers that our DOGs host a heterogeneous population of AGN containing heavily obscured AGN as well as reddened quasars. We find that only a few of our sources are likely to belong to an early phase during which accretion and obscuration peak, while the remaining sources possibly belong to a late phase during which radiative feedback from dominant AGN blows away obscuring material. Since X-ray detection is limited only to bright AGN, we also use deep multi-frequency radio continuum surveys, which help us to unveil a large fraction of low-luminosity AGN hosted in DOGs. In this talk, I shall emphasize the importance of deep radio surveys to uncover the obscured population of AGN.

Interplanetary Coronal Mass Ejections

Date: 2023-10-09
Speaker: Ms. Binal Patel
Venue: USO Seminar Hall

Abstract

Interplanetary coronal mass ejections (ICMEs) are interplanetary manifestations of CMEs. ICMEs are essential to study as they are attributed to various space weather phenomena such as solar energetic particle (SEP) events, interplanetary (IP) shocks, and geomagnetic storms, etc. An interesting subset of ICMEs have enhanced magnetic fields (>10 nT) that rotate slowly through a large angle, low proton temperatures, and low plasma Beta; (ratio of the thermal and magnetic field pressure) are called as magnetic clouds. Magnetic clouds are often termed interplanetary magnetic flux ropes (IMFR). There are clear evidences that magnetic clouds are the drivers of intense geomaganetic storms. Hence, understanding the geometry of the magnetic clouds at 1 AU is crucial for analysing their interaction with Earth’s magnetosphere. In this talk, I will discuss the physical connection between the IMFRs at near-Earth enviornment and corresponding CMEs at the near-Sun region by comparing the magnetic field structures of IMFRs and CME source regions. We attempt to identify the flux rope structure in 18 selected events that occurred during Solar Cycle 24 by fitting models with a cylinder and torus magnetic field geometry, both with a force-free field structure. Our results show that the observed flux rope parameters are well reconstructed with the models. The helicity signs of the magnetic clouds remain conserved during their Sun-Earth transit. Our results further support the idea that a flux rope with the main axis parallel to the PIL erupts in a CME, and the erupted flux rope propagates through the interplanetary space with its orientation maintained and is observed as an IMFR.

IDP in Solar System: Observations, Results and Research Opportunities

Date: 2023-10-06
Speaker: Dr Jayesh P. Pabari
Venue: Seminar Room # 113/114 (Thaltej Campus

Abstract

Interplanetary Dust Particles (IDPs) are found everywhere in solar system. The dust is an important constituent in the formation of solar system. The IDP may originate from sources like Asteroid belt, Kuiper belt and comets. They evolve dynamically in the solar system under the effect of various forces. Though there are some measurements of IDP near Earth and also, in the interplanetary space; the flux and other parameters of IDP at some planets are not understood fully. Further, the dust particles in the solar system may enter a planetary object and affect it in different ways. The speaker will convey observations, results and research opportunities related to IDP in solar system.

Accretion Disk-Corona Connection in Active Galactic Nuclei

Date: 2023-10-05
Speaker: Dr. Indrani Pal
Venue: Online

Abstract

One of the important components of active galactic nuclei (AGN) is the corona, believed to be responsible for the luminous X-ray continuum that is observed in the radio-quiet category AGN. The hot electrons within the corona Compton up scatters the optical and UV photon from the accretion disk to X-ray energies. In spite of the corona being considered an integral part of AGN, much is still unknown about its nature, geometry, location and physical properties. Using data taken from X-ray telescopes such as the NuSTAR and XMM-Newton, a systematic investigation was carried out on the nature of the corona using X-ray spectral techniques. On analysis of a sample of about 100 Seyfert type AGNs, the coronal temperature could be constrained for about 75 AGN. Of these, variation in the temperature of the corona was found in two. Though spectral fits could provide us with important characteristics of the corona, a key unknown is the geometry, which could be constrained using X-ray polarization observations. Using X-ray polarization data from the Imaging X-ray Polarimetry Explorer (IXPE), launched by NASA in December 2021, we could constrain the geometry of the corona in IC 4329A, one among the four radio-quiet AGN for which IXPE observations are available as of today. Details of the results on the coronal properties of AGN obtained from our systematic investigation, as well as plans for the future will be presented.

Chandrayaan-2 XSM: Bits and Bytes to Science Data Archive

Date: 2023-10-04
Speaker: Mithun N. P. S
Venue: Seminar Room # 113/114 (Thaltej campus)

Abstract

Data acquired by various astrophysical observatories are generally made available to the scientific community worldwide often after a short proprietary lock-in period for the instrument team or the proposers of the observations. Such open data policies have played an important role in advancement in our understanding of various astrophysical processes through archival data analysis. While the data policies of ground based observatories differ, almost all space based observatories, which are often fully funded by public money, are required to make the data public with varying lock-in periods. However, the usability of the archival data crucially depends on how well the data archive is prepared and documented. It is also essential to provide the users with analysis tools that apply required corrections and calibration to the observational data which in most cases are quite involved. The Solar X-ray Monitor (XSM) of the Chandrayaan-2 mission has been observing the Sun from lunar orbit and providing measurements of soft X-ray spectra of the Sun for just over four years now. The raw data acquired gets downloaded at designated passes over Indian Deep Space Network (IDSN) at Bylalu, Bangalore. The data then undergoes initial processing at Indian Space Science Data Centre (ISSDC) after which it is made available to the Payload Operations Center (POC) at PRL. Higher levels of data processing and validation are carried out at PRL and the final data archive is hosted at ISSDC PRADAN portal. PRL also maintains an interactive website for users to examine the XSM light curves. This entire chain from data reception to data archival and updating of the website is automated with a suite of software tools that we call as XSMDMS: XSM Data Management System, which in turn uses the XSM Data Analysis Software. In this talk, I will discuss how the XSM data makes its way from bits and bytes to the science data archive.

Investigation of geologically complex chloride-rich terrain on Mars and

Date: 2023-09-29
Speaker: Dr Deepali Singh
Venue: Seminar Room # 113/114 (Thaltej Campus

Abstract

This work involves the exploration of chloride-rich terrains on Mars to understand their origin since their hygroscopic nature enhances their potential to sustain life as compared to other minerals. We aim to reconstruct the geological evolution of one such area and examine the habitability potential of the area when the conditions on Mars became unconducive. In this context, we have investigated a topographic depression within the Terra Sirenum region, one of the largest chloride deposits on Mars. Morphological examination of the area showed that its floor is covered with bright-toned polygons, and while the area near its boundary is rich in Fe/Mg and Al-phyllosilicates, the centre consists of chlorides with a possible mixture of sulfates. The chlorides within the basin were dated back to the Hesperian and imply the weathering of chloride-rich rocks and their transportation to the basin, which gradually desiccated. We have estimated the amount of chloride present and used Einstein's parameter for sediment discharge to determine the duration for which the area was hydrological active. We have further modelled our findings to ascertain the habitability potential of the area.

Contribution of Radio Occultation (RO) Measurements to the Understanding of the Venus Atmosphere

Date: 2023-09-19
Speaker: Dr Janusz Oschlisniok, Rheinish Institute for Environmental Research, Dep. Planetary Research, Cologne, Germany
Venue: Seminar Room # 113/114 (Thaltej Campus

Abstract

In RO measurements a spacecraft which in orbit around Venus sounds the atmosphere of the planet with radio waves. Those are recorded at ground station on Earth. Information about Venus’ atmosphere are achieved from observed changes in the signal phase and amplitude. While the phase shift is used to derive atmospheric profiles of temperature, pressure and number density, the additional variation of the signal power is used to derive the mixing ratios of trace gases like SO2 and H2SO4. Since the derived atmospheric profiles cover the altitude range between about 35 and 80 km altitude, RO measurements provide crucial information to the understanding of the atmospheric state and dynamics.

Mineralogical characterization of hot spring deposits and stromatolites from Martian analog perspective

Date: 2023-09-15
Speaker: Dr Subham Sarkar
Venue: Seminar Room # 113/114 (Thaltej Campus

Abstract

Stromatolites are often regarded as the oldest evidence of life on Earth, and hot springs are thought to be one of the critical locations for the emergence of early life on Earth. Thus, from a Mars science perspective, which has shifted to search for biosignature in recent years, substrates with higher biogenicity have become more relevant for terrestrial-based analog studies. The study includes a thorough examination of terrestrial stromatolites, including their geological background, environmental niche, petrography, mineralogy, and rare earth element geochemistry. The Mesoarchean (>2.5 Ga) Mfolosi Stromatolites of Pongola Supergroup, Kaapvaal Craton, South Africa, are identified as a probable Martian parallel and share similar characteristics to Gusev Crater, Mars. Based on petrography, mineralogy, spectroscopy, and geochemistry, this work discusses the geomorphological context and significance of hydrothermal activity with terrigenous inputs within a peritidal context and thus offers insight into its genesis likely to be relevant in the once existed ocean shore on Mars. Additionally, the hydrothermally-fed Tapovan hot spring in Uttarakhand, India, could be another potential Mars equivalent. This study explored hydrothermal assisted secondary minerals, which include calcium carbonate, Fe-bearing phases, and Fe-/Mg-smectites, similar in line with what was recently detected by Perseverance at the floor of Jezero Crater using advanced spectroscopy and X-ray diffraction techniques. This discovery has significant implications for astrobiological research, providing insights into the putative biosignatures and the paleoenvironmental conditions of Mars, thus assisting in the search for extinct/ extant life on the red planet and beyond.

Introduction to Gamma Ray Bursts (GRBs)

Date: 2023-09-14
Speaker: Ashish Kumar Mandal
Venue: Seminar Room # 113/114 (Thaltej campus)

Abstract

Gamma Ray Bursts (GRBs) are short, intense flashes of gamma rays coming from deep space. They were first discovered (in 1967) by VELA military satellites of the USA launched to govern the 1963 nuclear test-ban treaty. They are observed across the electromagnetic spectrum, from radio to very-high-energy gamma rays. At present, space-based observatories detect, on average, approximately one GRB per day. The extensive observational and theoretical efforts have confirmed them as highly relativistic explosions, confirmed their distance scale, pinpointed their host galaxies, identified the systems that create them and opened them as astrophysical probes throughout the Universe. GRBs are now a major astrophysical tool to probe the final stages of stellar evolution and the creation of supernovae, to examine the creation and propagation of relativistic jets and their impact on the Universe at large, and to use as indicators to identify galaxies across cosmic time-some in the earliest epochs of Universe. The extreme nature of both their progenitors and emission mechanisms makes them the most promising sources for joint electromagnetic and gravitational wave detection. This is demonstrated by the recent (2017) detection of gravitational waves (GW170817) and short GRB (GW170817A) from a merger of the double neutron-star binary system. In this seminar, I will talk about the brief history of GRBs, their observations and properties, different dedicated GRB missions, detection methods, understanding so far, etc., and finally, I will connect you to my work.

Design and development of Venus Orbiter Dust EXperiment (VODEX)

Date: 2023-09-08
Speaker: Sonam Jitarwal
Venue: Seminar Room # 113/114 (Thaltej Campus

Abstract

In the solar system, the interplanetary dust particles (IDPs) originate from the asteroid belt, comets, Kuiper belt and a few other minor sources. During their evolution, they may undergo collision and evaporation or get ejected from the solar system depending on their size and properties. These IDPs are nanometer to micrometer-sized dust particles travelling at hypervelocity, i.e. greater than one km/s. We are developing an Impact Ionization dust detector to study the interplanetary dust particles for future Venus orbiter missions. The signal generated by the dust particle's impact on the detector's target plate is measured, and using its rise time and peak voltage, the particle's physical properties, i.e., mass, velocity and flux, will be derived. In this talk, I will discuss the design, development and testing results of VODEX electronics along with the testing results using a nano-second pulse laser. Also, different types of electronics noise, signal-to-noise ratio calculation, and preliminary thermal analysis results will be discussed.

Intra-night optical variability of radio-quiet narrow-line Seyfert-1 galaxies

Date: 2023-09-04
Speaker: Dr. Vineet Ojha
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Variability studies of Active Galactic Nuclei (AGNs) play a powerful diagnostic tool in understanding the physical processes occurring in objects that are unresolved by direct imaging with currently available techniques. Here, we report the first attempt to systematically characterize intra-night optical variability (INOV) for a sample of seven radio-quiet and/or radio-silent narrow-line Seyfert 1 galaxies (RQNLSy1s) that had shown recurring flaring at 37 GHz in the radio observations at Metsähovi Radio Observatory (MRO), indicating the presence of relativistic jets in them, but no hints of jets in the recent radio observations of Karl G. Jansky Very Large Array (JVLA) at 1.6, 5.2, and 9.0 GHz. A total of 28 intra-night sessions, each lasting > 3 h, was conducted with 1-2.5m class telescopes of ARIES and PRL for the INOV study of this sample. The resulting level of INOV from this sample is found to be statistically comparable to those observed in γ-ray-detected radio-loud NLSy1s (MBH ∼ 10^7 M⊙ ), that display blazar-like INOV. Thus, it appears that even lower-mass (MBH ∼ 10^6 M⊙ ) RQNLSy1 galaxies can maintain blazar-like activities. Furthermore, based on the optical behavior of these seven RQNLSy1s, we infer that INOV from the current sample of RQNLSy1s could be either due to a twisted in-homogeneous jet or magnetic re-connection in the magnetosphere of the black hole. In this talk, I will also discuss the optical study of the most distant gamma-ray-detected NLSy1 (z = 1.344), whose observations were taken from the PRL 2.5m telescope.

Highlights of the sessions from the Asia Oceania Geosciences Society 20th Annual Meeting (AOGS2023)

Date: 2023-09-01
Speaker: Sachana A S, and Ambily G
Venue: Seminar Room # 113/114 (Thaltej Campus

Abstract

The 20th Annual Meeting of the Asia Oceania Geosciences Society (AOGS) was held at Suntec, Singapore, between 30th July and 4th August 2023. In this seminar, we shall be presenting an overview of the discussions carried out during the conference. We shall also discuss the work we presented at the conference.

Comet Observations from the 3.6m Devasthal Optical Telescope (DOT)

Date: 2023-08-31
Speaker: Goldy Ahuja
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

This talk presents the results from the first observations of comets using the ADFOSC (ARIES Devasthal Faint Object Spectrograph and Camera) on the 3.6m Devasthal Optical Telescope (DOT). The famous green comet C/2022 E3 was observed post-perihelion on 16 Feb and 22 Feb 2023. The talk will focus on the challenges faced during the reduction and calibration of the data from the ADFOSC spectrograph. The procedures for reducing the data will be discussed, and the production rate ratio will be presented and compared with results from the TRAPPIST group.

Development of Spectro-polarimeters for PRL Telescopes

Date: 2023-08-28
Speaker: Arijit Maiti
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Polarization measurements in astronomy is one of the most challenging observational techniques given its photon-hungry nature. While imaging polarimetry in broadband filters have been a very successful technique to explore a variety of astro-physical situations, Spectro-polarimetry is rather rare, and not so many instruments available to explore this domain. Spectro-polarimetry is the study of polarization profiles of various features in the spectrum of any astro-physical object. Measuring the wavelength dependence of the polarization of radiation from such sources can reveal valuable and interesting constraints on the nature of objects observed. Here at PRL, we are in the process of developing two such instruments having spectro-polarimetric capabilities. Mt. Abu Faint Object Spectrograph and Camera–Echelle Polarimeter (M-FOSC-EP) is a 2-channel multimode instrument equipped with a low-resolution spectroscopic and imaging arm and an intermediate-resolution (R~15000) spectro-polarimetric arm. As a precursor to this instrument, a prototype spectro-polarimeter called ProtoPol has also been designed, using completely off-the-shelf optical components, for medium-resolution (R~6000) spectro-polarimetric studies. In this seminar, I will talk about the basics of the technique of spectro-polarimetry and a few science cases that could be benefitted from it. I will talk about the design and specifications of both instruments and share the latest assembly status of ProtoPol which currently is in the development stage. I will also discuss a simulation code that is being developed to simulate the performance of the M-FOSC-EP instrument.

Highlights of the sessions from the Asia Oceania Geosciences Society 20th Annual Meeting (AOGS2023)

Date: 2023-08-25
Speaker: Ms Neha Panwar
Venue: Seminar Room # 113/114 (Thaltej Campus

Abstract

The 20th Annual Meeting of the Asia Oceania Geosciences Society (AOGS) was held at Suntec, Singapore, between 30th July-4th August 2023. In this seminar, we shall be presenting an overview of the discussions carried out during the conference. We shall also be talking about the work that we presented at the conference.

Chemical Analysis of Nearby M Dwarfs Based on High-resolution Near-infrared Spectra Obtained by the Subaru/IRD Survey

Date: 2023-08-24
Speaker: Dr. Hiroyuki Tako ISHIKAWA
Venue: Online

Abstract

Chemical analyses of M dwarfs are scarce but necessary to explore the formation scenario and internal structure of planets orbiting them. I will talk about our spectral analyses of 71 mid- to late M dwarfs (2800 < Teff < 3400 K) observed in the Subaru/IRD planet search project (IRD-SSP survey). We used the high-resolution (∼70,000) near-infrared (970–1750 nm) spectra to measure the effective temperatures and the abundances of Na and Fe by the line-by-line analysis based on model atmospheres. For 13 objects of the targets, we also measured elemental abundances of Mg, Si, K, Ca, Ti, V, Cr, Mn, and Sr. The radial velocities we measured from the spectra were combine with Gaia astrometry to calculate the Galactocentric space velocities UVW. While the [X/Fe] distributions are comparable to those of nearby FGK stars, most of which belong to the thin-disk population and the most metal-poor object, Barnard's Star, could be a thick-disk star. The UVW velocities also support this. The results raise the prospect that near-infrared spectra of M dwarfs obtained in the planet search projects can be used to grasp the trend of elemental abundances and the Galactic stellar population of nearby M dwarfs.

Characterisation of Dust Detector Using Software Simulations

Date: 2023-08-18
Speaker: Mr Srirag Nambiar
Venue: Seminar Room # 113/114 (Thaltej Campus

Abstract

Asteroids in the belt between Mars and Jupiter, on collision, generate immense amounts of smaller dust particles. Comets leave out dust and gas when they move closer to Sun. In the size range of nanometers to millimetres, these particles undergo a dynamic evolution within the Solar system under the effect of different forces. By studying the present distribution, we can better understand the source, the particle’s evolution and the effect of different forces acting on the particles. Impact ionization dust detectors have been utilised for in-situ analysis of such particles, which have provided excellent results and improved our understanding of these tiny particles. We at PRL are also developing such a dust detector aimed at future planetary missions. Optimizing the configuration for the best performance of such an instrument becomes important. In this talk, I will be discussing different types of detectors used for studying these particles and simulations carried out using SIMION, a software package used to simulate the trajectory of charged particles under a static electric field. It is used to compare and optimize the voltage bias configuration of the detector. In interplanetary space, other than dust particles, the detector will encounter solar wind particles, GCR and radiation belt particles. GEANT4 toolkit is utilised to estimate the noise generated due to such particles and radiation. Results of computation carried out for an Earth orbit will be presented.

Spectral Ages of Remnant Radio Galaxies

Date: 2023-08-17
Speaker: Dr. Sushant Dutta
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The cessation of active galactic nucleus (AGN) jet activity can be well detected in radio galaxies with characteristic features such as absent core and jets, amorphous lobes of low-surface-brightness and strong spectral curvature. Radio galaxies with no AGN-jet activity are known as remnant radio galaxies (RRGs) which are believed to be rare objects. The scarcity of RRGs can be explained with the fact that they can be observed only over a relatively short time-window before they fade away due to radiative and dynamical energy losses. The time-scales of the active phase, remnant phase and AGN duty cycle are vital to understand the evolution of radio galaxies and related feedback. I shall present our ongoing work on estimating spectral ages of RRGs by modelling their radio spectral distributions (SEDs) with physically motivated models, namely, continuous injection (CION) and continuous injection-off (CIOFF) models. For our RRGs, we have obtained densely sampled SEDs across 144 MHz - 1.5 GHz using multi-frequency radio observations from LOFAR, uGMRT, MeerKAT and VLA. In this talk, I shall emphasize on the importance of newly acquired radio observations at band-3 (300-500 MHz) and band-4 (550-850 MHz) from uGMRT and L-band from MeerKAT, carried out under the superMIGHTEE and MIGHTEE projects respectively, which help us in placing better constraints on the spectral age estimates.

DWARF NOVAE: ACCRETION POWERED COSMIC FIREWORKS

Date: 2023-08-14
Speaker: Akash Sundriyal
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

A dwarf nova outburst is a very special and characteristic event undergone by a cataclysmic variable. These events are associated with the accretion disc as confirmed by recent observations. During a dwarf nova episode, the accretion disc brightens up by 2-5 magnitudes in typically a few days. This is a result of enhanced accretion onto the white dwarf as the disc becomes unstable. These events typically last for 2-20 days and occur semi-regularly. In this talk, I will briefly cover dwarf nova phenomenon and the mechanism responsible for it. The effect of mass-transfer rate and its role in shaping the outbursts will also be discussed. I shall also discuss the SED and TESS light curve analysis that has been carried out for the long-orbital period system V1948 Cyg.

Mechanical and Electronics design and development of Sun Tracking system for 2m dish antenna.

Date: 2023-08-04
Speaker: Vaibhav Jain, Ketan Agarwal, Hariom, and Yogesh Tailor
Venue: USO Seminar Hall

Abstract

Modeling the Ion Chemistry in The Coma of 67P/Churyumov-Gerasimenko

Date: 2023-08-04
Speaker: Ms. Sana Ahmed
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Comet 67P/Churyumov-Gerasimenko (67P/C-G) was the target of the ESA’s Rosetta mission that orbited in its vicinity for nearly 2 years. Rosetta carried a suite of instruments that provided in situ measurements of the neutral and ionic species in the gas phase coma. The species that were detected include the primary ions H2O+, CO+, NH3+, CH3OH+, CH4+ and C2H4+ that is mainly formed by the photoionization of parent molecules. The protonated forms of parent molecules that were detected include H3O+, HCO+, NH4+, HCNH+ and CH3OH2+. The continuous monitoring of the coma of 67P/C-G also led to measurements of neutral molecules during the entire mission period. While the relative abundances of neutral molecules can be converted to absolute values, it is difficult to know the absolute ion densities in 67P/C-G. We use a combined chemical-hydrodynamical multi-fluid model in order to understand the ionic composition and the coma chemistry in 67P/C-G. Our coma model is based on fluid conservation equations; it employs an extensive chemical network and uses the neutral gas production rates as inputs. Using the neutral gas production rates reported in the literature, we have modelled the coma of 67P/C-G at different heliocentric distances. We use our model outputs to make a quantitative analysis of the major ion creation and destruction processes at various orbital locations of 67P/C-G. We note that high proton affinity species such as NH4+ and CH3OH2+ have the highest abundances in the coma. The abundance of primary ions can be correlated to their parent molecule abundance in some parts of the coma. The H3O+/H2O+ ratio may be used to comment on the extent of ion-neutral chemistry. In this talk, I will give an overview of the coma observations by Rosetta, and discuss my model results on the ion composition and chemistry occurring in the coma of 67P/C-G.

Automatic Learning for the Rapid Classification of Events: ALeRCE

Date: 2023-08-03
Speaker: Amelia Bayo
Venue: Online

Abstract

Arguably, time domain (probably together with multi-messenger astronomy) is bound to change both, the way we "do observational astronomy" and what we know (and do not know) about the universe. Infrastructure like the Vera Rubin Observatory (VRO), for instance, will soon provide us with a much more dynamic view of a large portion of the night sky. The degree to which that kind of view can be scientifically exploited will heavily depend on our ability to generate more efficient data-flows and analysis tools, and the access to the right mid-size infrastructure for follow up. The Zwicky Transient Facility (ZTF) has been and is being used to test, improve, and prepare ourselves to deal with large data streams. All seven community brokers that will provide access for the general community to interesting variable objects detected by VRO are taking ZTF as the "training ground". In this talk I will present the work done by ALeRCE in particular (the only southern hemisphere broker) and how their services can provide a very interesting curated set of sources to be followed up by facilities related to your institute.

Ionic emissions in Comet C/2020 F3 (NEOWISE)

Date: 2023-07-31
Speaker: Dr. Aravind K
Venue: Room No. 113/114, Thaltej Campus, PRL

Abstract

The composition of molecular Nitrogen relative to CO and H2O has been sparsely studied in comets. The abundance of these neutral gases in the coma can be probed using optical spectroscopy only via their ionic emissions. While detecting and analysing them is crucial, it is equally challenging due to their very low density. Even though the Great Comet of 2020, C/2020 F3 (NEOWISE), has been studied in detail via very high-resolution spectroscopy, the presence of ionic emissions has not been reported in it. Long slit low-resolution spectroscopy of such bright comets can help analyse the spatial profile in great detail. This seminar will discuss the detection of the ionic emissions N2+, CO+, CH+ and H2O+, along with a few unidentified and unusual emissions in the spectacular comet C/2020 F3 (NEOWISE). While the computed relative abundances and their implications will be discussed, we also try to compare the unusual emissions observed in comet C/2020 F3 with the emissions which were also seen in the spectrum of comet C/1987 P1 (Bradfield) but remained unnoticed at the time.

Silicon Carbide/Diamond Electronics for extreme environments

Date: 2023-07-28
Speaker: Dr Narasimha Murty
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Silicon (Si) based electronics dominated the electronics industry for over seven decades. However, there are niche applications where the electronics is exposed to extreme conditions such as high temperatures, radiation environments, operation in liquid ambients where the conventional Is-electronics may not operate reliably. In this talk, the limitations of Si-electronics for extreme environments will be discussed. Potential wide-bandgap semiconductors such as Silicon Carbide (SiC), Diamond for operation under such harsh environments will be highlighted. Finally, the current technology, state-of-the-art and limitations of a SiC/Diamond will be covered.

Observations of Solar Corona Using Ground and Space-based Facilities

Date: 2023-07-27
Speaker: Dr. Sasikumar Raja
Venue: USO Seminar Hall

Abstract

Shock induced dust formation in novae

Date: 2023-07-27
Speaker: Dr. Ruchi Pandey
Venue: Room No. 113/114, Thaltej Campus, PRL

Abstract

Novae are the only objects in which it has been possible to observe directly all aspects of circumstellar dust formation on a frequent basis. Novae dust forms within a short time frame of typically 30 to 100 days after an outburst, allowing them to serve as test beds for understanding the formation and evolution of astrophysical dust. However, dust formation in the hostile environment of novae ejecta has been an open question for many decades. Several attempts have been made to understand the physical and chemical conditions required to dust formation in novae ejecta and its relation with the observable parameters. To explain the mechanisms underlying dust formation, numerous hypotheses have been proposed. In recent years, an intriguing hypothesis involving shock-induced formation of dust in novae has been proposed. A recent study of Nova V2891 Cyg by a PRL team provides, most likely, the first observational evidence of such a method of dust formation in novae ejecta. This seminar will commence with a concise introduction to the phenomenon of dust formation in novae, highlighting its significance and the current gaps in knowledge. Further, we will present the phenomenological cloudy modelling of Nova V2891 Cyg in order to illustrate the origin of some observational signatures of shock-induced dust formation.

Coronal Mass Ejections: From Observations to Simulations

Date: 2023-07-21
Speaker: Dr. Anshu Kumari
Venue: USO Seminar Hall

Abstract

The coronal magnetic field (B), the ultimate driver of space weather, plays an essential role in the formation, evolution, and dynamics of the small and large-scale structures in the solar corona. These structures lead to gigantic explosions in the solar atmosphere in the form of large-scale eruptions, such as coronal mass ejections (CMEs), which may severely impact near-Earth space. CMEs are often accompanied by radio emissions, which provide access to observations of the related solar, heliospheric, and ionospheric space weather phenomena. Radio techniques can provide early signatures of particle acceleration associated with solar flares and CMEs. Using radio observations and time-dependent data-driven numerical modeling of active region, I study the formation and eruption of the coronal flux ropes. I will highlight the radio techniques to constrain the initial CME properties close to the Sun and the numerical modeling approach to understand the initiation and evolution of large-scale solar eruptions. I will also talk about state-of-the-art ground and spaced-based radio instrumentation for solar and space weather studies.

The Study of organic matter in Meteorites

Date: 2023-07-21
Speaker: Ms Shreeya Natrajan
Venue: Seminar Room # 113/114 (Thaltej Campus

Abstract

The 23rd National Conference on Atomic and Molecular Physics was conducted at IIST in collaboration with Indian Institute for Science Education and Research (IISER), Thiruvananthapuram, Space Physics Laboratory (SPL), Thiruvananthapuram and Space Program Office (SPO), Bengaluru. Along with several posters and presentations, the conference had an exciting brainstorming session on “Origin of molecular life in space: new frontiers”. In this talk, I will present a brief overview of the discussions conducted during the conference and brainstorming session, along with a gist of my poster titled “Carbon nitrogen analysis of insoluble organic matter in meteorites”.

Unravelling the Origin Mystery of anomalously large lithium in red giants

Date: 2023-07-20
Speaker: Prof. Eswar Reddy
Venue: Room No. 113/114, Thaltej Campus

Abstract

In general, lithium gets destroyed in stars as they evolve. However, a small group of stars show excess lithium and, in some cases, more than the abundance seen in their natal clouds. The problem remained a puzzle for more than 40 years. With the availability of high-quality spectra for a large number of stars and asteroseismic data, we could now locate the source of high lithium abundance in red giants. In this talk, I will discuss and provide the current understanding of the origin of high Li in stars.

The Giant Molecular Cloud G148.24+00.41: Gas Properties, Kinematics, and Cluster Formation at the Nexus of Filamentary Flows

Date: 2023-07-20
Speaker: Mr. Vineet Rawat
Venue: Room No. 113/114, Thaltej Campus

Abstract

Giant molecular clouds (GMCs) are the cradles of young star clusters in which most stars form. Massive to intermediate-mass clusters play an important role in the evolution and chemical enrichment of the Galaxy through radiation and winds. However, the formation mechanism of stellar clusters, in particular, intermediate to massive clusters, is still not clear and a topic of debate. Determining and evaluating the physical conditions, kinematics, structures, and dynamics of massive molecular clouds (>10^5 Msun;) at their initial stages of evolution, such that stellar feedback effects are not significant there, are key to understanding the formation of stellar clusters. In this talk, I will present a case study of one such GMC, G148.24+00.41 having mass ~ 10^5 Msun; and size ~20 pc, based on CO molecular line data to understand its cluster formation scenario. I will present the role of filamentary flows in assembling the gas at the central gravitational potential of the cloud. I will discuss about the massive cluster formation scenarios given in the literature and their possibility in the G148.24+00.41 cloud.

Human Impact on Global Climate Change Over the Past Two Centuries: Use of Isotope-Tracing Techniques

Date: 2023-07-19
Speaker: Prof. Mark Baskaran

Abstract

The human impact on global climate change over the past two centuries is unprecedented. An incredible growth of population, from 1.5 billion in 1900 to 7.9 billion today has led to an increase in energy consumption by more than 1000% over ~70 years to power the development. Never in the history of the Earth has such a drastic increase in the atmospheric CO2, from 296 ppm in 1900 to 423 ppm in 2023, took place; it is attributed to energy extraction from non-renewable resources (e.g., fossil fuel) contributing ~85% of total energy consumption. The ‘science of the changing environment’ is at the forefront of human endeavor and a significant (and increasing) fraction of the global GDP is currently being spent on addressing this science (e.g., increasing spatial extent of harmful algal blooms, ocean acidification, ever increasing number of micro-plastics in fresh and saltwater systems, weather-related catastrophic events, etc). Isotopes of key chemical elements have been widely utilized to identify and quantify recent environmental changes. In this talk, a set of case studies, illustrating global environmental changes in different regions of global oceans will be presented.

Thermophysical property of Martian Gale crater region: Implications for active dust deposition phenomenon

Date: 2023-07-14
Speaker: Ms Farzana Shaheen, BIT, Mesra, Ranchi
Venue: Online

Abstract

In this presentation, I will discuss thermophysical properties in the Gale crater and its surroundings using satellite images from different Mars missions. Thermal Inertia (TI) is one of the significant thermophysical properties for planetary remote sensing applications. Estimating thermal inertia values is crucial in discriminating various surface lithologies and understanding the Martian surface's past and present geological processes. One of the investigated key parameter in this study include Thermal Inertia derived from Thermal Imaging Science Experiment (THEMIS) images. The result suggested seasonal variation in TI values, which depicts an active surface deposition process. Seasonal variation in TI values was influenced by dust; hence, Atmospheric Optical Depth (AOD) was retrieved using HRSC images; the result suggested that the predicted pressure scale height was equal to the scale heights derived for HRSC Nadir channel; also, one region consisted of clouds which added an extra AOD. Further, the influence of AOD on TI and particle size was investigated to understand the phenomenon responsible for dust deposition and lifting. In my proposed research work, I plan to investigate seasonal variations in atmospheric optical depth. These variations in the optical depth observed in images taken at different times can reflect the spatial distribution of optical depth. Understanding the spatial distribution and variation of atmospheric optical depth is necessary for the scientific exploration of the Martian lander or rover and its payload.

Implications from Galactic Archaeology to Exoplanets

Date: 2023-07-13
Speaker: Diogo Souto
Venue: Online

Abstract

M-dwarf stars, comprising approximately 70% of all stars in the Milky Way, are the most abundant type of star. However, they remain relatively understudied when it comes to their chemical abundances. This knowledge gap primarily arises from the complexity of their optical spectra, which are heavily influenced by strong molecular bands like TiO and VO. By leveraging near-infrared high-resolution spectra, we have been able to precisely determine stellar parameters and the abundances of up to fourteen elements in these stars. Given the increasing number of Earth-sized exoplanets discovered orbiting M dwarfs, there is a growing interest in characterizing these stellar objects. In this talk, we will explore how studying stellar abundances in M dwarfs can significantly enhance our understanding of Galactic archaeology to exoplanets.

Exploring Exoplanet Atmospheres: Impact of Atmospheric Metallicity on Composition and Observability

Date: 2023-07-07
Speaker: Mr. Vikas Soni
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

In the last 25 years, the number of confirmed exoplanets has risen significantly (more than 5000), from terrestrial earth-like planets to the massive gas giant Jupiter-like planet. In the current JWST era, the atmospheric characterization of these exoplanets has become the central theme in studying extrasolar planets. The atmospheric parameters and composition may provide information about planets' bulk elemental compositions, formation, and evolutionary histories. Molecules such as CO, CO2, CH4, H2O, NH3, and HCN, which are the building blocks for more complex organic molecules and significant reservoirs of elemental C, O, and N, have already been detected in exoplanet atmospheres. The abundances of these molecules are probed for the pressure level, where disequilibrium processes can dominate. Atmospheric metallicity is a crucial parameter that controls the total elemental abundance and, thereby, the atmospheric composition. In this seminar, I will discuss how the atmospheric composition of these exoplanets is affected by the atmospheric metallicity in the presence of the vertical mixing, along with a brief introduction of the methodology (1D photochemistry-transport model and quenching approximation) that I have used. I will also show the importance of this study in predicting the observability of chemical species and implementing the result in the atmospheric retrieval method, a common technique for retrieving atmospheric parameters.

Dust, Atmosphere, and Plasma Environment of the Moon and Small Bodies

Date: 2023-06-30
Speaker: Mr. Trinesh Sana
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The 4th Dust, Atmosphere, and Plasma Environment of the Moon and Small Bodies (DAP-2023) workshop is hosted by the SSERVI-IMPACT team at the University of Colorado, CO, USA. The workshop agenda included discussions on the current understanding of lunar and small-body surface environments, sharing results from past and ongoing missions, and addressing challenges and solutions for future dusty missions. I am going to present a brief overview of the lectures attended and activities undertaken at the workshop.

The role of outburst floods in Earth and Planetary Evolution

Date: 2023-06-16
Speaker: Dr S Vijayan
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Mariner 9 orbiter in 1972 discovered the first channel on Mars, which opened a new research area on how liquid water carved outflow channels. Further, different Mars orbiters provided comprehensive and numerous evidence for widespread, larger channels on Mars. Thus, a new era of comparative planetology emerged between Mars and Earth. On Earth, one of the major flooding events is the Missoula Floods and the Channeled Scabland, which act as a mega flood testing ground for studies that are comparable to Mars. The highly eroded Columbia river basalt bedrock preserved outburst floods produced features like huge cataract complexes, eroded canyons, large streamlined landforms, mega ripples, and immense stratified deposits. Study of the geomorphology and hydrology of outburst floods has, in turn, generated hypotheses regarding the role such floods play in driving climate change and a reater recognition of the geo-hazards associated with outburst flooding. However, the studies on Martian outflow channels revealed that the size, water quantity and the glacial landform are comparatively larger than that of the Earth. The Channeled Scabland formed by cataclysmic erosion and deposition from Pleistocene mega flooding still preserved the paleoflood indicators, which provide crucial clues to understand the magnitudes and frequency of flooding on Earth and Mars.

Introduction to Evershed and Inverse Evershed flows

Date: 2023-06-13
Speaker: Mr. Sandeep Dubey
Venue: USO Seminar Hall

Abstract

The Evershed flow is an outflow of plasma in the penumbra of a sunspot, first observed in 1909 by John Evershed at the Kodaikanal Solar Observatory, India. The Evershed effect is observed mainly in photospheric lines. The chromospheric lines such as H-alpha,CaII 8542 present an opposite picture in which an inflow of plasma is observed at chromospheric heights in the solar atmosphere. The inflow of plasma at chromospheric height, known as Inverse evershed flow, is present mainly outside the penumbral region of sunspots. In this talk, I shall introduce the flows with a brief discussion on observations dealing with different physical properties of the flows and models providing a possible mathematical structuring to the flows. I shall also discuss the aspects of these flows that we are working on at present.

Unraveling Mars' Magmatic Past: Insights from Martian Shergottites

Date: 2023-06-09
Speaker: Ms. Varsha M Nair
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The formation and evolution of the Martian surface, as well as the fate of its various volcanic regions, are revealed through the chemistry of Martian meteorites and the mineralogy of the crust. The composition, and consequently the evolution of the Martian crust and mantle have been elucidated through SNC (Shergottite-Nakhlite-Chassignite) meteorites. These meteorites serve as the igneous counterparts of rocks originating from Mars and have been brought to the surface through volcanism, offering a glimpse into the interior of the red planet. Martian meteorites, which carry different textures, mineralogy, trace element and isotopic patterns, provide an understanding of the igneous emplacement history of Martian magma and the heterogeneity of mantle reservoirs, thus revealing a complex history of Martian magmatic evolution. A texturally distinct variety of Shergottite is Poikilitic shergottite. This unique samples allow us to investigate how they formed from deep crustal chambers to late-stage evolution in the upper crust of Mars. In this talk, I will address the current understanding of the Martian mantle and its evolution through different meteorites, and specifically explore how poikilitic shergottites can provide further insights into the magmatic history of Mars.

Understanding crustal evolution of terrestrial planets through granitisation

Date: 2023-05-22
Speaker: Riya Debacharya Dutta, (MLSU, Udaipur)
Venue: Online

Abstract

To study the crustal evolution and composition of the terrestrial planets, a combination of global spectral imaging, optical imaging, gravity measurements, laser altimetry (remote sensing), in situ investigations, and laboratory analyses of returned samples are desired. Since there is a different level of planetary exploration for each of the terrestrial planets, our knowledge varies strongly among the planets with Mars and the Moon being the most studied bodies so far. For this study, understanding the geology of planet Earth should be very important as it reserves all the in situ evidences of terrestrial planetary evolution. It requires a much more comprehensive picture of the granitoid as it is a major sustainable component of earth’s continental crust. That can be achieved by studying them in regional way and it is necessary since granite result from both plate tectonic process and several magmatic processes (like liquid immiscibility, fractional crystallization, differentiation, partial melting as suggested from several experimental studies and petrological evidences in silicate systems from earth and other terrestrial bodies especially Lunar and Martian rocks) that can produce both new crust and recycle the older crust. In this research proposal, we consider a well-known Precambrian granitoid province as earth analogue to correlate the other granitic and felsic volcanism of inner terrestrial planets and thereby try to understand the role of granite for terrestrial crustal evolution.

Highlights of the sessions from the 54th Lunar and Planetary Science Conference (LPSC)

Date: 2023-05-12
Speaker: 1. Deepali Singh / 2. Yash Srivastava
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Probing the Solar Corona and Solar Wind Using Ground and Space-based Facilities

Date: 2023-05-09
Speaker: Dr. K. Sasikumar Raja
Venue: USO Seminar Hall

Abstract

Ground-based, low-cost low-frequency radio telescopes provide valuable insights into solar transient emissions such as solar flares and coronal mass ejections, and their association with solar radio bursts. Even after decades of intense research on solar radio bursts, we do not thoroughly understand their origin, emission mechanisms, polarisation properties, associated magnetic fields, white light counterparts, association with space weather, and many more. In this presentation, I will discuss the results derived using the observations from various facilities of the Gauribidanur radio observatory, space-based wind/waves, etc. Furthermore, I will discuss solar wind density turbulence and heating rates derived using the Crab Nebula occultation technique. I will also present the way the amplitude of solar wind turbulence, density modulation indices, and proton heating rates vary with the heliocentric distance and solar cycle. Apart from these scientific investigations, I will summarise my contributions to radio instrumentation and the Visible Emission Line Coronagraph (VELC) project. VELC is the internally occulted coronagraph onboard the Aditya-L1 mission, the first Indian mission to explore the Sun and solar corona.

On the chromospheric jets and the associated flows in the solar atmosphere

Date: 2023-05-04
Speaker: Mr. Ravi Chaurasiya
Venue: USO Seminar Hall

Abstract

Chromosphere forms one of the layers of the solar atmosphere sandwiched between the photosphere and the highly structured corona. It is highly complex and dynamic in nature, largely dominated by local magnetic field configuration, associated with spicules, jets, mottles, fibrils, etc. It is believed that they carry mass from the lower atmosphere to the higher atmosphere and are generated due to the leakage of p-mode oscillations or magnetic reconnection. In this seminar, I will talk about jet like structures, particularly spicules observed in the chromosphere, their generation mechanism, and the associated flows as they evolve through the solar atmosphere, using the observations from SST, MAST, IRIS, and SDO/AIA.

Shocked meteorites and its minerals: Impact-induced thermo-chemical evolution of asteroids and future planetary exploration

Date: 2023-04-28
Speaker: Kishan Tiwari, IIT, Kharagpur
Venue: Online

Abstract

The study of high pressure mineral polymorphs in shocked ordinary chondrites is key to comprehend its formation mechanisms, chemical compositions, and crystal structures in order to understand the dynamics of planetary interiors and the hypervelocity impact during the evolution of the early solar system. A comprehensive and interdisciplinary approach is always beneficial and utilizes the advanced analytical techniques to identify the shocked chondrite samples containing shock-melt veins and melt pockets. This further helps to decode the evidence of multiple impact events, further characterize the criteria to demarcate their specific characteristics in the form of textural imprints, and coalescing phases of contrasting magnitudes. This study will also investigate the origin of high-pressure phases, reconstruct the pressure-temperature-time path experienced, and evaluate the implications of high-pressure phases utilizing ultra-high-resolution electron microscopy. The results can also be used in future planetary missions to constrain fine-grained mineralogy adjacent to impact crater at close vicinity of the lander and rover on any planetary surface. The future research of high-pressure minerals also plays important roles to elucidate how the hypervelocity impacts of extraterrestrial materials affect Earth’s environments. In this talk, I will discuss the new results recently published in GRL, PNAS and JGR-Planets and the possible future scope.

Magnetic coupling of sunspot umbral atmosphere

Date: 2023-04-17
Speaker: Ms. Ananya Rawat
Venue: USO Seminar Hall

Abstract

Sunspots host various oscillations and wave phenomena like umbral flashes, umbral oscillation, running penumbral waves, and coronal waves. All the fan loops rooted in the sunspot umbra constantly show a 3-min period propagating slow magnetoacoustic waves in the corona. However, their origin in the lower atmosphere is still unclear. In this work, we studied these oscillations in detail along the clean fan loop system rooted in active region AR12553 for a 4-hour duration on June 16, 2016 observed by Interface Region Imaging Spectrograph (IRIS) and Solar Dynamics Observatory (SDO). We traced the footpoints of several fan loops at different atmospheric heights from the corona to the photosphere. We found presence of 3-min oscillations in the footpoints of all the loops at all the atmospheric heights. We traced the origin of these waves by utilising their amplitude modulation characteristics with time while propagating in the solar atmosphere. We found several amplitude modulation periods, such as 12 min, 22 min, and 35 min of these 3-min oscillations at all heights. Based on our findings, we interpret that 3-min slow magnetoacoustic waves propagating in the coronal fan loops are driven by 3-min oscillations observed at the photospheric footpoints of these fan loops in the umbral region. Results provide clear evidence of magnetic coupling of the solar atmosphere through the propagation of 3-min waves along the fan loops at different atmospheric heights.

Exploring Lunar Geochemistry Beyond Procellarum KREEP Terrain: Insights from Basaltic and Brecciated Meteorites

Date: 2023-03-31
Speaker: Yash Srivastava
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The geochemical evolution of the Moon is primarily understood in term of returned samples from the Apollo, Luna and Chang’E 5 missions. Although samples returned from the Moon provide valuable insight into its evolution, they are not a comprehensive representation because they are primarily collected from regions with high concentrations of incompatible elements, known as Procellarum KREEP terrain (PKT). The returned samples are dominantly mare basalts, anorthosite, and pyroclastic glasses which provide insight to interior processes such as volcanisms. Alternatively, breccias, which formed on the lunar surface offer us to understand exterior process such as meteoritic bombardment on the Moon. This talk will discuss the significance of the two different varieties of lunar meteorites in understanding the Moon's geochemical evolution. First, I will explain the petrogenesis of some KREEP-free lunar basalt meteorites which provides us insight to lunar mantle and its thermo-chemical evolution. Later, I will discuss about the lithological and compositional diversity of the lunar crust using the lunar breccia meteorites and the signatures of preserved external and internal processes in these samples.

Rapidity - dependent Jet vetoes at NNLL' + NNLO using SCET

Date: 2023-03-30
Speaker: Dr. Shireen Gangal
Venue: Room no: 469 (Main Campus)

Abstract

In this talk, I present resummed predictions for Higgs production via gluon fusion, and Drell-Yan production, in the framework of Soft Collinear effective theory (SCET). I introduce rapidity-dependent jet veto observables which provide a tight veto at central rapidities, gradually transitioning to a loose veto at forward rapidities. They divide the phase space into exclusive jet bins in a different way to the traditional jet veto observable pTjet. Using these rapidity-dependent jet vetoes, I present results for the 0-jet gluon-fusion Higgs cross section, and preliminary predictions for Drell-Yan at NLL’ + NLO and NNLL’ + NNLO. A significant reduction in perturbative uncertainty is observed going from NLL'+ NLO to NNLL'+ NNLO.

DEMYSTIFYING LEADERSHIP<img src='/prl-eng/images/red.gif'>

Date: 2023-03-29
Speaker: Prof. Asha Kaul
Venue: K R Ramanathan Auditorium, PRL Main Campus, Ahmedabad

Abstract

The concept of ‘leader’, ‘leader communication’ and ‘leadership’ has gained momentum over the years. Though there is a plethora of research on the topic of ‘leadership’ there is no one definition to which all practitioners and academics subscribe. There are differing outcome-based perceptions and then there are process focused assessments –the debate is ongoing and inconclusive. The question, - ‘Where then can we draw our leadership lessons from?’, becomes all the more pertinent in this environment of uncertainty. I propose that knowledge on the topic can be derived from one of the oldest and longest epics of India – Mahabharata. Written in the third century BC in the form of Itihaas (history), it presents narratives of leader stratagems and propels the reader to draw lessons for almost all fields of operation. All characters in Mahabharata have a narrative which advocates strategies for people in leadership positions or which may be termed as the Leadership Act on how mindsets are created, plans are communicated and executed, the role of love, passion, hatred and envy and the consequences of the same. The legitimacy of the leadership act – embedded in the moral as well as pragmatic – leads us to the notion of Principled Pragmatism, that is, ethical principles, character and relationships. And what better text than Mahabharata is there which can teach us through the narratives principles of leadership – what should be followed and what should be avoided.

Study of Reconnection Dynamics and Plasma Relaxation in MHD simulation of a Solar Flare

Date: 2023-03-27
Speaker: Mr. Satyam Agarwal
Venue: USO Seminar Hall

Abstract

During solar transients such as solar flares and jets, the stored magnetic energy is released explosively in the form of heat and acceleration of the charged particles. The underlying cause of these transients, i.e. the magnetic reconnection process has long been associated with the self-organization or relaxation of magnetized plasmas. In this regard, Taylor's theory (1974) has been investigated quite extensively during the past few decades but a thorough understanding of the relaxation process is still a long way off. While previous studies have focused mostly on analytical magnetic fields, we adopt a novel approach in this study and utilize the data-constrained magnetohydrodynamics (MHD) simulation of an observed solar flare as the governing framework to explore relaxation and to test the predictions of Taylor's theory. The selected active region NOAA 12253 hosts a GOES M1.3 class flare. The investigation of extrapolated coronal magnetic field in conjunction with spatiotemporal evolution of the flare reveals a hyperbolic flux tube (HFT), overlying the observed brightenings. Further, MHD simulation is carried out with the EULAG-MHD numerical model to explore reconnection dynamics. Three distinct sub-volumes are chosen and are subjected to analysis of magnetic field line dynamics along with time evolution of various physically relevant quantities such as magnetic energy, current density, twist, and gradient in magnetic field. In my talk, I will be presenting the theory of self-organization, helicity, MHD relaxation, and Taylor’s relaxation followed by results, summary, and discussion.

Spontaneous generation and annihilation of three-dimensional magnetic nulls

Date: 2023-03-23
Speaker: Mr. Yogesh Maurya
Venue: USO Seminar Hall

Abstract

Three dimensional (3D) magnetic nulls are the location where magnetic field is zero. They are preferential sites for magnetic reconnection and triggering solar coronal transients, for example: solar flares, coronal mass ejections and coronal jets. Such 3D nulls are abundant in solar atmosphere but mechanism of their generation or the reason of their abundance is yet a puzzle. Toward solving this puzzle, the dynamics of an analytical initial magnetic field having an isolated current-free 3D null is numerically simulated with initially prescribed flow. The flow facilitates reconnections, which lead to the generation of primary null pairs in a way that preserves the topological degree. The formation process of these null pairs is novel and different from the standard pitchfork bifurcation. In standard pitchfork bifurcation the additional nulls get created within the current layer developed at the central null. Contrarily, here we found creation of null pairs away from the central null, which we hypothesize is due to the interaction of the imposed flow and the reconnection outflow from the central current layer. Intriguingly, further evolution spontaneously generates new null pairs, which have a novelty by itself. As theorized, these spontaneously generated null pairs also preserve the net topological degree—adding credibility to the simulation. The simulation also shows null pair annihilation. In the talk, I will discuss the results in detail together with the identified mechanism responsible for the generation and annihilation of the nulls.

Some experiments of relevance for PAHs in the Solar System

Date: 2023-03-17
Speaker: Dr. Vinitha M V, Postdoctoral researcher, PIIM Laboratory, Aix-Marseille University, Marseille, France
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are one of the dominant organic compounds present in the extraterrestrial rocks formed in the early solar system. These molecular species have already been detected in many other astronomical environments. Much laboratory astrophysics research in the past few decades has been dedicated to investigating the molecular properties of PAHs. It is widely accepted that these molecules become highly reactive after interacting with various astronomical radiations and form nitrogen and oxygen containing aromatic organic molecules [1]. Some of them are already detected in carbonaceous chondrite (CC) meteorites. Apart from this perspective, meteoritic PAHs are nowadays seen as a possible tracer of various physical conditions under which these primitive rocks are formed or evolved. GC-MS is an established technique for high-level molecular analysis on meteoritic PAHs. But this technique requires sample to be available in milligram quantities and never enables the determination of spatial distribution of PAHs across a given sample. In this context, several other mass spectrometric techniques are emerging in the field. One of them is microprobe two stage laser desorption laser ionization mass spectrometry. One such instrument called AROMA is available in IRAP, Toulouse, France. This instrument is specially designed to perform high level molecular analysis on meteoritic PAHs. For instance, very recently this instrument is coupled with a third laser to enable direct detection of m/z 202.02 PAH isomers (one of the most abundant PAH in different carbonaceous samples) by visible multiphoton dissociation. The technique in detail and the results on multiple CCs will be discussed in the talk. Moreover, another unique mass spectrometric technique developed at AMP, IIST, Thiruvananthapuram to investigate various astronomically relevant dissociation channels of PAHs will also be discussed in the seminar.

Design, Development and Performance Modelling of WALOP Polarimeters for PASIPHAE Survey

Date: 2023-03-16
Speaker: Dr. Siddharth Maharana
Venue: Thaltej Seminar room (113)

Abstract

PASIPHAE survey aims to create the first large sky magnetic field and dust cloud tomographic map of the Galactic polar regions using stellar polarimetry and GAIA stellar distances. Two WALOP (Wide-Area Linear Optical Polarimeter) instruments, to be mounted on 1 m class telescopes in South Africa and Greece are currently under development to work as survey instruments for the PASIPHAE program for creating the stellar polarization catalogue. Scheduled for commissioning in 2023, the WALOPs are being designed to operate with the combined capabilities of one-shot four camera linear polarimetry, low polarization systematic (polarimetric accuracy of 0.1%) and a large field of view of 30×30 arcminutes, which in combination will make these unique astronomical instruments. Operating in the SDSS-r broadband and narrowband filters between 500-700 nm, for each exposure, four images of the full field corresponding to polarization angles of 0, 45, 90 and 135 deg will be generated and carrying out differential photometry on these images will yield the linear Stokes parameters. We have developed a complete design and calibration strategy for WALOPs to achieve its technical goals. In this talk, I will present an overview of the instrument design, development, performance modelling and calibration routine for the instruments and their current status.

Reviving the sterile neutrino dark matter with neutrino secret self-interactions

Date: 2023-03-16
Speaker: Dr. Manibrata Sen
Venue: Online ---> https://bluejeans.com/512808345/1781

Abstract

Sterile neutrinos with masses around a few keV have been postulated to be viable dark matter candidates. This is, however, mostly in tension with various astrophysical observations, the most stringent being the X-ray bounds. In this talk, I would like to present a testable sterile neutrino dark matter production mechanism in the early Universe. The idea is to introduce a light scalar particle that mediates self-interactions among the Standard Model neutrinos. Such interactions enable the sterile neutrinos to be more efficiently produced in the early universe, thus alleviating the tensions and allowing the sterile neutrinos to be perfectly lucrative dark matter candidates. Such secret self-interactions can be tested in future neutrino experiments like DUNE. Apart from laboratory bounds, I will also discuss how these interactions can lead to exciting signatures in the early Universe as well as core-collapse supernovae.

Martian meteorite and hydrogeology on Mars

Date: 2023-03-10
Speaker: Aditya Das
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

In contrast to the Noachian era, the Amazonian era is drier, so the extent of the water-rock interaction on Mars during the Amazonian is limited to the secondary minerals (clays) found in the Nakhlite group of Martian meteorites. The Nakhlite group of meteorites are clinopyroxene-rich igneous cumulate rocks that are thought to be formed from thick lava flow or shallow sill. In this study, the alteration products in the Nakhlites will be analyzed to understand the reaction between the primary crust with liquid water in the recent Amazonian era. Thus, this study will help us to understand many important aspects, like the possible pathway for fluid circulation, the relative lifetime of formation of secondary minerals, and the nature of the reacting fluid/s bringing about such alteration.

Bosonization, Chiral L¨uttinger Liquid, Spin chain and Quantum Hall

Date: 2023-03-02
Speaker: Dr. Ankur Das
Venue: Room no: 469 (Main Campus)

Abstract

Bosonization is a general technique/formalism that helps us in taking 1D interacting fermion problem and turning them into effective non-interacting boson problem. I will talk in detail about the formalism, the assumptions, and the basics. I will go through also the mapping between operators and Hamiltonian in these two languages. I will discuss how they connect to the quantum Hall edge mode (Chiral L¨uttinger Liquid). Next, I will discuss the same for a simple spin chain model (XXZ spin chain) and how that can be mapped to L¨uttingerLiquid and neutral modes (spin wave). I will then discuss how interaction can play a role in detecting these neutral modes that we have discussed in our work [PRB 105, 165154 (2022)]

The Solar System's Great Divide

Date: 2023-03-01
Speaker: Dr. Ramon Brasser, Senior planetary scientist, Research Centre for Astronomy and Earth Sciences, Budapest, Hungary
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The Solar System is divided into two distinct regions: the inner and the outer part. The inner solar system is populated by small, rocky planets while the outer solar system's inhabitants primarily consist of the four giant planets.How did this architecture come about? How did the rocky and giant planets form, on what timescale, and from what materials? My research focuses on using numerical N-body simulations and isotopic anomalies and chronology from extraterrestrial samples to piece together the dynamical history of the solar system. In this presentation I give an overview of my work, what we know, what we don't know, and briefly mention a pathway for future research.

Topological Semimetals beyond regular

Date: 2023-03-01
Speaker: Dr. Ankur Das
Venue: Room no: 469 (Main Campus)

Abstract

Topological semimetals in three dimensions occur in mainly two variants, with the bands touching at point nodes (Weyl or Dirac semimetals) or touching at nodal lines in the Brillouin zone. However, there are new semimetals that challenge our notion, namely Nexus. Their existence needs lattice symmetry their classification needs an extra understanding of the system than usual. I will discuss how to understand the topology of Nexus Semimetals. On the other side while Weyl/Dirac semimetals can occur with internal symmetries only (such as time-reversal, charge conjugation, and possibly a product of the two, called chiral/sublattice symmetry), nodal line semimetals have been believed to require more symmetry, such as SU(2) spin rotation or crystalline symmetries. Though there has been discussion about possible topological classification of nodal line, how does in a generic the symmetry-constrained model they appear is not understood well. We show that chiral symmetry classes that are topologically nontrivial in three dimensions (namely class AIII, CII, DIII, and CI) always have a stable gapless phase, which is a topological nodal line semimetal even for the minimal model. We emphasize that no lattice or spin rotation symmetries are required for their robustness.

Su-Schrieffer-Hegger model with a non-orientable bulk: Union of topology and flat bands in one dimension

Date: 2023-02-28
Speaker: Bharathiganesh D
Venue: Room no: 469 (Main Campus)

Abstract

The Su-Schrieffer-Hegger model is the most simple but complete model of topological band insulators exhibiting features like bulk boundary correspondence. We investigate the possibility of the bulk in this model being a non-orientable manifold and consequences thereof. We find that in this case the topology of the SSH model is preserved along with the appearance of a doubly degenerate flat band at the Fermi level. We also find that there are states localised in the bulk along with the non-trivial edge modes in a finite chain. We will begin the talk with an introduction to band topology through the SSH model and continue to the case with non-orientable bulk.

Modelling of Cometary Atmosphere

Date: 2023-02-24
Speaker: Kinsuk Acharyya
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Comets are made up of the leftover materials that formed our solar system and are the least altered objects surviving the protoplanetary disks. They are the building block for the cores of outer planets and transport water and organics throughout the planetary system. Also, it played a crucial role in the habitability of terrestrial planets. Thus the study of comets and their composition is of paramount importance. Most information about comets comes from studying their atmosphere or coma, formed during perihelion passage. Active chemistry occurs in the coma, and the energy released due to chemical reactions is non-uniformly distributed amongst the volatile species in the coma, resulting in different temperatures. Numerical simulation can be employed to understand the formation of cometary volatiles in the cometary coma. We developed a multifluid numerical model to study how the chemistry and dynamics of the coma of a comet change for varying abundances of the major volatiles, which will be discussed in the presentation. The model uses the fluid conservation equations for number density, mass, momentum and energy. It considers neutrals, ions and electrons as three separate fluids. Besides chemical reactions, we have also considered the energy exchange between the three fluids due to elastic and inelastic collisions. The fluid conservation equations can be written as first-order differential equations in species number density, velocity and temperature. Numerical integration of these equations gives the temperature and velocity profiles of the coma for varying cometocentric distances. In the presentation, I will discuss various facets of the modelling of the cometary atmosphere and our study of the coma of the first interstellar comet 2I/Borisov and a few other comets, emphasising the formation of organic species.

Near infrared background with the 1.2 m telescope at Mount Abu

Date: 2023-02-23
Speaker: Ms. Prachi V. Prajapati (Scientist/Engineer SD, A&A division PRL)
Venue: Room no. 113/114 Thaltej

Abstract

Study of the background in astronomical observations plays a crucial role in understanding the characteristics of background noise. In this seminar, I will be discussing the estimation and analysis of the Near Infrared (NIR) background for the astronomical site at Mount Abu. Data obtained from the NIR observations of various sources using the Near Infrared Camera/Spectrograph (NICS) on the 1.2 m telescope are used in this study to derive the NIR background estimates. We notice seasonal variations in these values, with the summer months showing slightly brighter background compared to the winter. A comparison of synthetic atmospheric transmission at Mount Abu with other Indian observatories at various altitudes will also be presented. We identify the plausible contributors to the NIR background in our observations and discuss the potential ones that can contribute to the noticed seasonal variations. Overall, we find that the NIR background does not show any systematic variation over the period of the observations from 2010 to 2019.

Out-of-time-order correlators of nonlocal block-spin and random observables in integrable and nonintegrable spin chains

Date: 2023-02-23
Speaker: Mr. Rohit Kumar Shukla
Venue: Online ---> https://bluejeans.com/299910903/4490

Abstract

Out-of-time-order correlators (OTOC) in the Ising Floquet system, that can be both integrable and nonintegrable is studied. Instead of localized spin observables, we study contiguous symmetric blocks of spins or random operators localized on these blocks as observables. We find only power- law growth of OTOC in both integrable and nonintegrable regimes. In the non-integrable regime,beyond the scrambling time, there is an exponential saturation of the OTOC to values consistent with random matrix theory. This motivates the use of “pre-scrambled” random block operators as observables. A pure exponential saturation of OTOC in both integrable and nonintegrable systems is observed, without a scrambling phase. Averaging over random observables from the Gaussian unitary ensemble, the OTOC is found to be exactly same as the operator entanglement entropy, whose exponential saturation has been observed in previous studies of such spin-chains.

Lunar Surface Thermophysical Behaviour - Complications and Implications

Date: 2023-02-17
Speaker: Durga Prasad Karanam
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Jupiter’s saltwater ocean world Europa: a template for life beyond Earth and alkali-rich exomoons beyond the solar system

Date: 2023-02-10
Speaker: Dr. Apurva V. Oza (Chief Scientist Postdoc, JPL (USA))
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Jupiter’s innermost Galilean satellite Io is the most volcanic body in the solar system, orbiting at ~6 Jovian radii. The subsequent Europa at ~9.6 Jovian radii also experiences tremendous tidal heating — melting its ice and possibly cryovolcanically venting saltwater into its exosphere. Europa’s sodium & potassium (Na/K) exosphere is sputtered from its brine-rich surface forming a patchy sodium torus directly linked to its outgassing and possibly its oceanic interior, conducive to life. With the aid of evaporative transmission spectroscopy, neutral sodium and potassium are regularly observed at transiting gas giant exoplanets. Here we show how dozens of exomoon candidates, >> 10,000x more powerful in mass flux than Io and Europa, may be actively populating the exospheres of exoplanets. Especially compelling exomoon candidates showcase spectral disappearances of Na&K at select systems, meriting follow-up by high-resolution and space-based spectrographs onboard HST/JWST.

Accretion around black holes: The geometry and spectra

Date: 2023-02-09
Speaker: Narendranath Layek
Venue: Room no. 113/114 Thaltej

Abstract

The most energetic phenomena of our universe are generally powered by the process of accretion onto compact objects. This process releases energy through radiation. When accreting material has angular momentum, it forms a disc-like structure around the central object at the equatorial plane is called an accretion disc. There are various types of disc mechanisms present in the literature. Between them, the Standard disc, proposed by Shakura and Sunyaev in 1973, is the most preferred disc model, which is used widely to explain the disc accretion around any compact object. This model predicts disc properties like spectral energy distribution and luminosity and has been validated by observations of various astrophysical systems. In this talk, I'll give a brief overview of various accretion processes, including disc accretion and the associated radiation mechanisms.

Remote sensing studies of planetary regolith surfaces: Topographic mapping, reflectance spectroscopy, photometry, polarimetry, thermal modelling, machine learning - and linking them all up

Date: 2023-02-08
Speaker: Prof. Christian Wöhler (Image Analysis Group, Technical University of Dortmund, Dortmund, Germany)
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

This talk provides an overview of a variety of remote sensing methods developed at the Image Analysis Group of TU Dortmund University, operating in the visible, near-infrared and thermal infrared wavelength domains. Applications to the Moon, Mars, Mercury and an atmosphereless exoplanet demonstrate the wealth of information obtainable by such techniques once they are mutually linked up. Particular emphasis is dedicated to (i) the topographic and thermal correction of reflectance spectra from planetary regolith surfaces, (ii) the resulting time-of-day-dependent detection of surficial water/hydroxyl on the Moon, (iii) the estimation of elemental and mineral abundances based on hyperspectral imaging, (iv) the determination of physical regolith properties such as small-scale roughness, porosity and grain size, and (v) automatic geomorphological mapping.

TPC #7: Measuring Entanglement in Electronic Interferometers

Date: 2023-02-07
Speaker: Prof. Yuval Gefen
Venue: K. R. Ramanathan Auditorium, PRL main campus

Abstract

This talk will rely on two fundamental themes of quantum physics: the statistics of identical particles, and entanglement. The former was thrust into the limelight, given the theoretical and experimental search for anyonic (fractional) statistics. The latter is a pillar of quantum mechanics: quantum entanglement prevents us from obtaining a full independent knowledge of a subsystem. Can one, theoretically and experimentally, focus on and isolate statistics-induced entanglement? Here I will address this question, addressing the case of fermions.

Dynamical Generation of Dark Matter and Electroweak Scales

Date: 2023-02-01
Speaker: Dr. Anish Ghoshal
Venue: Online ---> https://bluejeans.com/482088260/6256

Abstract

The Standard Model (SM) of particle physics suffers from the hierarchy problem which can be ameliorated if all the scales that we observe in nature are considered not to be fundamental but generated dynamically in nature. As examples, we will discuss freeze-out and freeze-in production of vector dark matter (DM) in a classically scale invariant theory, where the Standard Model (SM) is augmented with an extended gauge symmetries that are spontaneously broken due to the non-zero vacuum expectation value (VEV) of a scalar. Generating the SM Higgs mass at 1-loop level, it leaves only two parameters in the dark sector, namely, the DM mass mX and the gauge coupling gX as independent. For freeze-in, which require very feeble coupling to satisfy the relic, the scenario is testable in several light dark sector searches (e.g., in DUNE and in FASER-II) as well as direct detection probes in a complementary manner courtesy to the underlying scale invariance of the theory. We will show scenarios for neutrino-portal, axion-portal, Zprime-portal and HIggs-portal freeze in DM. In the second part of the talk we will briefly show how gravitational waves can be used to test freeze-in DM and complemented with laboratory signals.

From hot Jupiters to super-Earths: Exoplanets and beyond

Date: 2023-01-31
Speaker: Dr. Priyanka Chaturvedi
Venue: Thaltej Seminar room (113)

Abstract

The search for planets beyond our solar system is one of the biggest scientific quests at present. The first exoplanet detection by the radial velocity (RV) method nearly three decades back was awarded the Nobel prize in Physics. Since then, the number of exoplanets found has increased exponentially with nearly 5000 exoplanet detections till date. We have learnt that diverse planetary systems form with orbits, densities, and planetary atmospheres that are very different from the planets in our solar system. In my talk, I will discuss planet demographics across the stellar spectral range focusing on large planets around the solar-type stars and smaller planets around the late spectral type stars. Despite the advent of large telescopes and precise spectrographs, the detection of smaller planets is largely limited by the intrinsic stellar jitter. I will talk about the ways that we devise to disentangle this stellar jitter from the planet signature. I will finally highlight the role of small to medium-size telescopes for exoplanet characterization in the era of current and future space missions like TESS and PLATO.

On the origin of a kiloparsec size superbubble in the JWST images of the "phantom galaxy" NGC628

Date: 2023-01-23
Speaker: Prof. Yalia Divakara Mayya
Venue: Thaltej Seminar room (113)

Abstract

NGC628 is the first nearby galaxy for which JWST data became available to the public. The most striking characteristic of the publicly released MIRI image is the presence of a large number of "holes" in an otherwise bright mid-infrared (MIR) emitting disk. This porous structure has given it a popular nickname "phantom galaxy". The "holes" are most often expanding bubbles or superbubbles that are created by the mechanical power output by the massive stars in young star clusters. However, few cases exist where the stellar population that was responsible for the creation of the bubble was unambiguously identified. We here analyze the largest of the bubbles in the JWST/MIRI image of NGC628, measuring 1.3 kpc in diameter to understand the origin of such large bubbles. We combined the JWST NIRCam and MIRI dataset with archival images from the HST, ALMA, VLA and MUSE, to identify the resolved population that might be responsible for the creation of the bubble, and to map the multiphase morphology and kinematics of the gas in the shell surrounding the bubble. The bubble is dominated by the molecular gas and is expanding at 12 km/s velocity. We find conclusive evidence for the presence of a resolved stellar population of ages between 5 to 50 Myr inside the bubble, whose collective mechanical power output is sufficient to explain the presently observed radius, velocity and the shell mass. In the talk, I will discuss the star formation scenario inside the bubble and the conditions that favour the formation of large superbubbles.

An extremely enhanced ionization in the E region ionosphere of Mars: Modelling and observations

Date: 2023-01-23
Speaker: Siddhi Shah
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) experiment onboard Mars Express (MEX) observed a few events of extremely strong ionizations when the E-peak electron density enhanced significantly at altitude ~90-100 km. These observations were carried out in the mini-magnetosphere of Mars between latitude 54oS to 55oS and longitude 177oE to 182oE. Observation of such strong density at this low altitude demands a source mechanism. We report an unusual event on 2 June 2012 of MARSIS onboard MEX during orbit # 10723 at Ls 119o, when the E-peak electron density ~1.7 x 105 cm-3 enhanced significantly at altitude ~ 100 km. This peak density is higher by about an order of magnitude from the E peak density observed by Radio Occultation Science Experiment (ROSE) onboard Mars Atmospheric and Volatile Evolution (MAVEN). We have modeled observed electron density profiles using coupled continuity and Analytical Yield Spectrum (AYS) approach. The estimated electron density due to solar EUV/X-ray is matching well with the ROSE observation. The enhanced E-peak density in the MARSIS profile is produced due to high-energy electron impact.

The Phase puzzle of ν = 0 (charge neutrality) Graphene and Beyond

Date: 2023-01-19
Speaker: Dr. Ankur Das
Venue: Online ---> https://bluejeans.com/955982537/8037

Abstract

The true ground state of ν = 0 (charge neutrality) monolayer graphene quantum Hall has long been debated. Famously the symmetry of the monolayer graphene at ν = 0 (charge neutrality) was analyzed by J. Alicea and P. A. Fisher (PRB 2006), and canted anti-ferromagnet (CAF) was predicted by I. F. Herbut (PRB 2007). However, the complete picture of the Hamiltonian was missing until the seminal paper by M. Kharitonov (PRB 2012), which predicts a phase transition from a vanilla insulator (CAF) to a topological insulator Ferromagnetic phase (F) as one changes the Zeeman energy keeping the cyclotron energy fixed. This was later confirmed in the experiment by A. F. Young et al. (Nature 2014). Motivated by recent experiments (L. He et al. PRB 2019; Ali Yazdani et al. Science 2022; B. Sacepe et al. Nature 2022), we revisit this phase diagram. We show that, generically, in the regime of interest, there is a region of coexistence between magnetic and bond orders in the phase diagram. We demonstrate this result both in continuum and lattice models and argue that the coexistence phase naturally provides an explanation for unreconciled experimental observations on the quantum Hall effect in graphene. We further extend this idea to the whole phase diagram. This opens up many questions about different possibilities and new ideas, and possible mesoscopic experimental consequences.

Non-monotonic potential structures within lunar photoelectron sheath

Date: 2023-01-13
Speaker: Trinesh Sana
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

A dusty photoelectron sheath near the sunlit lunar surface is anticipated under the dynamic interaction between solar irradiation and ambient plasma. Determining the justifiable electric potential structure within the lunar photoelectron sheath has been an active area of interest. Electron distributions measurement of Lunar Prospector (LP) above the dayside lunar surface indirectly implied the existence of a non-monotonic electric potential structure near the lunar surface. I will be discussing the physics behind the non-monotonic potential structure formation using justified solar spectrum, solar wind flux, and adequate photoelectron distribution.

Hard X-ray polarimetry with CZT Imager onboard AstroSat: An overview of the technique and recent scientific findings

Date: 2023-01-12
Speaker: Dr. Tanmoy Chattopadhyay
Venue: Thaltej Seminar room (113)

Abstract

CZT Imager onboard AstroSat is primarily a hard X-ray spectroscopic instrument but provides sensitive polarization measurements above 100 keV for bright X-ray sources, e.g. Crab pulsar and the Cygnus X-1 black hole system. With an accumulated 800 ks of observation, CZTI provided till date statistically the most significant polarization measurement for Crab. Phase-resolved polarimetry of the pulsed radiation of Crab was also attempted for the first time in X-rays and the findings provided interesting insights to the emission site of hard X-rays. In the case of Cygnus X-1, the recently dedicated long AstroSat observations show a strong dependence of polarization properties on the spectral state of the source. This is an interesting finding and might be useful in understanding possible disk-jet interplay in black hole systems. Another important characteristic of CZTI is the increasing transparency of the support structure in hard X-rays, which enables it to function as a wide field hard X-ray monitor providing an unique opportunity for GRB detection and polarization measurement. From a sample of a large number of GRBs detected by CZTI in the last 5 years, we attempted polarization measurement for 20 bright GRBs. Time integrated analysis of the prompt emission yields low or no polarization indicating that GRB prompt emission is highly structured leading to possible changes in the polarization angle within a burst which has also been seen independently for some of the bright AstroSat GRBs. A large sample of such polarization measurements in the future is supposed to shed more light into the emission mechanism of GRB prompt emission. In this presentation, I would briefly discuss these recent scientific findings from CZTI. Polarization measurement in hard X-rays for CZT based large area instruments is challenging because of multiple factors, e.g. large background, difficulty in reconstructing the Compton events properly in a single crystal detector plane, systematic effects because of square pixel geometry and the effect of charge sharing. Polarization measurements also critically depend on the accuracy of the mass model of the instrument and the spacecraft particularly for off-axis sources like GRBs. We inspected each of these effects carefully and developed our analysis algorithm over the last few years. I would highlight these challenges and their effects in the context of CZTI polarimetry technique.

Development and characterization of fast low noise X-ray detectors for the next generation astronomical observatories.

Date: 2023-01-10
Speaker: Dr. Tanmoy Chattopadhyay
Venue: Thaltej Lecture room (113)

Abstract

The next generation of large X-ray astronomical missions (e.g. the Lynx Great Observatory and AXIS probe class mission concepts) are planned to have an order-of-magnitude larger collecting areas combined with exquisite mirror quality, enabling unprecedented exploration of the faint and high redshift X-ray universe. An essential component of these mission concepts is the development of focal plane instrumentation with fast readout and excellent noise performance - crucial especially for the soft X-ray performance - on the order of single electrons. MIT Lincoln Laboratory (MIT-LL), MIT Kavli Institute (MKI) and Stanford University (SU) have together made substantial improvements in developing next generation X-ray CCDs, and associated readout electronics to support these detectors. We recently characterized a prototype CCD at 4 Megapixel/s (40 times faster than Chandra CCDs) with good noise performance. In parallel, we are also working on a novel Single electron Sensitive readout stage (SiSeRO) for CCDs, and potentially active pixel sensors, which can in principle provide even greater responsivity and better noise performance than contemporary JFET technology. The SiSeRO technology uses a p-MOSFET transistor with a depleted back gate region beneath the transistor channel. The transistor source-drain current is modulated by the transfer of charge into the back gate region. The first SiSeRO prototype devices already achieve a charge to current conversion gain of >700 pA per electron, an equivalent noise charge (ENC) of 4.5 electrons root mean square (RMS), and a full width half maximum (FWHM) of 130 eV at 5.9 keV at a readout speed of 625 Kpixel/s. Importantly, utilizing the benefit that the charge signal remains unaffected by the readout process in these devices, we have also been able to implement Repetitive Non-Destructive Readout (RNDR) on our prototype devices, achieving significantly improved ENC performance. In this talk, I will discuss the working and characterization test results for these new fast, low noise X-ray CCDs and the novel SiSeRO devices.

Geochemical study of Martian meteorites

Date: 2023-01-06
Speaker: Varsha M Nair
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Significant insight into Mars has been gleaned from the ~260 Martian meteorites. In the absence of a sample return mission, meteorites are the only samples available from Mars. However, with addition of new meteorites and ever-growing dataset of surface compositions, new perceptive about the chemical condition and evolution of Mars has been recently understood. The shergottites are the most abundant type of Martian meteorites, accounting for 89% of the total collection by number and 82% by mass. Shergottites are geochemically classified based on their relative enrichment or depletion in incompatible trace elements (ITE), and these ITE compositions are largely inherited from their mantle sources. Shergottites can also be classified into different groups according to their texture, and different textures represent mineral formation and emplacement in the shallow subsurface or perhaps eruption at the surface, which gives an understanding of the igneous emplacement history of Martian magma. As a result, the study of Shergottite samples provides various insights into the Martian interior and the extent of its heterogeneity. In this presentation, I’ll be briefly discussing about different type of Shergottites and how the study on the samples can give insight on the interior of Mars.

A Type I+II seesaw model without Electroweak (EW) hierarchy

Date: 2023-01-06
Speaker: Debashis Pachhar
Venue: Room no: 469 (Main Campus)

Abstract

The Standard Model (SM) has passed all the precision tests in the past decades and provides the best description of the Electroweak (EW) and Strong interaction in nature. However there are motivations to tread beyond the SM, one of which is neutrino oscillations which established that neutrinos have small but non-zero mass. The most elegant mechanism to generate such small masses is the seesaw mechanism in which the smallness of neutrino masses is explained by introducing one or more heavy particles at a high scale. Two popular variants of these are the type-I and type-II models which require induction of singlet neutrinos and triplet Higgs fields respectively. Both these models are phenomenologically attractive but they suffer from the EW hierarchy problem. In this talk, I will explore the possibility of addressing this issue in the context of the type I+II seesaw model.

Deciphering the \sim 18 TeV photons from GRB 221009A

Date: 2023-01-05
Speaker: Prof. Sarira Sahu
Venue: Room no: 469 (Main Campus)

Abstract

On 9 October, 2022, an extremely powerful gamma-ray burst, GRB 221009A, was detected by several instruments. Despite being obstructed by the Milky Way galaxy, its afterglow outburst outshone all other GRBs seen before. LHAASO detected several thousands very high energy photons extending up to 18 TeV. Detection of such energetic photons are unexpected due to the large opacity of the Universe. It is possible that in the afterglow epoch the intrinsic very high energy photon flux from the source might have increased manifolds, which could compensate the attenuation by pair-production with the extragalactic background light. We propose such a scenario and show that very high energy photons can be observed on the Earth from the interaction of very high energy protons with the seed synchrotron photons in the external forward shock region of the GRB jet.

2022

The timing of asteroidal impact events as revealed using the U-Th-Pb monazite dating

Date: 2022-12-30
Speaker: Garima Arora
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Impact cratering is one of the fundamental processes that modify surfaces of planets, satellites and asteroid bodies in our solar system. The precise and accurate dating of impact craters allows us the correlation of impact structure formation with other geological events (e.g. K-T extinction event). Additionally, impact cratering is also useful to infer the geological history and evolution including the Earth and rocky planetary bodies. The U–Th–Pb chemical dating of monazite using EPMA is a non-destructive, faster tool to decipher the timing of such extreme geological events. I will discuss about the principle and a few preliminary results based on impact-neo-crystallised monazite dating of terrestrial impactite. I will also discuss why this technique is novel and unique as compared to traditional age dating technique and its possible future implication.

SNS 2022: a summary

Date: 2022-12-30
Speaker: Prof. Navinder Singh
Venue: Room no: 469 (Main Campus)

Abstract

An informal discussion regarding the conference "Spectroscopies of Novel Superconductors (SNS 2022), 12th Dec to 16th Dec, Bangalore

A mechanical design and configuration optimization of the antenna and its deployment mechanism for the LIVE payload

Date: 2022-12-23
Speaker: Janmejay Kumar
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Designing a deployable V-antenna, within a limited mass budget, for the LIVE instrument is a very challenging task from a mechanical design perspective. A long antenna with a thin cross-section should be stiff enough to survive the launch environment. In this seminar, I will present configuration details and the working concept of the selected mechanism and antenna. I will discuss different forms of stowage of the V-antenna, like straight and folded antennas. These are studied from a natural frequency perspective. This involves a large number of design iterations and the results of the same shall also be discussed.

Observational dynamics of solar atmosphere : Spicules

Date: 2022-12-22
Speaker: Ravi Chaurasiya
Venue: USO Seminar Hall

Abstract

The chromosphere forms one of the atmospheric layers of the solar atmosphere, and it is complex and dynamic in nature, largely dominated by the local magnetic field configuration. Almost all of the mechanical energy that drives solar activity and solar atmospheric heating is converted into heat and radiation within this region. Chromosphere exhibits different dynamic phenomena; one of them is Spicules. In this seminar, I will discuss about spicules, their generation mechanism, properties and how these features can contribute to the mass supplying and coronal heating.

Radiative inclusive semileptonic $B$ decays

Date: 2022-12-20
Speaker: Dayanand Mishra
Venue: Room no: 469

Abstract

Inclusive semileptonic decays are dominated by quark-level transitions and are found to be theoretically cleaner than the exclusive decays. We investigate how the on-shell hard photon impacts an inclusive process, ie we study the process $B \to X_u \ell \nu){\ell}\gamma$. We calculate the decay width for the said processes using the Cutkosky rules considering the operators up to dimension five in the heavy quark effective theory, and find that there are no new operators generated in the calculation of the decay width, and it leads to similar non-perturbative matrix elements as present in the decay width of $B\to X_u \ell \nu_{\ell} $. Hence, it provides a cleaner determination of the two non-perturbative parameters: $\lambda_1$ (which provides information about the average spatial momentum squared of the heavy quark), and $\lambda_2$ (the amount of color magnetic field produced by the light cloud at the position of the heavy quark).

(a) Noble Gas Mass Spectrometer (NGMS): Challenges for Sample Analysis (b) Neon in Ordinary chondrites

Date: 2022-12-16
Speaker: Avadh Kumar
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

[a] NGMS at Thaltej campus is the multi-collector mass spectrometer for the measurement of isotopic ratios and concentrations of noble gases (He, Ne, Ar, Kr, and Xe) and nitrogen. Here discussion will be on how to deal with the malfunctioning of the instrument and the challenges in this instrument. [b] Ordinary chondrites (OCs) are the major flux of meteorites on Earth. They constitute ~80% of the total meteorites recovered. Neon isotopic ratios and concentration in ordinary chondrites are used to understand various insights in OCs. Here I am discussing neon data from bulk OCs. Isotopic ratios are used for deciphering the trapped components. While neon is also used to calculate the cosmic ray exposure age. Details will be discussed in the seminar.

Exploring the source region of 3-min slow magnetoacoustic waves observed in coronal fan loops

Date: 2022-12-09
Speaker: Ananya Rawat
Venue: USO Seminar Hall

Abstract

Sunspots host various oscillations and wave phenomena like umbral flashes, umbral oscillation, running penumbral waves, and coronal waves. All the coronal fan loops rooted in the sunspot umbra constantly show a 3-min period propagating slow magnetoacoustic waves. However, their origin in the lower atmosphere is still unclear. We studied these oscillations in detail along the clean fan loop system rooted in active region AR12553 for a 4-hour duration on June 16, 2016 observed by Interface Region Imaging Spectrograph (IRIS) and Solar Dynamics Observatory (SDO). We traced the footpoints of several fan loops at different atmospheric heights from the corona to the photosphere. We found presence of 3-min oscillations in the footpoints of all the loops at all the atmospheric heights. We traced the origin of these waves by utilising their amplitude and frequency modulation characteristics with time while propagating in the solar atmosphere. We found several modulation periods, such as 11 min, 19 min, and 30-35 min, in both amplitude and frequency modulations of these 3-min oscillations at all heights. Based on our findings, we interpret that 3-min slow magnetoacoustic waves propagating in the coronal fan loops are driven by 3-min oscillations observed at the photospheric footpoints of these fan loops in the umbral region. We also explored any connection between 3-min and 5-min oscillations observed at photospheric footpoints of these loops and found them to be weakly coupled. Results provide clear evidence of magnetic coupling of the solar atmosphere through the propagation of 3-min waves along the fan loops at different atmospheric heights.

From Quantum Optics to Bits and Pieces

Date: 2022-12-08
Speaker: Prof. Klaus Mølmer
Venue: Online ---> https://bluejeans.com/471795373/6057

Abstract

In this talk, I shall give a personally flavored account of the development of quantum optics starting with the simple, yet stunning, arguments applied by Roy Glauber to characterize temporal fluctuations in photo-detection signals. Such fluctuations can be signatures of non-classical properties, and the theory of photo-detection fueled the field of quantum optics with visions to prepare and apply a variety of quantum states of light and atomic light emitters in experiments. In the past decades, bits and pieces of solid-state materials were manufactured with high purity and precision, enabling observation of similar phenomena as we study with single atoms and photons in quantum optics. As a theorist I have worked with methods to describe the dynamics of open quantum systems, i.e., systems subject to interactions with their environment. I will show how these methods reintroduce, but with a plot twist, Niels Bohr’s quantum jumps in modern quantum physics. They also refine and elaborate on Glauber’s theories and while the original intent was to develop efficient theoretical and numerical methods that we can apply to quantum optics and solid-state bits and pieces, the same methods offer unique insights in physical dynamics and delightful encounters with the famous discussions between Niels Bohr and Albert Einstein on the interpretation of quantum theory.

Thermophysical Modeling for Planetary Science and KRC

Date: 2022-12-06
Speaker: Mr. Jayanth Serla
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Mechanical system configuration conceptualization & development philosophy for LIVE payload

Date: 2022-12-02
Speaker: Nirbhay Kumar Upadhyay
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The LIVE (Lightening Experiment for Venus Exploration) payload is a selected payload for the future Venus orbiter mission of India. The payload utilizes the electromagnetic signals, emitted by lightning events, for the detection of the same. The detection of the EM signal is achieved by a dipole V-antenna. As the antenna size is higher for stowage in the launch phase and for meeting the stiffness requirement, a deployment mechanism is needed. In this seminar, the various configurations and conceptualization of a deployable antenna system shall be presented for meeting the requirements of the payload. Also, the design philosophy for the payload development shall be briefly presented.

On the spectrum of colour sextet scalars in realistic SO(10) GUT

Date: 2022-12-02
Speaker: Saurabh Shukla
Venue: Room no: 469 (Main Campus)

Abstract

Incorporation of the standard model Yukawa interactions in a grand unified theory (GUT) often predicts varieties of new scalars that couple to the fermions and lead to some novel observational effects. We assess such a possibility for the colour sextet diquark scalars within the renormalisable models based on SO(10) GUT. Computing explicitly their couplings with the quarks, we evaluate their contributions to the neutral meson-antimeson mixing and baryon number-violating processes like neutron-antineutron oscillation. Moreover, pointing out a possibility of generating the observed baryon asymmetry of the universe with these scalar sextets, we constrain the mass of the sextets respecting several other constraints in realistic SO(10) GUTs.

The case of itinerant magnetism in CaMn2Al10: self-consistent renormalisation (SCR) theory study

Date: 2022-11-29
Speaker: Bharathiganesh D.
Venue: Room no: 469 (Main Campus)

Abstract

CaMn2Al10 is a novel Manganese(Mn) based magnetic system which by conventional wisdom based on Mn-Mn distance should be a magnetic insulator. But experiments on CaMn2Al10 have revealed several signatures of itinerant magnetism in this system. The Self Consistent Renormalisation (SCR) theory of itinerant magnetism is a powerful and very reliable tool for the study of itinerant magnetism. Hence explaining the experimentally observed results through the SCR theory would make us decisively conclude that the system CaMn2Al10 is an itinerant magnet. The talk will cover a broad overview of the SCR theory followed by our calculations for CaMn2Al10 system.

Photodiode: Characteristics and Applications

Date: 2022-11-18
Speaker: Sanjeev Kumar Mishra
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Silicon photodiodes are a class of semiconductor devices that respond to high energy particles and photons. Photodiodes operate by absorption of photons or charged particles and generate a flow of current in an external circuit, proportional to the incident power. While photodiodes have variety of applications, one prominent use is in the measurement of solar irradiance, especially in the ultraviolet range, due to their significance in dictating the photochemistry of the ionosphere of planets such as Mars and Venus. The talk will give an overview of photodiode, its characteristics and applications. It will discuss the electrical, optical, I-V characteristics. A brief discussion on the modes of its operation and the design of external circuit for the current measurement will also be discussed.

Photometric and topographic correction of Chandrayaan-2 IIRS (Imaging Infra-Red Spectrometer) data

Date: 2022-11-11
Speaker: Subhadyouti Bose
Venue: Online

Abstract

Photometric correction is a necessary step in planetary image pre-processing since the images of planetary surfaces are acquired by orbiting spacecraft at various observational geometries. One of the primary objectives of this proposal is to implement an empirical photometric correction for India's latest planetary hyperspectral sensor - Imaging Infrared Spectrometer (IIRS) - that has been sent to analyse the lunar surface onboard the Chandrayaan-2 mission. Photometric corrections have been proposed for the 800 to 2000 nm spectral range for data obtained from IIRS. The purpose of the proposed photometric correction for IIRS is to convert the observations taken at different solar incidence (i), sensor emission (e), and solar phase angles (α) to a fixed geometry by applying i = α = 30° and e = 0° to each image. The Lommel-Seeliger law will be used to correct the lunar limb darkening effect, while topography data from the merged Digital Elevation Model of Lunar Reconnaissance Orbiter - Lunar Orbiter Laser Altimeter (LRO-LOLA) will be utilised to correct for local topographic effects. In addition, data from Chandrayaan-1 Moon Mineralogy Mapper (M3) will also be used to compare radiance, reflectance and phase functions derived from IIRS. Preliminary analysis performed on IIRS data reveal that they are relatively darker as compared to M3 primarily due to significantly lower surface radiance values measured by IIRS. Derived phase functions for three IIRS bands (950, 1500 and 1700 nm) indicate a good correlation between (a) the derived reflectance and phase angle in the case of IIRS, (b) the phase functions derived for the empirically corrected M3 data, and (c) the surface reflectance values derived for IIRS and those of M3. In this talk, I will be discussing the need for performing photometric correction on IIRS data and the methodology that was followed to convert the data from radiance to reflectance and present some initial results after the application of a photometric function on IIRS data.

Distinguishing third generation scalar leptoquarks using top quark polarization

Date: 2022-11-11
Speaker: Debashis Saha
Venue: Room no: 469 (Main Campus)

Abstract

We study the effect of NLO QCD correction merged with parton shower on the distribution of polarization observables that are associated to the top quark polarization and examine the prospect of identifying the genesis of scalar leptoquark by looking into their pair production at the LHC. We study various angular and energy variables at the NLO+PS accuracy to distinguish scalar leptoquarks originating from different models and do multivariate analysis with jet-substructure variables to reach a higher discovery potential.

Investigation of Orbital Altitude Martian Dust Events and Its Origin

Date: 2022-11-09
Speaker: Jyotirmoy Kalita
Venue: Online

Abstract

The proposed work concentrates on the orbital level dust cloud in Mars, altitude ranging from 150 km to 1000 km from the Martian surface. These orbital level dust clouds may cause damage to the orbiting spacecraft during interaction. For, visual confirmation, the satellite imageries will be taken into consideration. For spectral confirmation, infrared and ultraviolet spectrograph will be consulted. Along with the confirmation of the presence of such clouds in the orbital level, further sounder and radar data will be consulted to understand the constituent of the cloud. The three point, 1. Mars surface origin 2. Mars moon origin 3. Space event origin will be analysed to understand these mysterious cloud at the orbital level, based on the time of occurrence, intensity of impact and relative atmosphere circulation influence of those events.

Three way interplay of strong correlations, topology, and disorder in high temperature superconductors

Date: 2022-11-09
Speaker: Dr. Debmalya Chakraborty
Venue: Room no: 469 (Main Campus)

Abstract

One of the major challenges in condensed matter physics is to understand how many interacting electrons form different phases of matter. One such exotic phase of matter formed solely due to the presence of interactions is superconductivity. Ever since their discovery, superconductors have found applications across diverse fields of science starting from medical science to high energy and astrophysics, apart from the long sought after applications, like lossless power transmission and magnetic levitation trains. The practical applicability of superconductors depends heavily on the temperature regimes where they exhibit superconductivity. It is largely believed that electron-electron interactions hold a key in achieving high superconducting transition temperatures. Recently, superconductors have been combined with topology to obtain topological superconductors with potential applications for topological quantum computation. Real-world materials bring in disorder as an additional important component. Taking an example of a high temperature superconductor, I will show how three way interplay of strong electronic correlations, topology, and disorder generates a new quantum phase of matter: a fully gapped "phase crystal" state that breaks both translational and time reversal invariance, characterized by a modulation of the d-wave superconducting phase co-existing with a modulating extended s-wave superconducting order. In contrast to conventional wisdom, this phase crystal state is remarkably robust to omnipresent disorder, but only in the presence of strong correlations, thus giving a clear route to its experimental realization. I will further discuss how understanding the roles of interactions, topology, and disorder can not only answer various existing unsolved puzzles, but also provide pathways to discovering new materials with novel functionalities.

On the origin of life-essential volatile elements on differentiated rocky bodies in the Solar System

Date: 2022-11-04
Speaker: Prof. Rajdeep Dasgupta, Maurice Ewing Professor of Earth Systems Science, Rice University, USA
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Long-term chemical habitability of rocky planetary surfaces rely heavily on the supply of life-essential, volatile elements from the interior. Therefore, the origin of carbon (C), sulfur (S), nitrogen (N), and hydrogen (H) budgets in the combined atmosphere-crust-mantle reservoir is key. Most studies to date approached the origin of major volatiles on Earth and rocky Solar System planets using isotopic fingerprinting of putative, undifferentiated building blocks and their comparison with terrestrial rocks. However, a critical step of planetary accretion, i.e., core-mantle-atmosphere differentiation for planetesimals, planetary embryos, and growing planets are often overlooked. In this talk, I will discuss some new observations both from laboratory experiments and meteorites to shed light on the origins and budgets of volatile elements in differentiated objects in our Solar System. A by product will be insights on the conditions and styles of rocky planet formation and growth that could likely lead to Earth-like rocky planets with their observed inventory of major volatiles.

Solar X-ray monitor onboard Ch-2: Inflight performance and the assessment of radiation damage of Silicon Drift Detector

Date: 2022-10-21
Speaker: Dr. M. Shanmugam
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The Solar X-ray Monitor (XSM) on-board Chandrayaan-2 mission is designed to carry out broadband spectroscopy of the Sun from lunar orbit. It measures the spectrum every second in the soft X-ray band of 1 to 15 keV with an energy resolution better than 180 eV at 5.9 keV. Though the XSM measurement will aid in quantitative interpretation of elemental composition of the Moon by the companion instrument Chandra’s Large Area Soft x-ray Spectrometer (CLASS), but the XSM observations can independently be used to study the Sun as well. The Chandrayaan-2 mission was launched on 22 July 2019, and the XSM began nominal operations, in lunar orbit, from September 2019. The in-fight observations, so far, have shown that its spectral performance has been identical to that on the ground. XSM detected several M-class flares and it has been demonstrated that the XSM is sensitive enough to detect solar activity well below A-class and also micro flares. We also made a provision onboard to measure the radiation damage to the SDD. In this seminar, the detailed onboard performance assessment will be presented.

Multi wavelength study of solar activities and KASI programs for Heliophysics

Date: 2022-10-20
Speaker: Dr. Kyung-Suk Cho
Venue: USO Seminar Hall

Abstract

Key Aspects of EFTs

Date: 2022-10-19
Speaker: Dr. Jacky Kumar
Venue: Room no: 469 (Main Campus)

Abstract

In this talk, I will give details on the important technical aspects of the EFTs that are relevant for particle physics phenomenology and are often used in my work. In particular, I will discuss the advantages of using EFTs as compared to the full theory, EFTs at tree-level and 1-loop, matching, renormalization scheme dependence, renormalization group running (RGE) in the context of Delta F=1 and 2 flavour violating processes.

Explorations of physics at different scales

Date: 2022-10-18
Speaker: Dr. Jacky Kumar
Venue: Room no: 469 (Main Campus)

Abstract

In particle physics we try to probe nature at very small distance scales. Currently, the Standard Model (SM) of particle physics is the most successful model that can explain many of the observed phenomena. In 2012, the last missing piece of the SM, the Higgs Boson was discovered. Still, the SM can not be a complete theory of nature due to various reasons, so physics beyond it must exist. However, contrary to our expectations no other new particles have been found. Therefore, the scale of new physics (NP) might be much above the electroweak (EW) scale ~ 100 GeV. Interestingly, the scale hierarchies allow us to construct an effective field (EFT) which can be used to describe physics below a certain scale without knowing about the full ultraviolet theory, up to a certain approximation. Historically, the Weak effective theory (WET) was of great importance in the development of the SM. I will argue that, in the same way, the scale gap between the EW and the NP scale allows us to construct the EFTs which can serve as testing grounds for NP in the coming years, in a model independent fashion. In this context, I will highlight my recent work on the development of such EFTs, their phenomenological applications as well as computer tools to automate the phenomenological calculations using such EFTs.

Title 1.: Formation and evolution of Ryugu asteroid ; Title 2.: Modelling electric permittivity of pure-ice and ice-rock mixtures; implications for detection of ice on Moon

Date: 2022-10-14
Speaker: Prof. Debabrata Banerjee
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

A novel approach to radiation detector readout system for space-borne instrumentation

Date: 2022-10-07
Speaker: Arpit Patel
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Typically, the charge-sensitive preamplifier converts the small charge signal from the semiconductor-based detector into voltage form, and the signal is then amplified to measure the energy of the incoming radiation. A shaping amplifier reduces the signal bandwidth by amplifying the voltage pulse from a charge-sensitive preamplifier (CSPA). Precision measurement of the peak amplitude of shaping amplifier output is required for improved energy resolution. The available PHA methods are power, mass and area consuming and also difficult to implement in Field Programmable Gate Arrays for multiple detector systems. In FPGA, a new method based on LaGrange's interpolation is used to precisely measure the peak of an analogue pulse. The results show that the new method provides comparable energy resolution to available PHA methods. The new approach and available PHA methods will be discussed in detail in the seminar.

TPC #5: Weber’s Electrodynamics

Date: 2022-09-29
Speaker: Prof. A. K. T. Assis
Venue: Online ---> https://osachapter.zoom.us/j/96972643322?pwd=VjBZdHNkTCtsVFM2YVdGZDk0QlRYdz09

Abstract

We present the origins of Weber’s electrodynamics (1846). Weber’s force depends not only on the distance between the interacting charges, but also on their relative velocity and relative acceleration. We discuss Ampère’s force between current elements and compare it with Grassmann-Biot-Savart’s law. We also compare Lorentz’s force with Weber’s force. We present Weber’s planetary model of the atom. It was developed before Rutherford’s experiments and Bohr’s model. In Weber’s planetary model, the positive nucleus is stabilized (or held together) by purely electrodynamic forces. According to Weber, when two positive charges are very close to one another, they behave as if they had a negative inertial mass, attracting one another instead of repelling each other. We discuss applications of Weber’s electrodynamics to superconductivity. We also present modern experiments and theoretical developments related to Weber’s electrodynamics.

A scotogenic $S3$ symmetric model for realistic neutrino mixing and generation of small yukawa couplings naturally from trans-Planckian asymptotic safety

Date: 2022-09-22
Speaker: Dr. Soumita Pramanick
Venue: Online ---> https://bluejeans.com/876239449/7355

Abstract

In the first segment of the talk I will discuss a scotogenic neutrino mass model at one-loop level based on discrete flavour symmetry $S3\times Z_2$. The model has two right-handed neutrinos. These two right-handed neutrinos when are maximally mixed, we can yield the form of the left-handed Majorana neutrino mass matrix with $\theta_{13}=0$ and $\theta_{23}=\pi/4$. Realistic mixing in agreement with the neutrino oscillation data i.e., non-zero $\theta_{13}$, deviation of $\theta_{23}$ from maximality and small corrections to solar mixing angle $\theta_{12}$ could be obtained by tweaking the maximal mixing between the two right-handed neutrino states by a small amount. The model has two $Z_2$ odd inert $SU(2)_L$ doublet scalars, the lightest among which can serve as a dark matter candidate. In the second segment of the talk we will focus on generation of arbitrarily small Yukawa couplings naturally due to the presence of a non-interactive infrared-attractive fixed point for gauge-Yukawa systems in trans-Planckian asymptotic safety framework. Together with the non-interactive infrared-attractive fixed point, more ultraviolet-attractive fixed points are also present in the system that ensure well-defined nature of the theory at infinitely high scale. This technology was used for a system of Yukawa couplings of the Standard Model extended by three right-handed neutrinos, for which asymptotically safe solutions for Dirac neutrinos satisfying the experimental constraints on neutrino masses and mixing for Normal Ordering were found. With the help of this general mechanism, feeble Yukawa interactions needed to produce the correct relic density via freeze-in for sterile-neutrino dark matter models can also be generated naturally.

Condensed dark matter with a Yukawa interaction

Date: 2022-09-20
Speaker: Dr. Raghuveer Garani
Venue: Online ---> https://bluejeans.com/298697694/1725

Abstract

I will discuss about the possible phases of a condensed dark matter (DM) candidate taken to be in the form of a fermion with a Yukawa coupling to a scalar particle, at zero temperature but at finite density. This theory essentially depends on only four parameters, the Yukawa coupling, the fermion mass, the scalar mediator mass, and the DM density. At low fermion densities we delimit the Bardeen-Cooper-Schrieffer (BCS), Bose-Einstein Condensate (BEC) and crossover phases as a function of model parameters using the notion of scattering length. I will further discuss in some detail the BCS phase by consistently including emergent effects such as the scalar density condensate and superfluid gaps. Within the mean field approximation, the consistent set of gap equations are derived, retaining their momentum dependence, and valid in both the non-relativistic and relativistic regimes. I will present numerical solutions to the set of gap equations, in particular when the mediator mass is smaller and larger than the DM mass. Finally, I will conclude with a few comments on the equation of state (EoS) and possible astrophysical implications for asymmetric DM.

Effects of magnetic fields on the propagation of gravity waves in the solar atmosphere

Date: 2022-09-19
Speaker: Mr. Hirdesh Kumar
Venue: USO Seminar Hall

Abstract

Gravity waves in the solar atmosphere are now increasingly recognised as an important contributor to the dynamics and energetics of the lower solar atmosphere. Their characteristic negative phase-shift over height, while propagating energy upwards, is a well recognised observational signature. Since their first detailed observational detection and estimates of energy content, a number of studies have explored their propagation characteristics and interaction with magnetic fields and other wave modes in the solar atmosphere. Recently, numerical simulations have shown that gravity waves are suppressed or scattered and reflected back into the lower solar atmosphere in the presence of magnetic fields. In order to investigate the propagation characteristics, we utilize intensity observations that cover photospheric to chromospheric heights over different magnetic configurations of quiet-Sun (magnetic network regions), a plage, and a sunspot as well as velocity observations within the photospheric layer over a quiet and a sunspot region. We construct two-height intensity - intensity and velocity - velocity cross-spectra and study phase and coherence signals in the wavenumber -frequency dispersion diagrams and their association with background magnetic fields. In this talk, I will discuss the signatures of association between magnetic fields and much reduced phase shifts over height from intensity-intensity and velocityvelocity phase and coherence diagrams both indicating suppression/scattering and reflection of gravity waves by the magnetic fields and thereby provide a qualitativeobservational verification of numerical simulations of such phenomena.

TPC #4: Superconductivity: A phenomenon with many facets

Date: 2022-09-15
Speaker: Prof. Krishnendu Sengupta
Venue: oNLINE ---> https://osachapter.zoom.us/j/96615620484?pwd=RjE5aDBzaUh0VFpyVk9ESExTcEc1UT09

Abstract

In this talk, I shall provide a pedagogical introduction to the history of superconductivity. This will be followed by a discussion of unconventional superconductors and their phenomenology. I shall conclude with a brief discussion of unanswered questions and possible future directions.

Li-Be-B systematics in time-varying early forming solar system objects

Date: 2022-09-09
Speaker: Vikram Goyal
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Chondrites, the most primitive meteorites, preserve chronological information of the Solar System formation that took place ~4.56 Ga ago. Major constituents of chondrites include Calcium-Aluminium-rich Inclusions (CAIs) followed by AOAs and Chondrules. These have been dated to have formed within the first few million years of solar system formation and thus preserve a record of the earliest stages of the Solar System formation. Al-Rich Chondrules(ARCs) are special as they contain high abundance of corundum (>10%); corundum being a refractory mineral, it petrologically links two other major chondritic components, ferromagnesian chondrules (FMCs) and CAIs (supposedly, first forming solids). We know, short-lived radionuclides (SLN) are radioactive nuclei having a very short half-life compared to the age of the solar system. Study of origin of the few specific SLNs can impose a stringent constraint on the early solar activities. In this talk, I will discuss Li-Be-B systematics, an important system in the studies of short-lived radionuclides. Because of its very short half-life of just 53days, the measurement of 7Be confirms the presence of the irradiation process and also puts constraints on the early solar activity. Here, we discuss the importance of studying various early forming solids (in chronological order) to build Solar activity profile for first few million years.

From Ocean Science to Blue Economy<img src='/prl-eng/images/red.gif'>

Date: 2022-09-07
Speaker: Dr. Shailesh Nayak
Venue: ONLINE

Abstract

The ‘Blue Economy’ has been defined as an ocean-dependent economic development to improve quality of life of people while ensuring inclusive social development as well as environmental and ecological security. India has been committed to advance the “Blue Economy” and several programs have been initiated to promote blue economy in the country. The knowledge about seabed, marine mineral and energy resources, fishery resources, natural hazards in the Exclusive Economic Zone (EEZ), legal continental shelf (LCS) as well as High Seas is a pre-requisite for growth and development. The marine fish catch is about 3.7 million tons for last several years. The exploration of deep-water fishery indicated availability of about 3.3 million tons. Many new grounds of fishery between 200-2000 m have been identified. The technological challenges of harvesting, post-harvesting and processing for product development must be undertaken for commercialization of deep-sea fishery. Geophysical and bathymetric surveys of the EEZ, LCS and High Seas have provided information about placer minerals on the coast and nearshore waters, gas hydrates on continental shelf areas as well as manganese nodules, hydrothermal systems, and cobalt crusts in High Seas. The investment in developing technologies for harnessing these resources has been made as a part of ‘Deep Sea Mission.’ Similar investment needs to be made in developing human resources. The resultant increase in anthropogenic activities on the coast along with impacts of climate change will affect the environment and ecology of the coastal zone. The coast is also vulnerable to many hazards such as cyclones, storm surges, tsunamis, coastal erosion, sea level rise, etc. The managing coastal zone for ensuring ecological and livelihood securities along with advancing developmental activities is a challenge. The coastal and marine spatial mapping including coastal vulnerability should be used to understand risks involved, and accordingly, developmental activities should be planned. Regular satellite-based monitoring of coastal ecosystems is a vital requirement of such planning. There is now consensus that macro-economic decisions about the blue economy will need environmental data. The economic growth prospects in the ocean beyond 2030 will be limited without large investments to support ocean environments. We need to develop a framework to bring together disparate data sources by developing an accounting system for oceans. Lastly, we need to set up an institutional framework for implementing activities related to blue economy. We need invest in building infrastructure, human resources, finances, and governance system. Such investments in sustainable development of oceans will pay rich dividends for future generations for the benefit of humanity.

Volcano-tectonic landforms in Tharsis and their interaction with fluvial activity: a terrestrial analogue perspective

Date: 2022-09-02
Speaker: Dr. Anil Chavan
Venue: Online

Abstract

Volcanism in Tharsis region of Mars induced radial faulting which also lead to the formation of grabens and wrinkle ridges. Volcanism separates all the tectonic phases in the Tharsis region, hence inter-relation between the volcanic and tectonic landforms is critical to understand the evolution of Tharsis and associated landforms. The high-resolution images may provide ample opportunity to identify the reactivation of the ancient faults in context with the tectonic activity. The low shield volcano in close proximity to Tharsis and volcanic cones observed on the peripheral parts of the Deccan traps has close resemblance and thus brings the need for their comparison and exploration. The inter-relation of volcanic cones with the tectonics and their spatial distribution can be deciphered by nearest-neighbour (N-N) analysis (orientation with respect to each other). The large number of valley networks on the Tharsis bulge was active during the Noachian–Hesperian epoch which probably influenced the shift from phyllosilicate to sulfate formation conditions. The hydrous minerals can be confirmed by using compositional datasets along exposed walls of grabens associated with Tharsis, similar to interbedded red bole beds in deccan traps. The combined studies of geomorphology and mineral context will help focus on future exploration sites with the prospective signature of water and life in the Tharsis region of Mars.

TPC #3: Classical gravitational radiation from soft theorem.

Date: 2022-09-01
Speaker: Prof. Ashoke Sen
Venue: Online ---> https://osachapter.zoom.us/j/99386217848?pwd=NDJqdjFvdzZUd2xhelAxUFlPOENLQT09

Abstract

We shall discuss how some properties of scattering amplitudes in quantum gravity can be used to derive properties of classical gravitational radiation emitted during astrophysical processes.

Quantum Oscillations in Nodal-line semimetals

Date: 2022-08-30
Speaker: Dr. Satyaki Kar
Venue: Room no: 469 (Main Campus)

Abstract

Nodal line semimetals (NLSM) exhibit interesting quantum oscillation characteristics when acted upon by strong magnetic fields. We consider a NLSM continuum model to report the features of the Landau level spectra and the fluctuations in the Fermi level as the field in a direction perpendicular to the nodal plane is varied through. Based on the results on parallel magnetization, we demonstrate the growth of quantum oscillation with field strength as well as its constancy in period when plotted against 1/B. We find that the density of states which show series of peaks in succession, witness bifurcation of those peaks due to Zeeman effect. For field normal to nodal plane, such bifurcations are discernible only if the electron effective mass is considerably smaller than its free value, which usually happens in these systems. Though a reduced effective mass m∗ causes the Zeeman splitting to become small compared to Landau level spacings, experimental results indicate a manyfold increase in the Lande g factor which again amplifies the Zeeman contribution. Interestingly, topologically nontrivial oscillations are witnessed at low energies when the magnetic field lies in the nodal plane. There the density of state peaks do not repeat periodically with energy anymore. The spectra become more spread out and the Zeeman splittings become less prominent. We find the low energy topological regime, that appears with such in-plane field set up, to shrink further with reduced m∗ values. However, such topological regime can be stretched out in case there are smaller Fermi velocities for electrons in the direction normal to the nodal plane. Moreover, an oscillatory field variation, as opposed to a steady one, has interesting impact on the quantum oscillation phenomena with the Landau tubes crossing the Fermi surface extremally two times per cycle. With proper parameters chosen, one can engineer topological transitions to occur periodically in such systems as an in-plane oscillating field is swept through its cycles.

Phase transitions and critical phenomena in a disordered Potts model

Date: 2022-08-29
Speaker: Dr. Manoj Kumar
Venue: Online ---> https://bluejeans.com/709008545/1460

Abstract

In this talk, I’ll speak about the phase transitions and critical features in a three-state random field Potts model (RFPM) in three dimensions. Considering a universal feature that the phase transition in such models is governed by a zero-temperature random fixed point, we target the problem by determining the ground states at temperature T = 0. Finding ground states however in RFPM is known to be NP-hard. We make use of a computationally efficient graph cut algorithm to determine excellent approximate ground states in P time. From such states, various quantities like magnetization, Binder-cumulant, specific heat, susceptibility, are evaluated and extrapolated in the limit of quasi-exact ground states. These results are obtained for different system sizes and an extensive finite-size scaling approach is implemented to estimate the critical point and the exponents that characterize the singular behavior near the transition.

Latest Results from New Horizons: Interplanetary Dust Observations up to 50 AU

Date: 2022-08-26
Speaker: Jayesh P Pabari
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Interplanetary Dust Particles (IDPs) exist everywhere in our solar system. In the inner solar system, IDP is mainly expected to be originated from Asteroid belt and occasionally, from comets. On the other hand, IDP in outer solar system is expected from (Edgeworth) Kuiper belt also; however, its knowledge had been limited. The New Horizons spacecraft has provided observations of dust during its journey to Pluto and beyond. The speaker will cover the latest results of IDP up to 50 AU from Sun and, reveal the dust distribution in solar system.

TPC #2: Many-body Localization: Recent Advancements and Puzzles

Date: 2022-08-18
Speaker: Prof. Arti Garg
Venue: Online --> https://bluejeans.com/954548701/2310

Abstract

The physics of Anderson localization in non-interacting disordered quantum systems has been a cornerstone of condensed matter theory. Turning on interactions in these disordered systems results in the many-body localized (MBL) phase where the system lacks transport up to a finite temperature. In this talk I will review recent advancements in the field of MBL, both, on theoretical and experimental sides followed up by the open questions and problems. I will also mention some of our recent works on MBL which have helped to characterize the MBL phase and resolved the long standing issue about the stability of the MBL phase in the presence of long range interactions.

Volcanism, crustal cooling and impact history of the differentiated asteroid Vesta through the lens of the 40Ar/39Ar technique

Date: 2022-08-18
Speaker: Prof. Fred Jourdan, Head of Discipline: Geology, Director of the Western Australian Argon Isotope Facility, School of Earth and Planetary Sciences, Curtin University, Perth WA6845
Venue: Online

Abstract

Based on 40Ar/39Ar analyses of different components (mineral, matrix, melt) of HED meteorites, the history of volcanism, crustal cooling and impact history will be elucidated.

Self-interacting dark matter and related phenomenologies

Date: 2022-08-17
Speaker: Dr. Manoranjan Dutta
Venue: Online --> https://bluejeans.com/954548701/2310

Abstract

The Standard Model of Cosmology or the ΛCDM model, where DM is postulated to be cold and collisionless is in excellent agreement with the large-scale structures of the Universe. However, at small scales (most prominently at the scale of dwarf galaxies), there are several discrepancies between the astrophysical observations and the predictions of the ΛCDM model, leading to small-scale anomalies such as `cusp-core problem', `missing satellite problem' and `too-big-to-fail problem'. To alleviate these small-scale anomalies, self-interacting dark matter (SIDM) was proposed in 2000. SIDM particles have very large self-interaction among themselves with a scattering cross-section of O(10-24 cm2/GeV), which is many orders of magnitude larger than the typical WIMP cross-section of O(10-38 cm2/GeV). Moreover, the favoured cross-section scale decreases gradually from dwarf to cluster scale and eventually matches with ΛCDM predictions at a large scale, hinting towards a velocity-dependent self-interaction cross-section. In the light of these inadequacies of the ΛCDM model and since the Standard Model (SM) of particle physics fails to provide a viable DM candidate, I will discuss a few beyond the Standard Model (BSM) scenarios capable of explaining SIDM and related phenomenologies like the tiny neutrino mass. I will discuss both elastic and inelastic self-scattering of DM via a light mediator through Yukawa-type potentials, while neutrino phenomenology involves the popular seesaw variants.

Radiatively generated fermion mass hierarchy from flavour non-universal gauge symmetries

Date: 2022-08-11
Speaker: Gurucharan Mohanta
Venue: Room no: 469 (Main camp)

Abstract

A framework based on a class of abelian gauge symmetries is proposed in which the masses of only the third generation quarks and leptons arise at the tree level. The fermions of the first and second families receive their masses through radiative corrections induced by the new gauge bosons in the loops. It is shown that the class of abelian symmetries which can viably implement this mechanism are flavour non-universal in nature. Taking the all-fermion generalization of the well-known leptonic $L_\mu-L_\tau$ and $L_e - L_\mu$ symmetries, we construct an explicit renormalizable model based on two $U(1)$ which is shown to reproduce the observed fermion mass spectrum of the Standard Model. The first and second generation fermion masses are loop suppressed while the hierarchy between these two generations results from a gap between the masses of two vector bosons of the extended gauge symmetries. Several phenomenological aspects of the flavourful new physics are discussed and lower limits on the masses of the vector bosons are derived.

TPC #1: Evolution of Modern Science in India

Date: 2022-08-04
Speaker: Prof. Sreerup Raychaudhuri
Venue: Online --> https://osachapter.zoom.us/j/96118620386?pwd=cnNZcUJyekZTR3JJOEc4aExQTFQ2UT09

Abstract

In this non-technical talk, the history and evolution of modern science in India will be broadly surveyed. After a brief introduction, the introduction of scientific processes by the British will be mentioned, and followed by a description of the spread of western education in India. The contributions of pioneering Indian scientists in the colonial period will then be described. Finally, the growth of major scientific and technological institutions in post-independence India will be outlined.

The Impact of Impact

Date: 2022-08-04
Speaker: Prof. Dr. Philippe Claeys, Head of the Analytical, Environmental and Geochemical Research Group, VUB, Brussel
Venue: Online

Abstract

This presentation covers the identification of evidence to support a large meteorite impact at the Cretaceous-Paleocene boundary (K-Pg) 66 million years and the discovery and recent drilling of the Chicxulub crater in Yucatan. It also discusses how this major planetary collision triggered a rapid and brutal global environmental change that led to the demise of the non-avian dinosaurs and fauna and flora on Earth.

Characterisation of ChaSTE probe under simulated Lunar Environment

Date: 2022-07-29
Speaker: Peddireddy Kalyana Srinivasa Reddy
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

ChasTE - Chandra’s Surface thermo-physical Experiment is an instrument on-board the Chandrayaan-2/3 Lander. It is aimed at measuring the in-situ Thermo-physical properties of the top 10cm of the lunar soil. During the experiment, the probe is deployed into the lunar soil at the landing site and the temperature sensors on the probe provide in-situ temperature profile. These temperature measurements are further interpreted to derive the Thermal Diffusivity and Thermal conductivity of the lunar soil. A proper characterisation is essential for correct interpretation of the measured temperatures. These characterisation experiments are carried out on a ChaSTE lab setup under simulated lunar environment. For this purpose, we have augmented the existing facility to replicate a realistic ChaSTE scenario to carry out the experiments. I will be talking about the details of these experiments in further detail, new developments and some experimental results.

Infrared Spectroscopy for the BepiColombo Mission to Mercury

Date: 2022-07-28
Speaker: Dr. Andreas Morlok , niversity of Münster, Institut für Planetologie, Münster
Venue: Online

Abstract

Mercury, the innermost planet of the Solar System, is characterized by a heavily cratered surface, a lare core and a strong magnetic field. It was rarely visited by space probes, the ESA/JAXA mission to Mercury arriving in 2025 is only the third visit so far. Onboard is a suite of instruments allowing to investigate Mercury in high detail. This talk will focus on the MERTIS instrument. MERTIS (Mercury Radiometer and Thermal Infrared Spectrometer) will allow to map most of the hermean surface in the mid-infrared, a spectral region so far not covered in earlier missions. With the help of the expected data, the surface composition and mineralogy of Mercury will be determined in detail for the first time. The presentation will be about our work at the IRIS laboratory in Münster, where we conduct laboratory measurements for the interpretation of the expected result.

Insight into the geological processes of Posidonious crater and around it

Date: 2022-07-22
Speaker: Kimi Khungree Basumatary
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Several lunar craters witnessed magmatism and tectonic modification processes. Craters with the signatures of earlier (e.g. magmatism) activities and recent tectonic (e.g. grabens, wrinkle ridge, lobate scraps) activities will bridge the past and recent activities. The Posidonius crater, centred at 32⁰ N, 30⁰ E and located on the north-eastern rim of the Mare Serenitatis, is one such crater which archived the geological activities that occurred on the Moon. The Posidonius crater is a mare filled, floor fractured crater (FFC) with slumped walls. It has wrinkle ridges and lobate scarps resulting from tectonics thrust faulting. It also contains extensional features such as grabens and collapsed features such as pits. In this study, we mapped such features and did chronological studies using high-resolution images from Lunar Reconnaissance Orbiter (LRO). For the compositional study, we used Moon Mineralogy Mapper (M3). We observed that features such as rilles, grabens, wrinkle ridges, lobate scarps and pits are dominant in the western part of the Posidonius craters and its region. Rilles are plausibly collapsed features, and small-scale grabens, not associated with contractional features (wrinkle ridges and lobate scarps), are plausibly latter effects of collapsed rilles. We observed slumping along the southern and eastern crater walls, and mare resurfaced the western floor. In this presentation, I will discuss the different geological activities that occurred within and around the Posidonius crater.

Channels Connected to Craters (C^3) on Mars

Date: 2022-07-15
Speaker: Vijayan S.
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Mars host features like valleys, channels, and fan/delta deposits which provide evidence for its past water-rich history compared to present-day dry and cold conditions. In addition, the numerous craters present on the surface had interacted with these channels. A large number of valley-channel networks associated craters with fluvial deposits on Mars provide an unprecedented opportunity to explore its past hydrological conditions. This interaction of crater and channels is an interesting region where the water related activities are recorded within the crater. Such craters are the potential target site for the past and future landing mission to Mars. In this talk, channels connected to craters (C^3) will be discussed in detail and will provide new locations on Mars. The C^3 is of different types for example the channels can be within the crater walls or the channels/valleys from outside the crater rim. Both the scenarios are present on Mars and they reveal the diverse water related activities that prevailed on Mars and how it varied over geological timescale will be discussed in this talk.

Improved Constraints on Effective Top Quark Interactions using Edge Convolution Networks

Date: 2022-07-14
Speaker: Dr. Akanksha Bhardwaj
Venue: Room No. 469 (Main Campus)

Abstract

In this talk, we will discuss the potential of Graph Neural (GNNs) to improve the performance of high-dimensional effective field theory parameter fits collider data beyond traditional rectangular cut-based differential distribution analyses. We will focus on a SMEFT analysis of pp→tt production, including top decays, where the linear effective field deformation is parametrised by thirteen independent Wilson coefficients. The application of GNNs allows us to condense the multidimensional phase space information available for the discrimination of BSM effects from the SM expectation by considering all available final state correlations directly. The number of contributing new physics couplings very quickly leads to statistical limitations when the GNN output is directly employed as an EFT discrimination tool. However, a selection based on minimising the SM contribution enhances the fit's sensitivity when reflected as a (non-rectangular) selection on the inclusive data samples that are typically employed when looking for non-resonant deviations from the SM by means of differential distributions.

A Time-Line for the Formation of Terrestrial Planets

Date: 2022-07-07
Speaker: Prof. Klaus Mezger, Institute of Geological Sciences and Center for Space and Habitability, University of Bern, Switzerland
Venue: Online

Abstract

Chemical and isotopic analyses of primitive meteorites reveal that the building blocks of the rocky planets in our solar system are derived from different nucleosynthetic sources. These diverse materials were mixed at an early stage and provided the matter that ended up in the solar system bodies. The path from a gas-dust cloud to the final arrangement of the planets in our solar system took several 10s of million years and involved different processes, including condensation and evaporation, melting, collision and differentiation of planetesimals, impacts and metamorphism. A specific, and possibly unique, sequence of events and processes led to the formation of the Earth, the only known planet that brought forth life and sustained it for billions of years. Information on the early evolution of the solar system is stored in meteorites and their components and also can be reconstructed from the bulk composition of planets, particularly the Earth. A key piece of information for a good understanding of the dynamic evolution of our own planetary system is the timing of different physical and chemical processes and events in the early solar system. To this end geochronological information from meteorites needs to be combined with their chemical and isotopic composition.

Volcanism and Tectonism in the Mare Marginis and Smythii region of the Moon

Date: 2022-07-01
Speaker: Neha Panwar
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Mare Marginis (13.3°N, 86.1°E) is a small mare located north of the Smythii Basin (1.3°N, 87.5°E) at the eastern nearside - farside boundary. It is not known to be formed as a result of a basin filling volcanic episode as no topographic or gravity signatures reflective of a basin are observed in the region. Several large craters in the region have excavated material from different depths within the crust, thus profiling it. Since, the craters in the region are not completely filled with mare basalts, they also provide a unique opportunity to study the early stages of mare volcanism on the Moon. Mare Marginis and the Smythii Basin also have a system of arcuate wrinkle ridges running through them. Wrinkle ridges are contractional landforms found on the surface of lunar maria. These are complex thrust fault systems primarily formed as a result of compressional stresses from local basin related tectonics as well as global lunar tectonics. Previous studies have displayed that the relationship between the displacement (Dmax) and length (L) of fault populations can be used to infer the long-term stress field prevalent in a region. The Dmax-L relationship has been used for the wrinkle ridges to compute the contractional strain within this region. The study aims at using the data from Moon Mineralogy Mapper (M3) onboard Chandrayaan-1 alongside the topography data to understand the geomorphology and mineralogical composition, and tectonic setting of the region and how it compares with the other major mare in the region (e.g., Mare Australe).

Experimental and Theoretical Study of Non-Linear Optical Crystals

Date: 2022-07-01
Speaker: Dr. Mitesh Solanki
Venue: Online ---> https://bluejeans.com/108520645

Abstract

One of the most often used nonlinear optical materials is Potassium Dihydrogen Phosphate (KDP). Growth in slow solvent evaporation at room temperature has resulted in high-quality Alkali (Li, Rb and Cs) doped KDP crystals grown. When studying the structure of formed crystals, it was discovered that they were single-phasic and had only modest variations in their unit cell characteristics. During the Retvield refining, the role of dopant was studied. This technique was used to study the linear optical characteristics of formed crystals, such as the optical transparency energy band gap; reflectance; extinction coefficient; refractive index; etc. When doping KDP crystals, the Kurtz and Perry powder NLO approach was used to investigate the nonlinear optical improvement that occurred. It was used to conduct an a.c. electrical investigation of generated crystals. The Generalized Gradient Approximation pseudopotential approach has been used in the theoretical investigation like band structure, density of state elastic constant, optical properties and phonon dynamics of single crystals produced.

Tin stable isotope variations in natural materials: Implications for planetary and nebular processes

Date: 2022-06-30
Speaker: Dr. Dipankar Pathak, Isotopengeologie Gruppe, Institut für Geologie, Universität Bern, Bern, Switzerland
Venue: Online

Abstract

The mass dependent isotope variation in volatile elements could act as useful proxies to understand the early solar system conditions, where materials processed through evaporation and condensation in the solar nebula was eventually incorporated by planetesimals during their accretion. The isotope composition of H and O, in a water molecule are subjected to modification during such physico-chemical processes, and hence it is difficult to readily extract information from them with less uncertainty. Tin being a moderately volatile element could be used to trace the origin of volatile components in a terrestrial planet like Earth. Due to a unique geochemical behavior of being both chalcophile and siderophile, Sn also additionally enables understanding the core formation process of Earth using iron meteorites and high P-T experimental products, as proxies. A novel wet chemistry based methodology was developed to provide these answers by precisely measuring stable Sn isotope variations in terrestrial and meteorite samples using a double spike MC-ICP-MS technique. Given the significance of such volatile elements, I will present the challenges in developing analytical methods for measuring Sn isotopes, and some results obtained from analyses of few terrestrial and chondrite samples.

COVID 19 in India - Opportunities & Challenges<img src='/prl-eng/images/red.gif'>

Date: 2022-06-29
Speaker: Dr. Raman R. Gangakhedkar
Venue: ONLINE

Abstract

This talk will discuss how the Government has handled the Covid 19 pandemic in India since its inception. How lockdown helped us to prepare better to mitigate the health outcomes. The talk will also deliberate on the future course of the pandemic, vaccination, and key challenges that continue to exist.

Development of an SDD based Large Area X-ray Spectrometer with ASIC readout for future planetary mission

Date: 2022-06-24
Speaker: Nishant Singh
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Silicon drift detector-based X-ray spectroscopy has been employed for applications varying from solar studies, XRF experiments, X-ray imaging to various astronomical observations. We propose developing a multi-detector large area X-ray spectrometer using Silicon Drift Detectors (SDD) for X-rays in the energy range of 500 eV to 15 KeV. Using discrete components for the application will lead to a bulky system and hence the miniaturized system is desired. In this direction, we propose to develop the spectrometer using Application-Specific Integrated Circuit (ASIC) based readout which can process the signal from multiple detectors simultaneously. The VERDI ASIC reads out the signals from 8 independent detectors with controllable thresholds, shaping time and gains for each channel. The characterization and the performance of the ASIC will be discussed in the seminar.

Cwebs beyond three loops in multiparton amplitudes

Date: 2022-06-23
Speaker: Mr. Sourav Pal
Venue: Online

Abstract

The correlators of Wilson-line operators are fundamental objects for the study of the infrared properties in QCD and other non-abelian gauge theories. In perturbation theory, they are known to exponentiate, and their logarithm can be organized in terms of collections of Feynman diagrams called webs. In this talk, I will discuss some recent results regarding their organization at higher perturbative orders, determination of the colour structures that contribute to the soft anomalous dimension, and a new method of constructing the web mixing matrices.

Design of Optical Filters for Solar Observations

Date: 2022-06-23
Speaker: Ms. S. Parvathy
Venue: USO Seminar Hall

Abstract

Hot Spring Mineral Assemblage on Earth: Implication and Linkage to Mars

Date: 2022-06-17
Speaker: Subham Sarkar, SAC Ahmedabad
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Hot spring localities on continents may represent the most likely locales for the formation of early life components on Earth. Apart from liquid water, an oxygenated atmosphere and carbohydrates, these components also include elements like boron that are crucial for stabilization of the complex organic molecules that constitute life. In this Context, characterization of the complete mineralogical assemblage of the Puga hot spring deposit, Ladakh, India, using detailed spectroscopic and X-ray diffraction studies have been done. This study has an importance for future detection of similar mineralogical assemblage on Mars using state of the art instruments on-board Perseverance Rover. Future work using various instruments of the Perseverance rover will be helpful for search for biosignature on Mars (which is one of the major science objective of the Rover mission). Earth based analog studies hold a key for future sensor development and finally for identification and characterization of the related minerals on Mars.

Primordial noble gas component hosted by water-susceptible materials in less-altered CR chondrites

Date: 2022-06-16
Speaker: Dr. Tomoya Obase, Hokkaido University, Japan.
Venue: Online

Abstract

Previous studies of noble gases in primitive meteorites have focused primarily on acid-resistant phases that contain most of the noble gases in the primitive meteorites. However, a new Ne-rich noble gas component hosted by water-susceptible materials was recently found in some aqueously less-altered CR chondrites. In this seminar, I will talk about the potential relationship between the Ne-rich materials in CR chondrites and cometary materials. The talk also briefly introduces basic knowledge of noble gases in primitive meteorites and why noble gases are unique tracers in cosmochemistry.

Beyond Standard Model : A left-right theory approach

Date: 2022-06-16
Speaker: Dr. Chayan Majumdar
Venue: Online --> https://bluejeans.com/495767101/4803

Abstract

In spite of being a successful theory, the Standard Model (SM) has several shortcomings. All these limitations of the SM give a clear hint of Beyond SM (BSM) physics and Left-Right (LR) theories are one of the successful BSM scenarios to provide a unified explanation to the origin of small neutrino mass and low-energy parity violation in weak phenomenology. The spontaneous breakdown of LR symmetry to SM can be achieved via the vacuum expectation values (vevs) of either (i) bidoublet + triplet Higgs, or (ii) bidoublet + doublet Higgs or (iii) combination of both (i) and (ii). We have considered such several variants of Higgs sectors in LR symmetry and studied certain phenomenological and cosmological signatures of these frameworks. Moreover, another approach to conventional LRSM, aka, ALRM can evade unavoidable FCNC constraints naturally. We have explored one of such ALRMs where we have studied the possibility of having significant contribution to neutrinoless double beta decay as well as low-scale leptogenesis.

Disorder, strong correlations and unconventional superconductors

Date: 2022-06-14
Speaker: Dr. Vivek Mishra
Venue: Ground floor lecture hall

Abstract

Unconventional superconductivity is one of the key areas of research for past several decades, either due to high transition temperatures or due to exotic superconducting states with novel topological properties. Most of the unconventional superconductors are intrinsically dirty. They carry lots of impurities, therefore, relevant to this discussion is disorder that always exists in these systems. Here I will review the seminal work by Abrikosov and Gorkov that is widely used to understand the disorder effects in superconductors. I will then discuss the limitation of the Abrikosov-Gorkov theory in the case of electronic pairing. I will present some of my new results showing the effect of strong correlation on impurity scattering in d-wave superconductors that are relevant for cuprates. I will also discuss the implications of realistic impurities

Isotopic variations of Carbon and Nitrogen in IAB iron meteorites

Date: 2022-06-10
Speaker: Sourajit Sahoo
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The process of formation of IAB iron meteorites is still unclear, and many hypotheses have been put forward to explain the unique trace elemental and morphological trends in them. Hf-W ages after GCR correction suggest that, IAB parent body accreted about 3-5 Mya post CAI’s, which is old for widespread melting by 26Al nuclides, but makes impact melting a strong candidate. Our analysis was carried out on Kendall County meteorite sample mapped under SEM and analysed for δ13C under the Camera nano-SIMS 50. Graphite shows a range of different morphologies, in different host phases within the metal matrix. We made carbon isotope measurements on graphite, inside Troilite (FeS) and Schreibersite (Fe3P) and the metal matrix Kamacite/Taenite (Fe-Ni alloy) and also the metal surrounding the graphites. Our data conforms to the presence of unequilibrated primitive δ13C in graphites ranging from 4‰ to -21‰. We simulated two models based on Fast cooled kinetic fractionation and Rayleigh fractionation method respectively and tried to compare our data to these simulations. Using the simulated data and SIMS data we discuss the various parameters that might be influencing the δ13C of IAB irons, the petrology of the graphites and draw conclusion about the early solar system.

New Insights into Glaciation and Gully Formation in the Mid-latitudes of Mars: A remote sensing perspective

Date: 2022-06-03
Speaker: Rishitosh K. Sinha
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Late Amazonian geological history of mid-latitudes of Mars is dominated by a suite of landforms that substantiate geologically recent surface – atmosphere exchange of ice. In our study, we have investigated two of the most popular landforms: glaciers and gullies. We have used remote sensing datasets to examine the role they have played in modification of the Mars’ surface during the past few million years to hundreds of millions of years. Our observations and analysis have revealed (1) Glaciers and gullies, both common in the mid-latitudes, have been spatiotemporally related as implied by glaciation, followed by cyclic emplacement and removal of LDM cover, and subsequent formation of gullies on surfaces with and without LDM/glacial deposits. (2) The unique morphological and morphometric characteristics of alcoves and fans that we report on here do present evidence for a widespread occurrence of recent terrestrial debris-flow like process on Mars. (3) The nature of interaction between glaciers, LDM and gullies does present reasonable evidence for extensive presence of ice in their formation. However, both CO2 and H2O ices are often found in vicinity. While CO2 ice sublimation keeps the gullies active in the present-day, debris-flow process still stands out as the dominant mechanism of sediment transport in Martian gullies in the past epochs. In the seminar, I will discuss these findings and present a geological evolutionary model of Mars during the Late Amazonian.

How hot and wet is the Moon: Insight from experiments

Date: 2022-06-02
Speaker: Dr. Ananya Mallik, Assistant Professor, (The RealReal Inc. Endowed Chair in Gem Science), Department of Geosciences, University of Arizona, Tucson, Arizona, USA
Venue: Online

Abstract

The thermal profile of the Moon (selenotherm) is required to determine its present-day interior structure and composition, and yet it is not constrained well. How can we constrain the selenotherm better? Also, measurements on lunar samples indicate that the Moon is not ‘bone dry’ but does have some hydrogen in its interior. The bulk lunar hydrogen is an important constraint to understand the dynamics of the Moon-forming impact as well as determine the origin of volatiles in the Earth-Moon system. The estimates of bulk lunar hydrogen span across a few orders of magnitude, but how can we constrain it better? In this talk, I will discuss how we can better estimate both the thermal state and the bulk lunar hydrogen to improve our understanding of lunar evolution.

Modelling studies on the formation of organic molecules in the cometary atmosphere

Date: 2022-05-27
Speaker: Sana Ahmed (SRF-PSDN)
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Comets are made up of frozen volatile ices that are largely unprocessed material surviving from the early Solar System. Cometary volatiles have been detected both in situ, and by remote observations of the cometary atmosphere or coma. At present, a total of 72 volatile species have been identified in comets, including tentative detections, out of which 37 are organic molecules. Some of the complex organics that have been observed include ethanol, acetaldehyde, methyl formate, the N-bearing organics formamide, acetonitrile and cyanoacetylene, and the diols ethylene glycol and glycolaldehyde. It has not yet been proven that all of the molecules identified in the coma of comets originate from the frozen ices inside the cometary nucleus. Comets showing moderate to high activity can reach sufficient coma densities for molecules to form by active gas-phase coma chemistry. Thus, it is pertinent to study the coma chemistry, with an emphasis on the gas-phase pathways that create organic molecules in a cometary coma. We selected a sample of four Oort cloud comets in order to study the formation of organics in their gas-phase comae. These comets are, in chronological order of their discovery, C/1996 B2 (Hyakutake), C/2012 F6 (Lemmon), C/2013 R1 (Lovejoy) and C/2014 Q2 (Lovejoy). We have used a combined chemical-hydrodynamical multi-fluid coma model for our study. The governing equations for the model are a set of coupled first-order differential equations, obtained from the conservation of number density, mass, momentum, and energy. In this seminar, I will give a discussion on organic molecules in comets, and present our model results on the formation of various organic species by gas phase coma chemistry.

The Terrestrial Impact Record

Date: 2022-05-26
Speaker: Prof. Christian Koeberl, University of Vienna, Austria, Austrian Academy of Sciences
Venue: Online

Abstract

The recognition of impact craters on the Earth is difficult, because active geological and atmospheric processes on our planet obscure or erase the impact record in geologically short time periods. For the confirmation of impact craters on Earth, detailed mineralogical, petrographic, and geochemical studies are needed. Nevertheless, about 200 terrestrial impact craters have been identified. On Earth, the first impact evidence exists in the form of various spherule layers in South Africa and Australia, aged between about 3.4 and 2.5 Ga. The oldest preserved impact structures have ages of 2.02 and 1.86 Ga. Thus, there is little information about the impact record and its effects during the first 2.5 billion years of Earth history, but it is clear that then and later, impacts had severe effects on the geological and biological evolution on Earth.

Aqueous alteration of CM chondrites

Date: 2022-05-20
Speaker: Shivani Baliyan, SRF, PSDN
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

CM, Mighei-like carbonaceous chondrites, have experienced variable degrees of aqueous alteration. Like alteration, CMs exhibit variable degrees of brecciation: some samples are unbrecciated, and some are highly brecciated. Brecciation destroys the original texture of the meteorite; therefore, understanding the setting and nature of aqueous alteration in the CM parent(s) is difficult. CM chondrites are primitive solar-system materials that experienced aqueous alteration at low temperatures, resulting in the formation of secondary minerals, including phyllosilicates, tochilinite, and carbonates. Phyllosilicates could be present as the matrix in the meteorite or as fine-grained rims around the chondrules. However, tochilinite generally occurs as intergrowths with cronstdetite, known as TCIs. Carbonates are usually seen as small grains (generally, 20-80 µm) within the matrix but are sometimes also reported as veins. In this talk, I will be discussing the condition, degree, and episodes, of aqueous alteration in CM chondrite & also some local changes concerning different ionic activities in the secondary minerals formed during aqueous alteration.

Mars - A short history through time

Date: 2022-05-19
Speaker: Dr. Stephanie C. Werner, Professor of Geophysics and Planetary Sciences, Centre for Earth Evolution and Dynamics, Department of Geosciences, University of Oslo
Venue: Online

Abstract

The presentation will introduce the main geological processes acting on Mars, which are typical and common on Earth-like planets. Furthermore, it will provide insight into the geological evolution of Mars based on remote-sensing data. Using meteorites from Mars, one can extract detailed information on the rocks and minerals, as well as temporal constraints. Globally, sequencing of events relies on crater statistics. While Mars now appears to be rather a cold desert, in the past water has been more abundant. This is evident in martian morphology and mineralogy. Exploration of Mars with the help of spectral analyses indicate surface weathering and mineral formation that requires water. The different atmosphere composition, however, challenges simple transfer of process details from Earth to Mars. Nevertheless, Earth rocks and terrestrial analogue studies and experiments improve understanding Mars' evolutionary history.

Unique regolith characteristics of the Reiner Gamma swirl as revealed by imaging polarimetry

Date: 2022-05-13
Speaker: Dr. Megha Upendra Bhatt
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The Reiner Gamma swirl located in the western part of Oceanus Procellarum is a prototypical example of a lunar swirl, corresponding to an irregular marking associated with a local magnetic anomaly and showing no topographic relief. A systematic study of regolith properties of the Reiner Gamma swirl with respect to the surrounding mare carried out based on phase ratio images and imaging polarimetry. We acquired a total of 20 data sets of Reiner Gamma between January 05th and March 05th, 2021, at Mount Abu Observatory using the CCD-based Electron Multiplying Optical Imaging Polarimeter (EMPOL) with GC (green) and RC (red) narrow-band continuum filters. The covered range of phase angles is between 7 and 106 degrees. I will present results obtained by adapting the Hapke model to the phase ratio images. Our analyses suggest that the surface roughness, opposition effect strength, and median grain size of the Reiner Gamma regolith differ from those of the surrounding mare surface indicating a disruption of the surficial regolith microstructure in the swirl area. These findings are consistent with an external mechanism of swirl formation such as by interaction between the regolith and the gaseous hull of a passing comet.

Aqueous alteration of primitive meteorites

Date: 2022-05-12
Speaker: Dr. Wataru Fujiya, Associate Professor, Faculty of Science, Ibaraki University, Japan
Venue: Online

Abstract

Evidence for aqueous alteration can be found in essentially all chondrite groups and is pronounced in CI, CM, and CR chondrites. The aqueous alteration played an important roll in material evolution on water-rich planetesimals and thus an understanding of water activity is crucial to investigate how volatile materials including ice and organic matter were modified from their original forms in planetesimals before their delivery to terrestrial planets. In this seminar, I am talking about pristine materials in chondrites and how they were transformed by aqueous alteration in their parent bodies. I am focusing on the timing and the conditions such as temperature and water to rock ratios of the aqueous alteration. I will also raise a few unsolved questions about aqueous alteration for future research directions.

Noachian Volcanism: Implication to the thermo-chemical evolution of early Mars

Date: 2022-05-06
Speaker: Alka Rani (SRF-PSDN)
Venue: Hybrid mode

Abstract

Mars has been volcanically active throughout its history from Noachian to the Late Amazonian. Martian volcanic provinces are of great geologic interest as the composition of igneous rock formed from the eruption of magma tends to preserve the record of thermal properties viz. pressure, temperature, or degree of partial melting at which it forms. Earlier studies focused on Hesperian to Amazonian depict the evolved magmatism, which is compatible with systematic compositional variations over time, showing cooling of mantle and thickening of the lithosphere. However, the type and style of Noachian-aged volcanism remain unknown. This study aims to develop a perspective of spatiotemporal changes in the interior, emphatically of the Noachian Mars. In this talk, I will discuss compositional variability among Noachian provinces and its implication for the thermo-chemical evolution of early Mars.

Thermal alteration of CM chondrites: Mineralogical changes and metamorphic temperature

Date: 2022-05-05
Speaker: Dr. Ashley King, Future Leader Fellow,UK Research and Innovation, Department of Earth Sciences, Natural History Museum, UK
Venue: Online

Abstract

Most CM chondrites experienced only low temperature (<300C) aqueous alteration in the early solar system. However, a number also record an episode of post-hydration thermal metamorphism at temperatures up to 1000C. Remote observations suggest that such materials may be common on the surface of primitive asteroids. We are therefore investigating the mechanism, timing, and duration of metamorphism in CM chondrites to better understand the thermal history of volatile-rich asteroids and provide context for samples returned from Ryugu and Bennu by the Hayabusa2 and OSIRIS-REx missions.

Biogeochemical aspects of atmospheric methane

Date: 2022-05-02
Speaker: Ms. Akanksha
Venue: Ground Floor Lecture Hall

Abstract

Short lived climate forcers (SLCFs) alter the Earth’s radiative balance and perturb other components of the climate system (cryosphere, clouds, water cycle). SLCFs like black carbon aerosols and CH4 arethe leading contributors to climate change, after CO2. To the total CH4 emissions during 2008-17 (576 Tg/y, top-down), wetlands and biomass burning have contributed nearly 32% and 5%, respectively. Modelling studies predict the increase in microbial activity in wetlands with increasing temperatures thus increased CH4 emissions. Further, biomass burning emissions are projected to increase with land-use change. This emphasizes a need for a coherent understanding of interactions and feedback processes in atmosphere-land-ocean. Role of biogeochemical cycles involving methane and tools to study them will be discussed.

Predictive understanding of the Indian monsoon in a changing climate<img src='/prl-eng/images/red.gif'/>

Date: 2022-04-27
Speaker: Dr. Krishnan Raghavan, FASc, FNA
Venue: ONLINE

Abstract

There is unequivocal evidence that human-caused global warming has been the main driver of the observed intensification of heavy precipitation over the land regions across the globe, which is further projected to enhance with additional warming during the 21st century (IPCC AR6 WG1, 2021). While it is recognized that increasing anthropogenic emissions of greenhouse gas (GHG) and aerosols have influenced monsoon precipitation changes over South and East Asia since the second half of the 20th century, there is considerable spread in the monsoon precipitation projections across climate models. This talk will provide a brief summary of the observed and projected changes in the Indian / South Asian monsoon based on the recent IPCC AR6 WG1 report (2021), discuss the sources of uncertainties and future research for reducing uncertainties in the monsoon projections. In particular, the talk will highlight the importance of “predictive understanding” of regional monsoon phenomena required for improving the representation of monsoon processes (especially convection) and simulations of monsoon precipitation (mean, variability and extremes) in state-of-the-art climate models.

Importance of air-sea exchange of reactive trace gases over the northern Indian Ocean

Date: 2022-04-25
Speaker: Ms. Mansi Gupta
Venue: Ground Floor Lecture Hall

Abstract

Reactive trace gases play an important role in atmospheric chemistry and climate change in the Earth's atmosphere. One such category of reactive trace gases is volatile organic compounds (VOCs). In addition to terrestrial sources, the emission from global oceans is a significant source of many reactive trace gases via exchange across the air-sea interface. Ocean water is an important source of light non-methane hydrocarbons (NMHCs), oxygenated VOCs, dimethylsulfide (DMS), and halogenated VOCs in remote marine atmosphere. The transfer of trace gases from both the water- and air- sides is driven by several physical processes that can modulate the kinetics of flux across the interface. Along with physical processes, the exchange is also controlled by a concentration gradient at the interface driven by chemical and biological processes. In most studies, the air-sea fluxes of trace gases have been estimated using a diffusive sublayer model. The production of reactive trace gases in seawater is dependent on both biotic and abiotic mechanisms. However, major biogenic VOCs (isoprene and DMS) are predominantly produced by phytoplankton and microbial activity. The high biological activity of the northern Indian Ocean makes it an important region to be investigated for the production and emission of reactive trace gases. I will discuss the processes controlling air-sea exchange and their importance, along with the methodology of identification and quantification of NMHCs and DMS in the marine atmosphere.

Isotopic investigation of insoluble organic matter in CMs- A NanoSIMS study

Date: 2022-04-25
Speaker: Shreeya Natrajan
Venue: Online

Abstract

The majority of carbon and nitrogen abundances found in chondrites is usually associated with macromolecular organic component. The fraction of this component that survives acid demineralization is termed as “insoluble” organic matter (IOM). The 13C and 15N isotopic ratios measured in IOM extracted from carbonaceous chondrites generally show large enrichments. These provide clues to the origin, formation and the effects of nebular and parent body processing on the organic matter. Nitrogen isotopic anomalies manifest as both 15N rich and poor signatures, called as hotspots and coldspots respectively.15N anomalies of the order of ~2000–3000‰ and - 400‰ have been reported in carbonaceous chondrites. The enrichments termed as hotspots are speculated to be a result of ion molecule reactions at very low temperatures in the outer portion of the nascent solar nebula or the ISM. Alternatively, these enrichments can also be explained by UV irradiation self-shielding similar to that of oxygen, self-shielding model indicating they could have occurred in the outer solar nebula. The local ISM and several molecular clouds show depleted nitrogen isotopic ratios. Moreover, the solar value of δ15Nair~ -380 ‰ calculated based on the data from Genesis and atmospheric composition of Jupiter also indicated a lower abundance of 15N. In this talk I will be discussing the case for both nebular and ISM origin of organic matter based on their carbon and nitrogen isotopic heritage using data from Nano SIMS analysis.

The Effect of Metallicity on the Composition of Exoplanet Atmospheres

Date: 2022-04-22
Speaker: Vikas Soni (SRF-PSDN)
Venue: Hybrid mode

Abstract

Exoplanets exhibit a wide range in their parameter space, including equilibrium temperature, radius, mass, orbital properties, and metallicity, which can alter the exoplanet atmospheric composition. Atmospheric metallicity is one such parameter that affects the atmospheric equilibrium abundance, chemical conversion time scales, and the location of the quench level. The effect of metallicity on the equilibrium abundance has a rich discussion in the literature. However, the impact of metallicity in the presence of transport is poorly constrained. We have used the quenching approximation to understand the same in the current work. We have constructed a tool to study the conversion pathways in the chemical network. We ran a series of chemical equilibrium models to make a 3D grid in the temperature, pressure, and metallicity space. First, we studied the effect of metallicity on the equilibrium abundance, and then we used our tool to see the impact of metallicity on the quench level. In this presentation, I will talk about the quench approximation and how we use this to analyze the effect of metallicity in the exoplanetary atmosphere in the presence of transport.

Disorder, strong correlations and unconventional superconductors

Date: 2022-04-21
Speaker: Dr. Vivek Mishra
Venue: Online --> https://bluejeans.com/758381390/4420

Abstract

Understanding Planetary Differentiation from Hf-W systematics

Date: 2022-04-21
Speaker: Dr. G. Srinivasan, Bhopal
Venue: Online

Abstract

The source of one of the largest group of differentiated planets (asteroid 4 Vesta) is a differentiated planet with a metallic core. Meteorites from this asteroid collectively referred to by acronym HEDs (howardite, eucrite, and diogenites) provide a valuable avenue for studying evolution of rocky terrestrial planets. These small rocky bodies arrested in different stages of evolution, preserve information about processes that have been erased on larger planets due to their prolonged activity. Differentiated silicate rich meteorites are depleted siderophile elements while Fe meteorites are rich rich in these elements. The homogeneous oxygen isotope composition support large scale melting event on the planetary body resulting in a metallic core and a silicate mantle, very much like Earth, Moon and Mars. I will explore the elemental distribution of W in these silicate rich meteorites and 182Hf-182W isotope systematics to constrain the process of planetary differentiation.

Chiral limit of QCD: interests and relevance

Date: 2022-04-18
Speaker: Dr. Anirban Lahiri
Venue: Online --> https://bluejeans.com/478390705/7319

Abstract

I would like to start with the features of the phase diagram of QCD in the physical world, where the pion has mass equal to its PDG value. Next I want to add one dimension in that diagram in terms of light quark masses and discuss how the previously discussed phase plane for the physical world is embedded in a more global structure and I will discuss the various aspects of this global phase diagram. After setting the stage I would like to focus on the behavior of the Polyakov loop towards the chiral limit of QCD. On contrary to the folklore that the Polyakov loop can be treated as a pseudo-order parameter of deconfinement for finite quark masses, we showed that the Polyakov loop is essentially sensitive to the chiral transition for physical and smaller than physical quark masses and behave as an energy-like observable w.r.t. the chiral phase transition.

Recent works on suprathermal populations and calibration data analysis of STEPS-ASPEX

Date: 2022-04-18
Speaker: Mr. Bijoy Dalal
Venue: Ground Floor Lecture Hall

Abstract

Using 22 years’ of suprathermal particle measurements from the L1 point by the ACE satellite, we have recently brought out the differences in the variations of different (particularly helium and iron) suprathermal populations in solar cycle 23 and 24. Although these results throw light on the possible roles of First Ionization Potential (FIP) and mass to charge ratio (M/Q) dependences of the energization processes, it is also realized that directionally resolved suprathermal particle measurements can be very helpful in understanding these processes. Suprathermal and Energetic Particle Spectrometer (STEPS), a sub-system of the Aditya Solar wind Particle Experiment (ASPEX), on board the upcoming Aditya-L1 satellite will measure suprathermal particles from six directions. These unique, directional measurements might provide important insights on these energization processes that have been elusive so far to the scientific community. STEPS has gone through various test, evaluation and calibration processes. In this talk, I will discuss how the calibration data are being analyzed and incorporated in the data pipelining software to get the desired science data.

Enhancements in Helium abundance in Interplanetary Coronal Mass Ejections

Date: 2022-04-11
Speaker: Mr. Yogesh
Venue: Ground Floor Lecture Hall

Abstract

The relative abundance of alpha particles with respect to protons (AHe=(nα/np) *100) is 8-8.5% in the photosphere. However, AHe varies from 2-5% in the solar wind depending on the solar activity level and solar wind velocity. Interestingly, AHe can increase significantly and reach above 8% in the interplanetary coronal mass ejections (ICME) passing through the first Lagrangian point (L1) of the Sun-Earth system. To understand the AHe enhancement in ICMEs, we have carried out a detailed investigation using database spanning over two solar cycles. We show that there is a solar activity variation of ICME averaged AHe values. Further, we evaluate the role of various factors like the first ionization potential (FIP) effect, localized coronal heating, chromospheric evaporation, gravitational settling etc. for the variation of AHe beyond 8% in ICMEs. The insights obtained from these investigations will be presented.

Petrogenesis of lunar meteorite A-881757: insight into early thermo-chemical evolution of the Moon

Date: 2022-04-08
Speaker: Yash Srivastava (SRF-PSDN)
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Understanding of chemical and thermal evolution of the Moon has been the focus of considerable attention over the past five decades. Mare basalts returned by Apollo, Luna, and Chang’E missions gives us information of the lunar interior evolution. Typically understood, Lunar basalts are formed by the partial melting of the mantle, with heating assisted by the mixing of heat-producing incompatible element-rich layers known as “KREEP”. However noteworthy that most of these basalts are obtained from locations at or near the PKT region. Therefore, it is suggested that our present knowledge of chemical and thermal evolution could be biased by limited spatial and temporal sampling. Lunar meteorites offer us to study the other regions on the Moon which is otherwise inaccessible. In this talk, I shall briefly highlight our results for lunar meteorite Asuka-881757, which is distinct from returned samples. Further, I will discuss its petrogenesis and implication on the early chemical and thermal evolution of the Moon.

The Ancient Climate of Mars: Was the Ambient Climate 'Warm and Wet' or 'Cold and Icy'?

Date: 2022-04-07
Speaker: Dr. Jim Head, Professor of Earth, Environmental, and Planetary Sciences (Research), Brown University
Venue: Online

Abstract

One of the most fundamental questions in planetary science today is the nature of the ambient climate of early Mars (Noachian-Early Hesperian): Was the ambient climate “warm and wet”, as suggested by widespread phyllosilicates, higher erosion rates, enhanced crater degradation, valley networks, and open/closed-basin lakes? Or was the ambient climate “cold and icy”, as suggested by recent climate models, with occasional perturbations causing heating and melting of surface snow and ice, and runoff to produce the observed characteristics and features? Using the framework of these two ambient climate options, we will discuss outstanding questions and how these might be resolved. We will also explore the roles of the NASA Mars 2020 mission to the Jezero Crater open-basin lake, and the CNSA Tianwen-1 mission to Utopia Planitia in addressing these issues.

Exploring strongly interacting matter with small quark masses

Date: 2022-04-07
Speaker: Dr. Anirban Lahiri
Venue: Online --> https://bluejeans.com/271773288/2243

Abstract

Exploration of the phases of the strongly interacting matter under extreme conditions has been a topic of immense discussion over the last decades. Attempts have been made both from theoretical and experimental workfronts like ALICE@LHC, STAR@RHIC and CBM@FAIR and plenty of others, to understand the phases and transitions between them. Chiral symmetry breaking and confinement are the two most important effects in the non-perturbative domain of Quantum ChromoDynamics (QCD) which is the field theoretic description of the strongly interacting matter, in the theoretical perspective. In this talk I will discuss the features of QCD towards the vanishing value of light quark masses, the so-called chiral limit. Starting with an introduction to the QCD phases in the physical world I will continue with some new results towards the chiral limit calculated using the lattice framework of QCD and various salient features related to the critical behavior that can be realized through our latest calculations.

Controllable long-range entanglement in a lossy qubit array

Date: 2022-04-04
Speaker: Dr. Shovan Dutta
Venue: Online --> https://bluejeans.com/242229952/8151

Abstract

Environmental noise typically drives a quantum system to a unique steady state with little quantum correlations, which is a major obstacle for quantum information processing. I will talk about a simple experimental setting of an array of two-level systems with localised environmental noise that has multiple highly coherent steady states, including maximally-entangled states of nonlocal (Bell) pairs. Such states originate from a hidden symmetry that conserves these pairs over long distances, leading to controllable long-range entanglement. I will discuss how to selectively prepare and observe these states in present-day many-body atomic/photonic setups.

Atmospheric chemistry over India: Integrating measurements with photochemical box model

Date: 2022-04-04
Speaker: Ms. Meghna Soni
Venue: Ground Floor Lecture Hall

Abstract

Atmospheric chemistry over the Indian region significantly influences the air composition and climate over regional to global scale. Nevertheless, studies on detailed air chemistry particularly related with biogenic emissions, radicals, and halogens remain lacking. In this regard, we included state-of-the-art in situ measurements and satellite data into photochemical box model to study the chemical evolution of air downwind of Ahmedabad. The model simulation shows a large build up in O3 (∼115 ppbv) and numerous secondary inorganics (e.g., nitric acid ∼17 ppbv) and organics (e.g., ketones ∼11 ppbv). The noontime maximum levels of hydroxyl (OH) and hydroperoxyl (HO2) radicals are simulated to be 0.3 and 44 pptv, respectively. Volatile Organic Compounds are the major OH sink initially but contribution of CO is greater on the further days. Model output infused into air trajectories shows outflow of ozone-rich air towards the Arabian Sea, in agreement with measurements and a global model. An observational curve between isoprene and air temperature was included in the model to assess the possible effect of warming on ozone. Further, satellite-derived trend in leaf area and chemistry of key halogens are being included in model to unravel their impact on the oxidation capacity of atmosphere.

Meteorites from Morocco: An overview

Date: 2022-04-01
Speaker: Prof. Hasnaa CHENNAOUI AOUDJEHANE, Faculty of Sciences Ain Chock FSAC, Department of Geology, Casablanca MOROCCO
Venue: Online

Abstract

An overview of meteorites from Morocco will be given in this talk. Meteorites are extraterrestrial rocks. They are crucial not only to the apparition of water and life on Earth but also to the mass extinction of species. Meteorites are mostly found in cold deserts such as Antarctica and hot ones such as Oman, Sahara and Chili. The Sahara, and especially the Moroccan one, provides a significant number of meteorites for researchers and collectors all over the world.

Phyllosilicate on Mars: Observation from outcrop to microscopic scale

Date: 2022-04-01
Speaker: Aditya Das (JRF-PSDN)
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Throughout its geological history of 4.5 Ga Mars has experienced a sharp transition from a warm and wet climate during the Noachian era to a cold and dry climate during the Amazonian. Thus, this warm and wet climate was conducive for the formation of clays (phyllosilicates) by the aqueous alteration of the primary minerals. Global spectroscopic surveys through remote sensing and in situ analyses by rover missions have confirmed the presence of such clays throughout the Martian Surface most of which are of Noachian age. Thus, it is imperative to understand the process of formation of such clays with its stratigraphy since the process of formation leading to such stratigraphy is under constraint. Therefore, terrestrial analog that nearly represents the Martian surface is taken for analysis of the clay stratigraphy formation - the Deccan Continental Flood Basalt owing to its hotspot type of volcanism like Mars. Microscopic level analysis of clays was done by using Nakhlite meteorite that has appreciable amount of aqueous alteration which is seen by the presence of iddingsite, laihunite. Since, crystallization age as well as the aqueous alteration age for the Nakhlites is reported to be in the late Amazonian era which was water starved we still find the presence of clays with a unique association of Carbonates and sulphates which forms in antagonistic conditions. The reason for such association is not very well defined. Therefore, detailed analysis needs to be done to understand this unique association.

Lower moments of nucleon parton distribution functions (PDFs) in lattice QCD

Date: 2022-03-31
Speaker: Dr. Santanu Mondal
Venue: Online --> https://bluejeans.com/206075327/5345

Abstract

In this talk, I will first introduce parton distribution functions and discuss their phenomenological importance. Then I will describe our recent first-principle calculations using lattice QCD (Phys. Rev. D102 (2020) no.5, 054512 and JHEP 04 (2021) 044, JHEP 21 (2020) 004) of the first x-moment of nucleon isovector polarized, unpolarized and transversity distributions. We use the standard method for the calculation of these moments (via matrix elements of twist two operators) and carry out a detailed analysis of the sources of systematic uncertainty, in particular of excited state contributions. Finally, I will describe my future plans in this direction and in a different direction (composite Higgs models on the lattice).

Comparative study of Climatic Changes and Volcanism on Earth and Extraterrestrial Bodies

Date: 2022-03-25
Speaker: Dr. K.S. Misra
Venue: Online Platform (Bluejeans)

Abstract

Probing the First Billion Years of our Universe with 21-cm radiation from neutral hydrogen.

Date: 2022-03-24
Speaker: Dr. Raghunath Ghara
Venue: Online --> https://bluejeans.com/942367125/7939

Abstract

The redshifted 21-cm signal from the intergalactic medium (IGM) neutral hydrogen is the most promising probe of the Epoch of Reionization. It has the ability to reveal many of the unknown facts about this epoch such as properties of the early sources of radiation, thermal and ionization states of the IGM. Radio telescopes such as LOFAR, MWA, HERA are providing stronger upper limits on the 21-cm power spectrum. I will be talking about this probe and how these measurements are used to infer the states of the IGM as well as the properties of the first sources that formed during that period.

Geological investigation of boulder-fall activity in the Vitello crater region on the Moon

Date: 2022-03-11
Speaker: Rishitosh Kumar Sinha
Venue: Online

Abstract

Boulder-falls are mass wasting features that produce trails consisting of boulder sliding, rolling, and bouncing on the steep slope surfaces. Over the past decade, a number of studies have found morphological evidence of lobate scarps in the vicinity of the boulder-fall trails, thus related to shallow moonquake-induced ground shaking responsible for triggering boulder-falls during the past ~50 to few million years. Additionally, recent impact induced ground shaking has been also inferred to have triggered boulder-falls. Although there has been no consensus on the fundamental idea that which process dominates boulder-fall activity on the lunar surface. In this regard, we use the Chandrayaan-2 TMC-2, LRO NAC/WAC, and Kaguya TC datasets to investigate the state of boulder-fall activity in the previously unexplored Vitello crater (~42.5 km, centered at 30.4° S, 37.5° W) region comprising of 17 craters. Our observations reveal that: (1) Vitello crater hosts evidence of one of the largest (~45 m in length) boulder-fall ever happened on the Moon (totally 460 boulder-fall trails in the crater central portion), (2) removal of the darkened, mature regolith on steep slopes leads to the exposure of boulders from beneath, (3) the impact craters that were found to host boulder-falls on their walls lack bright ejecta and rays and therefore craters are supposedly older than the boulder-fall trail, (4) this region hosts unique evidence of recent ‘impact-ejected’ boulder-fall trails in the crater ejecta, (5) both lobate scarps and grabens are evident in the vicinity of the boulder-fall trail sites, and (6) lobate scarps cross-cut impact craters consistent with boulder-falls on their walls. To address the important question of the potential triggering mechanism, we investigate the geological setting of the Vitello crater region. The Vitello crater is situated at the southern rim of Mare Humorum basin, and hosts a complex network of concentric and radial fractures on the crater floor. Additionally, our investigation revealed evidence for lobate scarps on the crater floor and elongated fractures exposed in the Vitello crater walls. Apart from a recent ~400 m recent bright rayed impact crater in the region and localized boulder-falls, we have not found evidence for impact-induced boulder-falls in the region. Therefore, the possibility of boulder-falls consistent with the shallow moonquake-induced ground shaking is higher in this region. Furthermore, we have found that the localized small-scale lobate scarps are aligned in the same direction to the regional main scarp evident in this region. Moreover, the fracture exposed in the Vitello walls connects to the Humorum basin-related graben system that crosscuts the main scarp. Additionally, the walls of the main scarp and the impact craters (considerably old) formed over the main scarp both hosts’ extensive boulder-falls. Graben walls also witnessed extensive boulder-falls. Therefore, we propose that the possibility of ground shaking triggered by late-stage activity associated with the structurally pre-existing weak zones along the main scarp and regional graben in the interior of this region on the Moon cannot be excluded as the primary triggering mechanism for one of the largest (and unique) boulder-fall on the Moon and for boulder-falls in more than 10 craters out of 17 craters in the study region. Potential new evidence of volcanic vents along the graben exterior walls and boulder alignment along the vents supports this notion. Recent impact events only trigger localized boulder-falls. Taken together, the study reveals geological evidence of significant late-stage tectonic activity in this region of the Moon, thereby suggesting that the late-stage contractional and extensional processes were likely active during the recent time-scales.

Propagation characteristics of slow magnetoacoustic waves along coronal fan loops

Date: 2022-03-11
Speaker: Ms. Ananya Rawat
Venue: USO Seminar Hall

Abstract

The upper solar atmosphere i.e, corona (>1 MK) is much hotter than the surface of the Sun i.e, photosphere (<6000 K) which is unexpected according to second law of thermodynamics. To maintain such a high temperature there must be a constant supply of heat/energy to balance the various energy losses. Identification of such atmospheric heating mechanism is one of the major puzzle in solar and stellar physics. Several heating mechanisms have been proposed which are broadly classified into either magnetohydrodynamic (MHD) waves or magnetic reconnection based heating models. In this presentation, focus will be mainly on wave heating mechanism which are further divided into three steps such as generation, propagation, and damping of waves. In this talk, I will present analysis carried out by us to study the evolution and dynamics of propagating intensity disturbances characteristics of waves observed along the clean fan-loop system rooted in active region AR 12553.

Hands-on Astrophysics: Analysis of Presolar Stardust Grains to Decipher Stellar Nucleosynthesis

Date: 2022-03-10
Speaker: Dr. Reto Trappitsch, Brandeis University, Waltham, MA, USA.
Venue: Online

Abstract

The talk introduces how analyses of presolar stardust grains allow us to decipher the slow neutron-capture (s-) process in asymptotic giant branch stars. These measurements are therefore valuable to better understand how the material the Solar System formed from came together in the first place. The talk also introduces resonance ionization mass spectrometry (RIMS), a technique that allows us to analyze the trace element isotopic composition in such micrometer-sized samples. Finally, the background of stellar nucleosynthesis and existing measurements to constrain the s-process are discussed before concluding with an outlook to future RIMS measurements.

(1) Characteristics of Martian Ionopauses & (2) Impact of Mars 34 dust storm on the production rates of H2O+, HDO+ and D2O+: Implication of NOMAD/TGO observations

Date: 2022-03-04
Speaker: Prof. S. A. Haider
Venue: Online

Abstract

Recently 44th COSPAR scientific assembly will be held in Athens, Greece between 16-24 July 2022. In this meeting we will present two papers on the above topics. The preliminary results of both papers will be discussed in this seminar. In the first paper we have analysed plasma and magnetic field data obtained from 627 orbits of Mars Atmosphere and Volatile Evolution (MAVEN) that occurred during October 2014, April 2015, September 2017 and May 2018, when the spacecraft was crossing the magnetic pile-up boundary of Mars. A steep ionopause like boundary is observed in 24 profiles of 627 orbits, when MAVEN was passing from the magnetic pile-up region during the daytime ionosphere in presence of horizontal magnetic field of high strength, while their night side ionosphere did not show such boundary in presence of horizontal magnetic field of low strength. These profiles are unique, which have not been reported earlier. In the second paper we have estimated photoionization rates of H2O+, HDO+ and D2O+ in the Martian atmosphere during and before the Mars dust storm 34. The photolysis of H2O, HDO and D2O are also estimated during this dust storm event. In this calculation mixing ratios of H2O and HDO observed by Nadir and Occultation for Mars Discovery (NOMAD) instrument onboard ExoMars Trace Gas Orbiter have been used. The estimated photolysis and ion production rates of these molecules are larger by an order of magnitude in presence of dust storm than that estimated in the absence of dust storm.

Condensation and Radial Transport of Filamentary Enstatite Crystals from Interplanetary Dust

Date: 2022-03-03
Speaker: Prof. Ryan Ogliore, Washington University, St. Louis, U. S. A.
Venue: Online

Abstract

Filamentary enstatite crystals, formed by gas-solid condensation in the solar nebula, are found in chondritic porous interplanetary dust particles of probable cometary origin. We measured the oxygen isotopic composition of five filamentary enstatite grains from the giant cluster interplanetary dust particle U2-20 GCP. These grains sample both the 16O-rich solar (∆17O ≈ −30 per mil) and 16O-poor planetary (∆17O ≈ 0 per mil) isotope reservoirs. Our measurements provide evidence for very early vaporization of dust-poor and dust-rich regions of the solar nebula, followed by condensation and outward transport of crystalline dust to the comet-forming region very far from the Sun. Similar processes are likely responsible for the crystalline silicates observed in the outer regions of protoplanetary disks elsewhere in the Galaxy.

Mare-filled craters on the Moon: Classification, distribution and implications

Date: 2022-02-25
Speaker: Ms. Kimi Khungree Basumatary
Venue: Online

Abstract

Impact craters are the predominant features on the lunar surface. More than two million impact craters of varying diameters are reported on the lunar surface. Out of these two million craters, hundreds of lunar crater floors are filled with lava materials and are the direct evidence of post-modification. In this study, we systematically mapped such craters and analysed their diagnostic characteristics like infilling lava depth, presence/absence of peak, and posts infilling floor modifications (like floor collapse, fractures). We have identified 329 infilled craters with the diameter ranging from ~4 km up to ~270 km. We have included infilled craters with completely preserved enclosed rims to understand the infilling process through impact generated fractures and categorised the identified infilled craters into five classes (1a,1b, 2, 3 and 4) based on their crater morphology. These craters are distributed predominantly on the periphery of the mare, rims of mare filled impact basins, few on the highlands, and few within the mare/basins regions. The magma stalled beneath these craters intruded through the impact generated fractures and they overall revealed that the stalled magma depth varies across different region of the Moon. In this presentation, the identified mare filled craters classes based on their crater morphology, global distribution and implications will be discussed.

Atomic-Scale Structure and Non-Stoichiometry of Meteoritic Hibonite

Date: 2022-02-24
Speaker: Dr. Jangmi Han, University of Houston, U. S. A.
Venue: Online

Abstract

Hibonite (CaAl12O19) is a common refractory mineral in Ca-Al-rich inclusions (CAIs) in primitive meteorites and provides crucial insights into the conditions and processes that existed in the early solar nebula. Transmission electron microscope (TEM) studies have identified enigmatic planar defects in different occurrences of hibonite in the Allende meteorite. Atomic resolution high-angle annular dark-field (HAADF) imaging and energy dispersive X-ray (EDX) analyses were used to determine the nature and origin of these planar features. Our TEM analyses revealed that the modification of the stacking sequence in hibonite and its non-stoichiometry (i.e., Al and Mg excesses) likely played a major role in the formation and metastability of planar defects in hibonite. The formation history of planar defects in hibonite will be discussed to provide implications on the formation conditions for refractory first solids in the early and high-temperature evolution stage of our Solar System.

Analytical Investigation of Lunar Photoelectron Sheath

Date: 2022-02-18
Speaker: Trinesh Sana
Venue: Online

Abstract

Images of a horizontal glow on the Moon obtained by Surveyors 6 and 7 and seen by Apollo 17 astronauts were a sign of dusty plasma environments over the Moon, where sunlight is scattered by charged dust particles floating near the lunar surface. Being an airless planetary body, the Moon's surface directly interacts with solar radiation, solar wind, and terrestrial magnetospheric plasma. Due to the combined effect of dominant photoemission, solar wind, ambient plasma collection, the sunlit lunar surface acquire positive charges. The photoelectrons form a photoelectron sheath in the vicinity of the lunar surface. In this presentation, an understanding of the photoelectron sheath formation is discussed. The justified solar spectrum, solar wind flux, Fermi Dirac distribution of the photoelectrons have been taken in the formulation. Moon’s surface potential is determined by balancing the photoelectrons and solar wind plasma accretion currents. The sheath's potential and electric field profiles are determined by solving Poisson's equation with appropriate boundary conditions. The dependence of the surface potential and subsequent sheath profiles on various parameters will be discussed.

The Sun’s Twisted Magnetic Mysteries

Date: 2022-02-18
Speaker: Prof. Lucie Green

Abstract

This talk takes an in-depth look why the Sun produces the most energetic eruptions in the Solar System; events known as coronal mass ejections. Since their discovery in the early 1970s it has been realised that these eruptions occur due to changes in the Sun’s magnetic field. The eruptions appear to be related to a certain magnetic field configuration known as a flux rope. Understanding how and where flux ropes form has unravelled some of the mysteries around coronal mass ejections and understanding their magnetic structure has not only helped explain why these eruptions occur, but also what their space weather impact might be if they are ejected toward the Earth. This talk will explore further the role of the shapes that magnetic fields have in relation to eruptions and introduce a concept known as magnetic helicity. The most recent studies of magnetic helicity have shed new light on how eruptions might be forecast ahead of time. An exciting step forward that might be useful in the years to come for space weather forecasting.

Disordered Bose Hubbard model and percolation analysis

Date: 2022-02-17
Speaker: Hrushikesh Sable
Venue: Online --> https://bluejeans.com/174262927/0866

Abstract

The interplay between disorder and interactions in many-body quantum systems leads to novel quantum phases. The Bose-Hubbard model (BHM) is a prototypical model to describe the physics of ultracold atoms in optical lattices. In the context of the BHM, the introduction of disorder results in a Bose-glass (BG) phase, apart from the usual Mott Insulator and superfluid (SF) phases. In this talk, we shall discuss the equilibrium phase diagram and the properties of these quantum phases. In particular, we shall focus on the critical properties of the BG-SF phase transition. We shall demonstrate the methods of percolation theory to locate the phase boundary of the BG-SF transition.

Trace Element Isotopic Composition of Individual Presolar Silicon Carbide (SiC) Grains

Date: 2022-02-15
Speaker: Dr. Manish Sanghani
Venue: Online

Abstract

Presolar grains found in primitive meteorites condensed in the outflows of red giant or asymptotic giant branch (AGB) stars and in the stellar explosions before the formation of our solar system. These tiny dust grains survived isotopic homogenization in the early solar system, carrying nucleosynthetic signatures of their parent stars. Thus, multi-isotopic compositions of presolar grains help to better understand stellar nucleosynthesis, grain formation environments and galactic chemical evolution. Several meteorite samples show Cr- isotopic anomalies that are thought to have carried by presolar silicon carbide (SiC) grains. A vast majority of presolar SiC grains are mainstream grains condensed in ~1.5- 3 M⦿ AGB stars of near solar metallicity. Following their condensation in the inner shells of pre-supernova stars, Cr isotopes are inherited by AGB stars and reprocessed by slow-neutron capture (s) process. Cr-isotopic compositions of SiC grains from supernova can provide insights into the efficiency of mixing of ejecta layers in type-II supernovae explosion, while Cr- isotopic compositions of SiC grains from AGB stars could possibly tell us about some unusual stellar sources that may have contributed material to our solar system. The talk will briefly outline presolar SiC grains coming from various stellar sources and their multi-isotopic signatures. Background information on Fe-Ni and Cr isotopic compositions of presolar SiC grains will be presented. Cr-isotopic data reduction protocol will be summarised. A presolar SiC grain from AGB shows significantly higher anomaly in δ54Cr, that can not be explained simultaneously with the observed C and N isotopic compositions. A Stellar nucleosynthetic model (FRUITY- Full-Network Repository of Updated Isotopic Tables & Yields) will be discussed to explain the grain data. A finding that describes the first possible evidence of a population-II star as a stellar source of the SiC grain will be discussed.

Polarimetric SAR and its Application for Moon Surface Characterization

Date: 2022-02-11
Speaker: Dr. Nidhi Verma
Venue: Online

Abstract

The Synthetic Aperture Radar (SAR) is a powerful remote sensing tool providing the physical properties of the surface and subsurface. SAR is designed to create images from moving platforms and is capable of generating high-resolution natural surface images from airborne and spaceborne platforms. The advanced form of SAR is known as Polarimetric SAR. Polarimetric SAR, being a coherent device, has the capability to measure backscattering response from an object by recording both magnitude and phase at various polarization states; Linear (HH, HV, VV, VH), circular (RR, RL, LL, LR) and hybrid (RH, RV, LH, LV). Due to multidimensional information obtained from polarimetric SAR data, geometrical, physical and electrical characteristics of various objects can be obtained. Additionally, the multidimensional information makes it possible to determine different types of scattering (volume, surface, and double-bounce) and resolve uncertainty in scattering responses from various land covers. Polarimetric SAR uses a specific frequency (microwave frequencies) to penetrate beneath the earth surface. Polarimetric SAR technology is also being used for understanding Moon surface properties. As it is an active sensor, it can also be used to map Permanently Shadowed Regions (PSRs). I will present a case study on how polarimetric SAR observations are used to identify land cover and estimate surface parameters for earth-based applications. Implications of this to the MiniSAR data analysis (Chandrayaan-1). Furthermore, I will discuss the Dual Frequency SAR (DFSAR) onboard Chandrayaan-2, data reduction and framework development for exploring PSRs.

Volatiles on Mars - from meteorites to sample return

Date: 2022-02-10
Speaker: Dr Susanne P. Schwenzer, Associate Director Astrobiology OU School of Environment, Earth and Ecosystem Sciences, The Open University, Milton Keynes, U. K.
Venue: Online

Abstract

Volatiles on Mars come in two categories: those, which react or are reaction products, and those which are inert. The latter are the noble gases, which can record processes such as degassing or atmospheric loss without taking part in any reactions that might also happen. In the Martian meteorites they present a complex story that to this day has conundrums to offer – but maybe, just maybe we are getting an atmospheric sample with the first ever sample return mission that would allow us to solve a few of the open questions. Of the volatiles that react or are products of reaction, methane captures our imagination most, because it is enigmatic in its sporadic occurrence, and it could, maybe, if Earth is a good proxy, with all the hedging that language has to offer, be linked to life. But of course, we do not know that. What we know is that water has a long history on Mars, carved channels, and most importantly for this part of the story, altered minerals. This talk will present a personal journey of 25 years of research into the sources, pathways, reactions and sinks of noble gases, methane and water. Thus, the selection is biased, and very much guided by the speaker’s own excitement about topics such as the Kr/Xe ratio in the nakhlite Martian meteorites and the water rock reactions that form carbonates on Mars.

Science Outcome of Chang’E-5 Lunar Sample Return Mission

Date: 2022-02-04
Speaker: Dr. Amit Basu Sarbadhikari
Venue: Online

Abstract

Chang’E-5 (CE-5) was landed at 43.06◦N, 51.92◦W (north of Oceanus Procellarum) on the Moon on 1st December 2020. CE-5 brought back 1.731 kg regolith and fragmented rock lunar samples; the first samples returned to Earth in 44 years from the Moon. The landing site was selected on the basis of some prior science objectives: (i) away from the Apollo and Luna landing sites, (ii) location in the Procellarum KREEP Terrane (PKT), (iii) occurrence of one of the youngest lunar mare basalts, etc. In this talk, I'll discuss the key science questions to be answered by studying the returned CE-5 samples. I’ll show some recent findings after analyzing the returned samples. With the new data, as some questions are answered, new ones arise. Finally, I’ll discuss the implications of those findings to the lunar formation and evolution history.

Condensation and Radial Transport of Filamentary Enstatite Crystals from Interplanetary Dust

Date: 2022-02-03
Speaker: Prof. Ryan Ogliore, Washington University, St. Louis, U. S. A.
Venue: Online

Abstract

Energy releases and transfer in the solar atmosphere

Date: 2022-01-31
Speaker: Prof. Toshifumi Shimizu
Venue: Online

Abstract

This talk will focus on two topics: results from the first example of ALMA-Hinode-IRIS observations for solar microflares, and the introduction of the future Solar-C (EUVST) mission. Solar microflares are among the major energy input sources to form the active nature of the solar corona. The response of the lower atmosphere to events can provide new clues to investigate dynamical behaviors of microflares. Our Cycle 4 ALMA observation coordinated with Hinode and IRIS satellites allows us to investigate the response. The first half of the talk will discuss what we learned from this novel example of ALMA-Hinode-IRIS observations for solar microflares. The latter half of the talk will introduce our next solar physics mission Solar-C (EUVST), which has been approved for launch in the next 3-4 years. This mission will have a powerful EUV spectroscopic tool to investigate energy releases and energy transfer through the entire outer atmosphere.

Interplanetary Dust Particles: Study, Detection and Detector Calibration

Date: 2022-01-28
Speaker: Mr. Srirag Nambiar
Venue: Online

Abstract

Interplanetary Dust Particles (IDPs) or micrometeoroids found within the solar system are tiny dust grains, first deduced from Zodiacal light. Our solar system is immersed in a disk of such dust particles. Their study holds significance as their dynamic evolution has effect on planetary bodies, their composition can tell us about early solar system processes and study of their distribution can help explore exoplanets. Modelling of the dust distribution is also important for the safety of spacecraft, owing to damage by impact of high speed particles. Different observation techniques like thermal emission, radio observation and lunar micro-crater study have been employed to study these particles. In-situ dust detectors have been used in the past to get an idea about the distribution as well as particle properties. Here, the importance of IDP study and an Impact ionization detector under development will be discussed. Further, to calibrate such an instrument, a dust accelerator is required where a particle of known mass and velocity is accelerated and impacted on the detector. The two popular types of dust accelerators: Electrostatic Dust Accelerator and Two Stage Light Gas Gun are discussed. For initial optimization of the instrument a nanosecond pulse laser is used and such a facility has been setup at Institute for Plasma Research, Gandhinagar. The test carried out using pulse laser setup will also be briefly described.

Chondrule formation: A controversial issue among different models

Date: 2022-01-27
Speaker: Dr. Maria Eugenia Varela, ICATE-CONICET, San Juan, Argentina
Venue: Online

Abstract

Chondrites are the most primitive meteorites that preserve useful information about the time the Solar System formed, about 4.56 Ga ago. One of their major constituents are chondrules, μm to mm sized spherical objects which constitute up to 80% of the volume of the most primitive meteorites and are composed mainly of ferromagnesian silicates. The process/es involved in chondrule formation cover a wide range of mechanisms whose nature is still unknown. I will discuss the two principal models that are outlined concerning the origin of chondrules in the solar nebula. There is no real consensus regarding the nature of the initial liquid droplets from which chondrules are supposed to be formed, nor about the different processes that were active during and after chondrule formation. An alternative model: the Primary Liquid Condensation (PLC) model can explain the growth of single crystals through a process in which liquid condenses first and then nucleates a crystal of the species that is oversaturated in the vapor. This process refers to a vapor-liquid-solid growth process that take place in equilibrium with a chondritic reservoir. Finally, I will inform of the first glass inclusion hosted in spinel within a glass-rich chondrule from the unequilibrated ordinary chondrite Catalina 278 (LL3.4). A possible sample of the initial liquid trapped during spinel growth.

Grass-roots Innovations: Mining the Minds of Masses<img src='/prl-eng/images/red.gif'/>

Date: 2022-01-26
Speaker: Brigadier P Ganesham
Venue: ONLINE

Abstract

n the national eco-system of Innovation, main players are Public Innovations and Private innovations. Investment and guidance to Public Innovations is drawn from the Government. Over the years, these institutions have distanced themselves from the requirement of the general public and focused on the problems of the Industry and Government. Majority of the problems faced by the general public especially those in livelihood sector are not addressed by this category. Private Innovations are undertaken by corporate and other private investors with a view to promote their business and keep away from the problems of the masses. Monetary growth of business is possible with products of high cost, current technology, and for those customers who can afford to buy their products. Such innovations are driven by the need to improve upon their product based on perceived needs of the society. At times, they are found to aim at influencing the customer behavior and mostly they are not a result of customer needs. Thus, both the categories of Innovation eco system pay lip service to the masses of the nation resulting in their frustration, helplessness and anger. In such social scenario, a new category of Innovators emerges from these angry people and we may call them “Grass-roots Innovators”. Instead of actively voicing the problems – insurgency, they take a step forward to solve the problem- innovation. They are there everywhere, every house, every village and attempt to innovate continuously. Their innovation – solutions to the problems around them are generally affordable and appropriate. They follow the Gandhi an Mantra of “More from less for Many – a principle of MLM” which has been propounded by Dr R A Mashelkar. These grass-roots innovators attempt to find solutions to the local problems, using local resources and local technologies, thus making these creative solutions highly affordable. “Unmet Needs” of the villages are addressed by the creative villagers thereby reducing the pain of the people and enhancing the productivity. Dr Vergheese Kurien stated “India’s place in the Sun will come from the partnership between the wisdom of the rural people and the skill of its professionals.” Atma Nirbharata can be achieved when we focus our attention on the strengths of the villagers, leverage their creativity and traditional knowledge and add to what they have for attaining the national development goals. “Strengthen the Strengths should be our approach towards villages. Ultimate goal of any development plan should be happiness of masses. Can we achieve it? … ….

Instrumentation of Radio Occultation Experiment for future Mars Mission

Date: 2022-01-21
Speaker: Ms. Sonam Jitarwal
Venue: Online

Abstract

Radio occultation is one of the major applications of radio science in space missions and played a central role in determining the vertical structures of planetary atmospheres. The radio occultation experiment is carried out with an orbiter, where the spacecraft transmits radio waves to a tracking station on the Earth in case of transmitter mode (and otherwise, in case of a receiver mode). The radio waves sequentially pass through the neutral atmosphere and planetary ionosphere before re-emerging in reverse sequence. When the trajectory of the spacecraft takes it behind the planet seen from Earth, there is occultation by the planet’s atmosphere. During an occultation event, the refractive index of the gases in the ionosphere and atmosphere alter the characteristics of the propagating radio wave. Radio occultation experiment rely on the extreme frequency stability of both the on-board radio wave source and the recording system at ground. In this talk, I will present the design, implementation and testing results of Single Frequency Transmitter using multiplier chain. The Dual Frequency Transmitter can also be designed using Phase Locked Loop (PLL) based frequency synthesizer. Using double down conversion method, Single Frequency Heterodyne Receiver has been designed, tested and in-phase and quadrature-phase outputs gives an idea of received frequency with appropriate power level. We found Design Verification Model (DVM) of both the configurations working satisfactorily in laboratory.

Origin and evolution of nitrogen on planetary bodies in the inner solar system

Date: 2022-01-20
Speaker: Dr. Evelyn Füri, Centre de Recherches Pétrographiques et Géochimiques (CRPG, CNRS-UL), France
Venue: Online

Abstract

Knowledge of the origin of nitrogen on Earth is of particular importance to understanding the development of conditions favorable to the emergence of prebiotic molecules and the maintenance of life on rocky planets. However, the origin and timing of the accretion of nitrogen on Earth remains a subject of controversy. In this talk, I will present new data obtained by secondary ion mass spectrometry (SIMS) analyses of extraterrestrial melt inclusions. First, I will show that olivine-hosted melt inclusions in angrites and martian meteorites are key for constraining the source(s) and timing of nitrogen delivery to planetary bodies in the inner solar system. However, the effects of planetary formation processes (core formation, magma ocean crystallization and degassing) on the original elemental and isotopic composition of planetary mantles still need to be investigated.

How well can we link meteorites to asteroids

Date: 2022-01-13
Speaker: Prof. Thomas Burbine , Department of Astronomy, Mount Holyoke College, USA
Venue: Online

Abstract

Asteroids are the remaining planetesimals that helped form the terrestrial and Jovian planets. Asteroids, which are the parent bodies of almost all meteorites, are almost entirely observed remotely using Earth- and space-based telescopes with only a few bodies studied up close by spacecraft missions. The chemical and isotopic compositions of meteorites can be determined with high precision in laboratories on Earth; however, remote observations of asteroids give geochemical information. In this seminar asteroid-meteorite relationship will be discussed.

Boulder Fall Ejecta: Present Day Activity on Mars

Date: 2022-01-07
Speaker: Dr. S. Vijayan
Venue: Online

Abstract

Boulder falls are an archives of recent surface activity on planetary bodies, especially on Mars. However, determining how recently they fell on Mars remains elusive. High-resolution images of Mars have revealed numerous boulder falls on the surface. Multitemporal MRO-HiRISE image analysis reveals that new tracks are characterized by a herringbone-like ejecta pattern at each boulder bounce that is termed as boulder fall ejecta (BFE). First systematic survey of BFE revealed a few thousands of tracks formed recently and they are spread globally. BFE longevity analysis reveals that these tracks likely formed in the last few decades. From numerous examples we also observed slope streaks originating from BFE tracks, providing comprehensive evidence favouring a dry origin theory. Our results revealed that on Mars it takes ∼2 to 4 Mars years (4–8 Earth years) for BFE to disappear, whereas on Earth BFE are rarely preserved. This recent study revealed that the Cerberus Fossae region adjacent to NASA's InSight lander landing site hosts nearly 30% of BFE, suggesting it is a currently active region on Mars. Thus, BFE can be used to recognize very recent surface processes on planetary surfaces.

Nucleosynthetic heterogeneity in the early solar system: insights from Nd isotopes

Date: 2022-01-06
Speaker: Dr. Nikitha Susan Saji, Centre for Star and Planet Formation, Globe Institute, University of Copenhagen, Denmark
Venue: Online

Abstract

Isotopic variability from heterogeneous distribution of presolar dust in the solar protoplanetary disk is now well-established for a number of elements. Yet, significant uncertainty exists regarding the inventory of presolar dust populations that were initially present in the protosolar molecular cloud and their eventual aggregation into planets and planetesimals. In this talk, I will review what high precision Nd isotope measurements of meteorites and their components tell us about the diversity of nucleosynthetic components that contributed material to the nascent solar system and how they resulted in an apparent bifurcation of solar system materials into carbonaceous and non-carbonaceous suites.

Precision Prediction of Higgs cross section and New Physics signals in B-decays

Date: 2022-01-06
Speaker: Dr. Shireen Gangal
Venue: Online --> https://bluejeans.com/386832560/8794

Abstract

In the first part of my talk, I will discuss precision predictions of Higgs production cross section via gluon fusion, with a veto imposed on additional jets using rapidity-dependent jet vetoes. These jet veto observables provide a tight veto at central rapidity, gradually transitioning to a loose veto at forward rapidities. I will present predictions for the Higgs+0-jet cross section using these rapidity-dependent jet vetoes at NNLL' + NNLO accuracy within the framework of Soft Collinear Effective Theory. In the second part, I will discuss the intriguing hints of lepton flavour universality violation that have accumulated in B-meson decays. In a recent re-analysis of 2018 Belle data, it was found that the lepton forward-backward asymmetry of B→ D* μν vs B→ D* eν decays is in tension with the SM prediction. I will present results of a global fit to b → c l ν data which show that a new physics scenario with scalar and tensor operators can significantly reduce this tension.

2021

Study of Dust particle evolution in Solar system using Mercury code package

Date: 2021-12-31
Speaker: Ms. Rashmi
Venue: Online

Abstract

The asteroid belt is one of the major sources of dust particles in the solar system. Other sources of dust particles are the Kuiper belt and cometary sublimation. These dust particles experience different types of forces like gravitational forces, pressure forces (Poynting Robertson Drag, Radiation Pressure), Lorentz forces, etc. Under the effect of these forces, these dust particles evolve over years and deviate from their initial orbits. To understand how different forces are affecting these dust particles geometrically over the years, N-body integration needs to be done. Here, the Mercury code is used to integrate these forces. In this seminar, I will discuss how these forces affect the dust particles and the integration technique. Later, I will discuss some of the initial results of the evolution of the dust particle's orbit from their initial orbit.

Chondrites and the early solar system

Date: 2021-12-30
Speaker: Dr. Yogita Kadlag, NCCR PlanetS advanced Post-Doctoral fellow, Universität Bern, Switzerland
Venue: Google meet

Abstract

Precursors of all solar system objects such as meteoroids, asteroids, comets, proto-planets, and planetary satellites were formed through physical and chemical processing (e.g. condensation-evaporation, variable heating, mixing, etc.) of nebular dust and gas of about 0.1% solar mass. To understand the role of initial chemical and isotopic heterogeneity and subsequent physicochemical processing of dust, gas and planetary precursors in the solar nebula, chemical and isotopic variations in the components of undifferentiated meteorites such as calcium-aluminum-rich inclusions, chondrules, matrix and Fe-Ni metal can be used as tracers. Here, I discuss examples of chondrules and separated components from unequilibrated chondrites to explore the origin of isotopic heterogeneities and processing of mm to cm scale objects within the first few million years of the solar system evolution.

Electric Field Measurement in Planetary Atmosphere: Techniques and Instrument Development

Date: 2021-12-24
Speaker: Mr. Sanjeev Kumar Mishra
Venue: Online

Abstract

The electric-field and plasma densities are essential quantities to be measured in order to understand the dynamics of plasma processes. Electric field measurement using double-probe technique is simple yet effective technique based on Langmuir Probe technique. In this talk, I will discuss the heritage of electric field measurement for earth observations as well as those in other planetary atmosphere and the technique of measurement using spherical double-probes. At PRL, we are developing an instrument for measurement of these electric fields. Some of the developmental aspects will also be presented.

First Formed Solids: Records of the Earliest Times of the Solar System

Date: 2021-12-23
Speaker: Dr. Prajkta Mane , Visiting Scientist, Lunar and Planetary Institute (USRA), Astromaterials Research and Exploration Science Division, NASA Johnson Space Center, Houston TX 77058
Venue: Google meet

Abstract

Meteorites and their components can be used to unravel the history of the early Solar System. Carbonaceous chondrites are meteorites that originated from undifferentiated parent bodies that formed within a few million years of the beginning of the Solar System. These meteorites contain calcium-aluminum-rich inclusions (CAIs), which are the oldest dated solids forming in our Solar System at ~4.567 billion years old and thus preserve a record of the earliest stage of Solar System formation. The radiometric dating of these CAIs and other meteoritic components provides important time constraints on the events that occurred in the early Solar System, whereas textures and microstructures in these CAIs preserve the evidence of disk processes in them. In this talk, I will discuss the results of a coordinated multi-technique approach to analyzing CAIs and their components to reveal the timescales and conditions of their formation.

Quest for New Physics with the ratio of CKM elements

Date: 2021-12-23
Speaker: Dayanand Mishra
Venue: Online --> https://bluejeans.com/231422431/5680

Abstract

The CKM elements $|V_{ub}|$ and $|V_{cb}|$ show a discrepancy between the exclusive and inclusive determinations. These determinations are however masked with hadronic and other uncertainties, and thus can’t be unambiguously taken as implying new physics. In this talk, we consider a new observable: the ratio of these two CKM elements, $R_{V} ≡ \frac{|V_{ub}|}{|V_{cb}|}$, which is found to receive negligible corrections due to hadronic as well as QED effects. It is observed that the $R_{V}$ as constructed from exclusive determinations of $|V_{ub}|$ and $|V_{cb}|$ agrees quite well with that constructed from the inclusive determinations of these CKM elements. Hence, we show that $R_{V}$ is a cleaner observable, and can serve as an excellent tool for the test of the Standard Model.

Sustainable groundwater resource use in India-Achievable or a mirage?

Date: 2021-12-22
Speaker: Prof. Dipankar Saha
Venue: ONLINE

Abstract

Groundwater is the lifeline for food and drinking security in India. With the initiation of the Green Revolution in late 1960s, groundwater utilisation has occupied the forefront of water policies and practices in India. Today, India is the largest extractor of groundwater in the world, even exceeding the China and USA together. It contributes about 10% of India’s GDP and the irrigation economy connected to this resource is valued as 75 -80 billion US $/year. Volumetrically it accounts for 38% of total utilisable water resources of our country, but caters about 65% of the irrigation need, 85% of rural drinking water supply and more than 50% of urban water demand. The Industries also depend to a great extent on aquifers. Monsoon is the main source of groundwater resource recharge and India is blessed with adequate rainfall and well defined monsoon season. However, unplanned and unsustainable extraction is witnessed in many parts of India, particularly in the western, north-western and southern peninsular regions, resulting in drying up of wells, dwindling yields, saline water ingress in coastal aquifers and chemical quality deterioration. About 1/5th of the geographical area of the country is marked by annual groundwater extraction much exceeding the recharge. The Indus and the adjoining Gangetic aquifers in the north-western India is demarcated as one of the three most severely groundwater stressed regions in the World. The latest census tells about 22 million wells are working in India for the irrigation sector only. Sustainability in groundwater extraction is achieved when we extract equal to or less than the recharge in an annual cycle in a long term scenario. Considering the raging overexploitation, will it be possible to achieve sustainability? There are many issues to be considered and measures to be taken. Since agriculture consume >90% of total extraction, there is an urgent need to enhance irrigation efficiency and crop diversification, which is an uphill task. Groundwater is a distributed resource and developed by millions of wells, it is thus necessary to involve the community and the stakeholders its development and management. How to break groundwater-energy nexus and what are the innovative ways to regulate groundwater extraction for irrigation? Since long we thought of only supply-side intervention for bring sustainability, now the time has come to embrace and promote the demand-side interventions also. There is a strong need for strengthening groundwater institutes, scientific research and knowledge base.

Development of a drilling system for subsurface sampling on the Moon under PRST project

Date: 2021-12-17
Speaker: Mr. Abhishek J. Verma
Venue: Online

Abstract

Rover/lander based in-situ sample analysis missions and sample return missions are the next logical steps with respect to the Indian space exploration endeavours in the upcoming few decades to further our understanding of the formation and evolution of our solar system. The key to the success of these futuristic endeavours largely depends upon our ability to robotically acquire desired rock and soil samples from planetary surfaces and sub-surfaces under a gamut of challenging environments, such as low gravity (Moon, comet, and asteroids), low pressure (6 millibar for Mars to UHV on Moon), and temperature as low as ~100 K in the lunar PSRs. In this prospective ISRO project entitled “Planetary Rock Sampling Technology”, which is to be jointly undertaken by PRL and VSSC, we aim to develop an automated core drilling system for acquiring 1.5-2 m deep stratified sub-surface samples from Moon, Mars, and other small solar bodies for future sample return missions. Considering the complexities involved and the task of development from a base level, we plan to accomplish the goal of the project in a phased manner. In this talk, I will provide an account of the project definition, international scenario, requirements for design and development, criticalities involved, selected approach covering the baseline design of the system and other important techno-managerial aspects of the project.

Isotopic constraints on the conditions of chondrule formation in carbonaceous chondrites

Date: 2021-12-16
Speaker: Prof. Yves Marrocchi, Research Director at CNRS, Deputy Director of the CRPG, France
Venue: Google meet

Abstract

In this talk, I will review the recent measurements carried out on chondrules of carbonaceous chondrites for different isotopic systems (O, Si, Cr, Ti). I will use these data to discuss the different models of chondrule formation in the framework of both planetary and nebular scenarios.

Field Emission-Electron Probe Micro Analyser (FE-EPMA): New tool for in-situ, non-destructive analysis of Planetary materials

Date: 2021-12-10
Speaker: Ms. Garima Arora
Venue: Online

Abstract

Electron Probe Micro Analyser (EPMA) is a precise, in-situ, non-destructive, quantitative elemental analysis tool for micron-sized (or even sub-micron sized) volumes at the surface of materials, with sensitivity at the level of ppm. It utilizes the various radiations excited by an electron beam incident on a flat surface of the polished sample. EPMA instruments are equipped with several built-in microscopy and spectrometer tools that allow for simultaneous X-ray (EDS and WDS depending upon the requirement) analyses, Secondary Electron Microscopy (SEM) and Back Scattered Electron (BSE) imaging, plus sophisticated visible light optics. In this talk, I will be discussing about different techniques and also about the advantage of using FE-EPMA as compared to conventional Tungsten EPMA (existing, older one in PRL). Additionally, I will also show the preliminary results on the performance of the instrument which include the calibration and some initial results using the reference sample analysis.

Initiation and Driving of Solar Eruptions

Date: 2021-12-10
Speaker: Dr. Bernhard Kliem
Venue: Online

Abstract

An overview will be given of our current knowledge how solar eruptions are initiated and driven, with an emphasis on the eruptive filament/CME component. The Ideal MHD (aka Flux Rope or Loss of Equilibrium) model will be compared with the Reconnecion (aka Arcade) models (primarily the Tether Cutting and Breakout models). This is closely related to the source-region core structure, whose formation will be briefly discussed. Next, I will consider what could lead to confined eruptions instead of CMEs, which is related to the properties of the overlying flux. Partial eruptions will be briefly touched. Finally, some aspects of the numerical modeling of flux rope eruptions will be considered. Here I will show some examples of event modeling that use the active-region model by Titov & Demoulin and examples that use a data-constrained source-region model.

The Origins of Organic Matter and Amorphous Silicates in Meteorites – Clues from Nanoscale Investigations

Date: 2021-12-09
Speaker: Prof. Christian Vollmer, Institut für Mineralogie, WWU Münster, Germany
Venue: Google meet

Abstract

Pristine carbonaceous chondrites provide important samples of the very early solar nebula. These complex rocks recorded snapshots of events 4.56 Ga years ago that can be disentangled by advanced analytical techniques on Earth. One of the most challenging components to analyze within such chondrites is the so-called “matrix”, a fine-grained mixture of presolar dust, amorphous and crystalline silicates, organic matter, sulfides, and metal, in which larger constituents such as chondrules or refractory inclusions are embedded. Organic matter (OM) and amorphous silicates within chondrite matrix are specifically important, because they record crucial condensation and synthesis processes in the solar nebula and meteorite parent bodies, but are also prone to alteration and destruction. In this talk, I want to summarize recent work by high-spatial resolution analysis techniques (TEM, UltraSTEM, NanoSIMS) on amorphous silicates and organic matter in a variety of pristine carbonaceous chondrites. We analyzed the functional chemistry signatures of these unique materials by electron energy loss spectroscopy (EELS) and synchrotron X-ray spectroscopy methods (STXM) to disentangle complex formation pathways. Organic matter records very early biomolecule reaction pathways, whereas the chemical composition and Fe oxidation state of amorphous silicates within matrix regions can be analyzed to understand early solar nebula condensation and alteration processes.

SHARAD study of the Martian graben system

Date: 2021-12-03
Speaker: Rajiv R Bharti
Venue: Online

Abstract

Grabens are very old and common martian surface features; however, the formation process is still debatable. Two hypotheses emerge from the earlier studies. One hypothesis suggests that volcanic rifting may be responsible for the formation of these grabens, while another hypothesis suggests that this process was initiated due to dike intrusion in the subsurface layer. We investigate the subsurface of the graben and nearby area of two major Tharsis grabens systems, Mangala Fossa and Labeatis Fossae, to get a more in-depth understanding, using the Shallow Radar (SHARAD) instrument on Mars Reconnaissance Orbiter. I will discuss the previously unreported subsurface reflectors at these locations and try to understand the significance of these reflectors in the formation process of the graben system.

Sulfur isotope anomalies in Acfer 094 inherited from the Irradiation of the Protosolar Molecular Cloud by Massive Nearby Stars.

Date: 2021-11-30
Speaker: Dr. Lionel Vacher, Washington University St. Louis, USA
Venue: Online

Abstract

Spectral line (121.6 nm) and larger or smaller wavelengths produce MI anomalies that define distinct ∆36S/∆33S ratios. Young stars have strong emission at Lyman-alpha, while massive O and B stars dominate the interstellar UV flux. Thus, the photodissociation of H2S can serve to differentiate between massive stars and young T-Tauri stars as the astronomical source of isotope-selective photodissociation. Analysis of paired oxygen and sulfur isotope systematics in cosmic symplectite (COS)−a nm-scale intergrowth of 16O-poor magnetite and pentlandite−in the primitive carbonaceous chondrite Acfer 094 can provide unique insights into photochemical processing of Solar System materials. Acfer 094 shows similarities to cometary material and, therefore, may have formed in the outer Solar System where it could have incorporated 16O-poor water ice that also contained H2S ice like that detected in comets. Sulfur in COS may provide insights into the astrophysical environment for the Solar System formation. In this talk, I'll report the oxygen and sulfur isotopic composition of COS and determine the likely astrophysical UV source responsible for photochemical processing of Solar System solids.

Geology of Australe region on the Moon

Date: 2021-11-26
Speaker: Ms. Neha Panwar
Venue: Online

Abstract

Understanding the magmatic processes on the Moon and their possible association with impact cratering processes is fundamental to decipher its thermal and geological history. Magmatism on the near side can be seen in the form of the mare deposits; however, on the far- side the basalts are present in isolated pockets only and the extent and nature of magmatism is not clearly known. Mare Australe, a mare that lies partly on the near-side and partly on the far-side provides a unique location to not only understand the mare filling processes on the Moon but also how impact processes affected the surface during the pre-Nectarian time. Unlike most mare deposits on the moon, the Australe mare deposits are present in small pockets spread throughout the suggested basin. Moreover, the extent of Australe basin and its association with the existing volcanic deposits is not fully established. The present study aims to define the extent of the Australe Basin by providing geological evidence for the same. It also attempts to decipher the nature and composition of magmatism in the Australe Basin and surrounding areas to understand further the relationship between the magmatic and impact cratering processes on the Moon.

Serpentinization of iron-rich olivine and its potential for abiotic methane synthesis in planetary bodies

Date: 2021-11-25
Speaker: Dr. Alik Sundar Majumdar, Department of Applied Geology Indian Institute of Technology (Indian School of Mines) Dhanbad Jharkhand, India
Venue: https://meet.google.com/fns-cpjv-snn

Abstract

Serpentinization of olivine-rich ultramafic rocks are increasingly recognized to have been widespread in the solar system throughout its history. This process has gained particular attention among planetary scientists because it generates molecular hydrogen (H2) and methane (CH4), compounds that can supply metabolic energy to biological communities and contribute to greenhouse warming of planetary atmospheres. Following this, the talk will demonstrate a series of natural (meteorites) and experimental observations as well as thermodynamic models to show the pattern of secondary mineral formation and H2 generation during serpentinization of olivine as a function of Fe content and temperature. It will also be shown that serpentinization of Fe-rich olivine can generate substantially greater amounts of H2 per mole than is observed for serpentinization of Mg-rich olivine, depending on the magnitude of Fe (III) partitioning into serpentine phase. Thus, serpentinization on planetary bodies may have a greater potential to supply H2 vis-à-vis CH4 to support biological communities and enhance the atmospheric greenhouse warming than analogous processes on Earth.

Constraining thermal processing of dust grains in space and on the surface of airless bodies through in-situ laboratory experiments

Date: 2021-11-18
Speaker: Dr. Pierre Haenecour, Lunar and Planetary Laboratory, The University of Arizona, Tucson, USA
Venue: Online

Abstract

Fine-grained material in chondritic meteorites typically consists of a mixture of crystalline and amorphous silicates, oxides, sulfides, Fe-Ni metal grains, and carbonaceous matter that accreted together from the solar protoplanetary disk. Some of these ‘primary’ phases were affected by secondary processing, including both heating and aqueous alteration, on their host asteroid. The response of these materials to secondary alteration is important for understanding active processes on the surfaces and within the chondrite-parent asteroids. Thermal metamorphism, in particular, could have played an important role in processes such as melting, volatile loss, elemental diffusion between grains, and driving hydrothermal processing. In my talk, I will discuss how we are using in-situ heating experiments inside electron microscopes to better understand the effect(s) of heating on the composition and microstructure of fine-grained materials.

Dr. Arvind Bhatnagar Memorial Lecture 01, The Sun's Magnetic Field and Global Climate Change

Date: 2021-11-17
Speaker: Prof. Sami K. Solanki
Venue: Online

Abstract

The Sun is a restless star. It shows a wide variety of transient or active phenomena, such as dark sunspots, the continuously changing hot corona, energetic flares and immense coronal mass ejections, together with the associated output of energetic radiation and particles. The single quantity that is responsible for the continuing unrest of the Sun is its tangled and dynamic magnetic field. It produces these and many more fascinating phenomena, including variations in the Sun's radiative output or irradiance, which has been invoked as a source of solar influence on the Earth's climate. After an introduction to the Sun and its magnetic field, a short history of solar activity will be given and how that relates to the changing climate on Earth. Finally, the question is considered to which extent the Sun is responsible for the global warming seen in the last century.

Noble gas mass spectrometry (NGMS) and neon isotopes in ordinary chondrites

Date: 2021-11-12
Speaker: Mr. Avadh Kumar
Venue: Online

Abstract

NGMS is a multi-collector mass spectrometer for measurement of isotopes noble gases (He, Ne, Ar, Kr and Xe) and nitrogen. This requires extraction of gases from the solid samples, under the UHV conditions. There are different ways to extract gas: (resistance furnace, Laser Microprobe, Vacuum crusher and combustion system). Depending upon the scientific requirement, suitable method is applied to extract the gases. In this talk, I will discuss the gas extraction method, operational conditions of NGMS and one application using neon isotopes. The isotopes of neon are used widely to understand trapped components, cosmic ray exposure age and many other scientific aspects. Although there are more than 50,000 meteorites in worldwide collection, only few meteorites are studied for neon isotopes, due to mass limitations. In this work, I have compiled the neon isotopic data in ~800 ordinary chondrites from published literature, with the aim to identify number of parent bodies for the suit of ordinary chondrites, and their regolith history. The bulk dataset is also used to identify the major trapped component, knowledge of which is essential for the planet formation.

Probing Solar and Stellar Physics by Helio- and Asteroseismology

Date: 2021-11-12
Speaker: Prof. Dr. Markus Roth
Venue: Online

Abstract

The Sun and the stars are subject to sound waves that probe their interiors. Observations of these solar and stellar oscillations have emerged as a powerful tool to gain information on the processes inside the Sun and the stars. Through helio- and asteroseismology detailed inferences of the stellar internal structure and of the physical processes inside stars can be obtained. In particular, helioseismology allows studying large-scale flows, sunspots and other magnetic active areas on the Sun. The latter have an important impact on our technological society through potentially harmful solar eruptions. However, a complete understanding of the Sun, and in particular of its magnetism, can only be obtained by understanding the internal structure and properties of the stars in general. Asteroseismology offers the possibilities to address this problem.

Heterogeneous accretion of volatiles to Earth's mantle reservoirs

Date: 2021-11-12
Speaker: Dr. Rita Parai, Washington University, U. S. A.
Venue: Online

Abstract

Earth’s interior retains volatiles (e.g., nitrogen, carbon, hydrogen and the noble gases) acquired during accretion. Solar, chondritic and cometary noble gases may all have contributed to terrestrial volatile reservoirs. This study shows that helium (He), neon (Ne) and xenon (Xe) isotopes of the upper mantle and the plume mantle source can only be explained if the latter reservoir had a low initial Xe abundance. A record of limited accretion of volatile-rich chondrites into the deep mantle compared to the upper mantle thus survives in the He-Ne-Xe signatures of mantle rocks today. Energetic impacts during accretion did not homogenize the growing planet, and early-formed 129Xe and 182W mantle heterogeneities may have survived through ~4.5 Gyr of mantle mixing due to a viscosity contrast originating from differential accreted water contents in the plume and upper mantle reservoirs.

Mesoscale meteorology of the Martian atmosphere

Date: 2021-10-29
Speaker: Dr. Shefali Uttam
Venue: Online

Abstract

The Planetary Boundary Layer (PBL) is the lowest part of the atmosphere that is directly influenced by the surface. It responds to the surface forcing in a timescale of an hour or less, therefore the vertical mixing is strong. The local topography and solar radiation play a key role in guiding the local and regional scale meteorology of the atmosphere, which cannot be computed by a global scale model. Hence, we use a mesoscale model (LMD-Mars Mesoscale Model) to study about the local and regional scale meteorology of Mars. The mesoscale models solve for the equations of motion for the atmospheric fluid which are integrated on a grid, with a resolution of tens of meters to a few kilometers. This helps in modeling the dynamics of boundary layer, so as to understand about the generation of turbulence in the atmosphere. In this talk I will discuss about the mesoscale meteorology of the Martian atmosphere and show some preliminary results from my analysis.

Energy-weighted Message-Passing Networks

Date: 2021-10-28
Speaker: Ng. Vishal Singh
Venue: Online --> https://bluejeans.com/626648208/1962

Abstract

Hadronic signals of new-physics origin at the Large Hadron Collider can remain hidden within the copiously produced hadronic jets. Unveiling such signatures requires highly performant deep-learning algorithms. In this talk, I will discuss the construction of a class of Graph Neural Networks (GNN) in the message-passing formalism that makes the network output infra-red and collinear (IRC) safe, an important criterion satisfied within perturbative QCD calculations. Including IRC safety of the network output as a requirement in the construction of the GNN improves its explainability and robustness against theoretical uncertainties in the data. We generalise Energy Flow Networks (EFN), an IRC safe deep-learning algorithm on a point cloud, defining energy weighted local and global readouts on GNNs. Applying the simplest of such networks to identify top quarks, W bosons and quark/gluon jets, we find that it outperforms state-of-the-art EFNs.

Entering an Unseen World: Biology vs. Science – Who sees further?

Date: 2021-10-28
Speaker: Dr. Frank Gyngard, Harvard, USA
Venue: Online

Abstract

Over the last many decades, there has been an undeniable advance in our ability to see into materials at the micro and nano scale, that not even the highest-powered optical microscope could reveal. >From meteorites to cells, this revolution has revealed to us the substructures and wonders of natural phenomena. This talk will focus on the parallels of applying NanoSIMS techniques to both biology and cosmochemistry/presolar grains. It will also give some general advice gleaned from the world of biology, in terms of grants, publications, and general outlook for future NanoSIMS studies. And for fun, you will also see the Chicago car tow lot!

Dust Clouds in Solar System and Latest Results by Juno

Date: 2021-10-22
Speaker: Dr. Jayesh P. Pabari
Venue: Online

Abstract

Interplanetary Dust Particles (IDPs) exist everywhere in our solar system. The IDP is expected to be originated from Asteroid belt and bigger particles travel inward, towards Sun. Occasionally, comets also contribute dust in the inner solar system. Existing dust clouds create zodiacal light after interaction with the sunlight. Recently, Juno spacecraft has provided observations of dust during its cruise phase from Earth to Jupiter. The speaker will convey dust clouds and sources of IDP in the initial part of the talk. In the later part, he will cover the latest results from Juno.

The European Solar Telescope: A telescope for the XXI century

Date: 2021-10-22
Speaker: Prof. Manolo Collados
Venue: Online

Abstract

With first light expected at the end of the present decade, the European Solar Telescope (EST) represents the most important technological joint effort made by the European ground-based Solar Physics community. EST will improve considerably the present observational capabilities thanks to its 4-metre diameter. Its optical design is especially designed to study magnetic phenomena taking place in the solar atmosphere, optimising two crucial aspects. On the one hand, its polarimetrically-compensated design is conceived to cancel out the instrumental polarisation induced by the individual elements of the telescope optical train. This property is crucial to detect very small, both spatial and temporal, fluctuations of the magnetic field. Secondly, its design includes a powerful multi-conjugate adaptive optics system (MCAO) to optimally correct the wave-front distortions introduced by the Earth's atmosphere. With this MCAO system, EST is intended to measure the Sun at diffraction limit, with a spatial resolution of 20-30 km and a cadence of few seconds. The design is complemented with the most advanced suite of instruments that will operate simultaneously, to extract the maximum information about the dynamics, thermodynamics and magnetism of the solar plasma at different layers. In this talk, the status of the project will be presented, putting emphasis on the most recent technical developments, the instrumentation and on the scientific goals that will be addressable with this facility.

Nascent Sun & repetitive Super flares

Date: 2021-10-21
Speaker: Dr. Ritesh Mishra, Application Engineer, Cameca, India
Venue: Online

Abstract

The chronology of the early Solar system events during the first few millions years are presently constrained at a few 100 ka which is a few orders of magnitude larger than the typical time scale of a few 100-1000 years of evaporation, condensation, cooling, solar flaring events (FUor) etc.. Evidence of such a high resolution temporal record of a superflare from the young Sun during its birth inferred from fossil records of 7Be, 10Be will be presented in the talk.

The Inverse Evershed Flow - Data, Analysis Methods, Results, Physics, Model

Date: 2021-10-17
Speaker: Dr. Christian Beck, National Solar Observatory (NSO), USA
Venue: Online

Abstract

The (inverse) Evershed Flow ((I)EF) was discovered by J. Evershed in 1908 in spectroscopic observations taken at the Kodaikanal Observatory. He found that all photospheric spectral lines in the penumbrae of sunspots showed a persistent pattern of Doppler shifts. On the limb side of the sunspot, the spectral lines were displaced to the blue and on the center side to the red. This "regular" EF can be well explained by a radial outflow away from the umbra at photospheric heights inside the penumbra of sunspots. In all chromospheric lines, the exact opposite pattern was observed with an inflow towards the sunspot in the superpenumbra. The EF has been studied extensively ever since, but corresponding studies of the IEF are rare. In this talk I will present the recent results of our group of a series of studies on the properties of the IEF. We applied a variety of analysis techniques such as bi-sector analysis, thermal or magnetic inversions, magnetic field extrapolations, and a center-to-limb variation study with simplified modeling to high-resolution observations of the IEF. Our results demonstrate that the IEF is a field-aligned flow along magnetic field lines that connect the outer penumbra with the outer end of the moat cell in the form of arched loops. The positive field strength difference and the negative temperature difference between the inner and outer end point induce a flow towards the sunspot through the pressure balance and the siphon flow principle. We find to first order a quantitative agreement of the observed flow speeds and those predicted from the pressure balance equation.

Minor and trace element concentrations in adjacent kamacite and taenite in the Krymka chondrite

Date: 2021-10-14
Speaker: Dr. Smail Mostefaoui, Paris, France
Venue: Online

Abstract

We report NanoSIMS in situ siderophile minor and trace element abundances in individual Fe-Ni metal grains in the unequilibrated chondrite Krymka (LL3.2). Associated kamacite and taenite of 10 metal grains in four chondrules and one matrix metal were analyzed for elemental concentrations of Fe, Ni, Co, Cu, Rh, Ir, and Pt. The results show large elemental variations among the metal grains. However, complementary and correlative variations exist between adjacent kamacite-taenite. This is consistent with the unequilibrated character of the chondrite and corroborates an attainment of chemical equilibrium between the metal phases. The calculated equilibrium temperature is 446 ± 9 °C. This is concordant with the range given in literature for the Krymka post-accretion thermal metamorphism. Based on Ni diffusivity in taenite, a slow cooling rate is estimated of the Krymka parent body that does not exceed ~1K Myr-1, which is consistent with cooling rates inferred by other workers for unequilibrated ordinary chondrites. Elemental ionic radii might have played a role in controlling elemental partitioning between kamacite and taenite. The bulk compositions of the Krymka metal grains have nonsolar (mostly subsolar) element/Ni ratios suggesting the Fe-Ni grains could have formed from distinct precursors of nonsolar compositions or had their compositions modified subsequent to chondrule formation events.

VERDI AIDA ASIC based readout for Silicon Drift Detector (SDD) and digital temperature control using FPGA for SDD

Date: 2021-10-08
Speaker: Mr. Nishant Singh
Venue: Online

Abstract

Miniaturization of the overall instrument design and resource requirement is very critical for any space-based instrument and an Application Specific Integrated Circuit (ASIC) helps to achieve the same. I will be presenting the design and characterization of VERDI AIDA, an application specific integrated circuit (ASIC) board designed to operate with Silicon drift detector. We plan to used ASIC based readout to work in range of 0.5 keV to 15 keV and achieve a resolution of 140 eV @ 5.9 keV or better. AIDA is a 100mm x 70mm x 15mm multi-channel readout electronics board with 8 independent analog inputs from external charge preamplifier. I will present the performance of ASIC with different inputs given to the VERDI and discuss the development of inhouse control for the ASIC. Silicon Drift Detectors (SDD) are often used in the planetary missions as solid-state X-ray detectors in different types of spectrometer applications. They have low detector capacitance, low leakage current and reduced noise due to integrated FETs, hence providing very good energy resolution at high count rates. One of the main parameters that dictates the performance of the SDD spectrometer is temperature of the detector chip and hence it is desirable to maintain the detector temperature to a particular value during the measurements. In our design we have chosen a look-up table-based implementation on Field Programmable Gate Array (FPGA) to control the temperature of the SDD. I will present the working and the performance of the controller. With this design, we have been able to measure and control the detector chip temperature with an accuracy of ±0.5o C in range of -50o C to 30o C and achieved a resolution of 173 eV @5.9 KeV.

Isotopic and elemental studies of presolar graphite grains and what they tell us about their parent stars

Date: 2021-10-06
Speaker: Dr. Manavi Jhadav, University of Louisiana, USA
Venue: Online

Abstract

The laboratory study of stardust or presolar grains is an important sub-field of astrophysics. It combines sophisticated chemical, structural, and isotopic laboratory measurements, on micron-sub-micron presolar particles, with the theoretical ideas of nucleosynthesis and stellar evolution that exist to understand astrophysical observations. Isotopic data for these grains reveal more precise information about their parent stars than do spectroscopic observations of circumstellar dust. The goal of laboratory measurements is to provide clues on the stellar environments in which the grains formed and on their subsequent histories. Additionally, investigations into the preservation of these grains in different meteorites provide information about early solar system conditions and chronology. These goals can be achieved by coordinated, multi-technique investigations of presolar grains in the laboratory. This talk will focus on results from coordinated, multi-technique measurements of presolar graphite grains and what they tell us about the stars that contributed presolar materials to our nascent Solar System.

The overproduction of truth: from passion to market

Date: 2021-09-30
Speaker: Dr. Navinder Singh
Venue: Online --> https://bluejeans.com/682044853/7622

Abstract

In the 19th and first half of the 20th century, the number of scientific discoveries scales as linear with the number of scientific publications. But from the second half of the 20th century, the number of publications far exceeds the number of impactful discoveries. Does an exponentially growing number of publications indicate an element of pathological research? Pressure to publish a large number of papers has led to the phenomena of overproduction, unnecessary fragmentation, overselling, and deliberate obfuscation of scientific results so as to sell and oversell. This also has led to the phenomenon of predatory journals (pay and publish), and clever plagiarism. This is harming the healthy scientific culture of passion driven research. This is an urgent problem which needs attention of the whole of the scientific community. Ways to mitigate these grave problems are discussed.

Electronic transport due to magnetic scattering mechanisms: the Memory Function Approach

Date: 2021-09-23
Speaker: Komal Kumari
Venue: Online --> https://bluejeans.com/116525241/1376

Abstract

I present the theoretical analysis of electronic transport in magnetic materials. In these materials the electrical resistivity originates from electron magnetic spin fluctuation scattering (alongwith electron-phonon scattering). I use the Kondo-lattice Hamiltonian to investigate the temperature dependence of resistivity in heavy fermion materials. Computations of resistivity are performed using the Memory function formalism. I also explore the behaviour of resistivity in two dimensional ferromagnets tuned near to their magnetic instability. In this case, the calculations are performed using the random phase approximation for the dynamical susceptibility, from which the resistivity is computed. Our calculations are applicable to weakly ferromagnetic systems and to heavy fermion materials.

26Al in AGB grains.

Date: 2021-09-23
Speaker: Dr. Nan Liu, Washington University St. Louis, USA
Venue: Online

Abstract

Presolar grains found in pristine meteorites are stellar relics that predate our solar system. They enable the study of bonafide stellar materials in the laboratory, where the full battery of modern micro-analytical techniques can be brought to bear on them. In this talk, I will present new NanoSIMS isotopic data of presolar SiC grains and discuss their stellar origins and 26Al production in low-mass stars in the light of astronomical observations for carbon stars and stellar models.

The anatomy of the multi-lepton anomalies at the LHC and a candidate for a singlet scalar

Date: 2021-09-20
Speaker: Prof. Bruce Mellado
Venue: Online --> https://bluejeans.com/706821627/1905

Abstract

In this presentation an account of the multi-lepton (electrons and muons) anomalies at the LHC is given. These include the excess production of opposite sign leptons with and without b-quarks, including a corner of the phase-space with a full hadronic jet veto; same sign leptons with and without b-quarks; three leptons with and without b-quarks, including also the presence of a $Z$. Excesses emerge in corners of the phase space where a range of SM processes dominate, indicating that the potential mismodeling of a particular SM process is unlikely to explain them. A procedure is implemented that avoids parameter tuning or scanning the phase-space in order to nullify potential look-else-where effects or selection biases. The internal consistency of these anomalies and their interpretation in the framework of a simplified model are presented. Motivated by the multi-lepton anomalies, a search for narrow resonances with $S\rightarrow\gamma\gamma, Z\gamma$ in association with light jets, $b$-jets or missing transverse energy is performed. The maximum local (global) significance is achieved for $m_S=151.5$\,GeV with 5.1$\sigma$ (4.8$\sigma$).

New Insights into the Gully-fan Formation Processes from the Morphometric Measurements

Date: 2021-09-17
Speaker: Rishitosh Kumar Sinha
Venue: Online

Abstract

Until the past decade or so, gullies on Mars have been thought to have formed from the recent flow of ice/snow melt water. However, some of the recent studies focused on analyzing present-day activity in gullies absolutely denied the role of volatiles (both water and water-ice) for the observed changes in the gullies and rather postulated gullies to have ever formed from a dry process, i.e. by sublimation of dry carbon dioxide ice. While the gullies on Mars have formed over distinct geologic settings such as on crater walls (1) influenced by past glaciation and recent LDM (latitude dependent mantle) cover, (2) influenced by only LDM cover, and (3) without any influence of LDM and glaciation (i.e. fresh gully systems), we argue that the process related to the sublimation of dry carbon dioxide alone cannot explain the formation of the entire gully population. Instead, we suggest that the formative geomorphic processes were different and the underlying material is the culprit. The fresh gully systems typically cut into bedrock, while those with LDM and glacial typically cut in the finer-grained deposits. We suggest this based on our detailed morphologic and morphometric measurement of the gully-fan characteristics that includes estimation of parameters such as melton ratio, fan concavity, fan gradient and alcove length. These parameters were estimated for gullies formed inside 27 craters between 30-60 degrees in Mars' southern hemisphere. Furthermore, we propose that the melton ratio and fan gradient parameters statistically provide a best discrimination of the distinct gully fan types analysed in this study.

Synergy of Neutrino and Dark matter at the advanced particle detector

Date: 2021-09-16
Speaker: Animesh Chatterjee
Venue: Online --> https://bluejeans.com/165045009/1320

Abstract

The predictions of the standard model (SM) have been verified to a remarkable degree of accuracy, but there are still some unanswered questions. Neutrino and dark matter offer great potential for digging out physics beyond the standard model. With the advent of a new generation of advanced neutrino experiments, it is timely to explore physics topics beyond the standard neutrino oscillation. Dark matter phenomenology is turning to more exotic models, neutrino detectors are sensitive to some of those. In this talk, I will discuss the opportunity to explore physics beyond the standard neutrino oscillations, as well as how one can search for dark matter using the same existing setup for neutrino experiment.

Shock-induced incongruent melting of olivine and formation of natural Fe-bearing aluminous bridgmanite in ordinary chondrites.

Date: 2021-09-16
Speaker: Prof. Sujoy Ghosh, IIT Kanpur
Venue: Online

Abstract

The planet Earth was formed from a similar material that constitutes present-day asteroids. Olivine and bridgmanite are the most volumetrically abundant mineral of the Earth’s upper and lower mantle, and it is important to understand its formation mechanism to better comprehend the origin and evolution of planetary interiors. Olivine breaks down to bridgmanite and magnesiowüstite formed by the solid-state or melting of the olivine. Whereas, natural bridgmanites have been reported in only a few shocked meteorites; however, the composition of these specimens differs from plausible compositions of terrestrial bridgmanite. In this presentation, I will present our recent results which show the possible occurrence of bridgmanite and magnesiowüstite formed by incongruent melting of olivine in an ordinary chondrite (Kamargaon L6 chondrite) and the first natural occurrence of bridgmanite, observed in an ordinary chondrite, with a composition closest to the bridgmanite present in the Earth’s lower mantle. The bridgmanite in the ordinary chondrite (Katol L6 chondrite) has high Fe3+/Fe ratio and agrees with experimental predictions. The Katol chondrite may serve as a unique analogue for crystallization of bridgmanite during the final stages of magma ocean crystallization of the Earth.

Next generation 'New' Noble gas mass spectrometer for "single grain" analysis

Date: 2021-09-10
Speaker: Shri Ramakant R. Mahajan
Venue: Online

Abstract

With the discovery of neon isotopes by J. J. Thomson, isotope science came into existence. The noble gas mass spectrometry field flourished from the investigation of returned Lunar samples. New falls of meteorites provide a means of studying the oldest and pristine samples of the solar system. Subsequently, noble gas isotopic studies revealed many secrets of the solar system. e.g. It established the pre-solar origin of "pre-solar grains" from the discovery of anomalous xenon isotopes. The noble gas mass spectrometer at PRL came into established in the decade of seventies. It has gone several folds of new developments for scientific need. Many new results were published from these facilities. e.g. the 'nitrogen isotopes in chondrules' is only available from PRL-NGMS facilities. Now the time has came for next generation of noble gas mass spectrometer facility. In this talk, present status of the existing facilities and the scientific rationale for future requirement of new Noble gas mass spectrometer for single grain analysis will be discussed.

Water, Asteroid and Planet formation: The connections.

Date: 2021-09-09
Speaker: Prof. Maitrayee Bose, Arizona State University, USA
Venue: Online

Abstract

The small bodies in our Solar System and fragments from them, i.e., meteorites can provide vital constraints on planet formation, and the process of volatile acquisition by early formed bodies. Space missions have done successful flybys to several asteroid bodies in the near-Earth space, and in 2005, the Japanese Space Agency’s Hayabusa mission collected samples from an asteroid Itokawa. My team at Arizona State University performed high-spatial resolution, hydrogen isotopic analyses of Itokawa dust grains and their meteorite analogs namely the undifferentiated ordinary chondrite meteorites using the NanoSIMS 50L. We show that undifferentiated, primitive asteroids that form in the inner solar system, close to the Sun are not completely dry, and is likely to provide substantial amounts of water to planets, as the planets grow via collisions. More recent analyses on primitive and differentiated achondrites also shows that these samples also contain substantial amounts of volatiles. I will present the results from ongoing studies in my lab. Two more missions are currently ongoing with the motivation to collect samples from additional small bodies, focusing on highly primitive asteroids rich in organics and water. Japan's Hayabusa2 has successfully collected and brought back ~5 gms of asteroid Ryugu, while NASA's OSIRIS-REx likely collected 100 times more regolith dust from the surface of Bennu. In my talk, I will focus on how my team is preparing for studying samples from asteroids Bennu and Ryugu, and what that can reveal about planet formation.

Various Aspects of Modeling in Astrochemistry

Date: 2021-09-03
Speaker: Dr. Kinsuk Acharyya
Venue: Google meet

Abstract

Molecules are found in a wide variety of astronomical conditions, ranging from star-forming regions to the outer envelopes of carbon stars and from objects in our solar system to distant metal-poor galaxies. The complexity of these molecules ranges from simple diatomic molecules to amino acids such as glycine. Their association with various phases of star and planet formation are of particular interest; they can serve as building blocks of more complex molecules and can provide an insight into the primordial composition of our planet Earth, thereby addressing the issue of “how life originated on Earth”. Besides, they are useful probes of the physical conditions of their environment and related to the lifetime of the sources. Many molecules are not found in the terrestrial conditions that are of interest for what they tell about the build-up of molecular complexity throughout the Universe. Therefore, the study of the formation of these molecules is of paramount importance. In this talk, I will discuss how the formation of these molecules can be studied using numerical simulations in diverse astrophysical sources.

Micrometeorites on the Earth surface: Understanding their origin and properties.

Date: 2021-09-02
Speaker: Dr N G Rudraswami, National Institute of Oceanography (NIO) Goa
Venue: Online

Abstract

Throughout its history planet Earth has been continuously bombarded by high-speed extraterrestrial material. These are debris of comets and asteroids that are leftover material in the solar system, but additional sources may occasionally contribute. The Earth surface accretes a complex variety of these extra-terrestrial material at a rate of approximately 40,000 tons per annum. The dominant size fraction of these extra-terrestrial materials are in the range of few ten of µm to few mm. These sub-mm size particles called as micrometeorites (MMs) provide us an unique opportunity to study diverse collection of samples of solar system bodies in the laboratory. Many micrometeorites have shown textural, chemical, isotopic and trace element composition that can be linked to primitive chondrites such as CI and CM chondrites. Some of these particles are not found in meteorite studies indicate existence of diverse type of precursors in the asteroidal belt that is still not in our inventory. Most dust-sized cosmic particles undergo ablation and chemical alteration during atmospheric entry due to rapid frictional heating, which alters their original properties depending on the size, composition, entry velocity and angle. A comprehensive understanding of this process is essential in order to decipher their pre-entry characteristics. My talk will focus on understanding their chemical and isotopic properties of micrometeorites, that can enhance our overall understanding of these objects.

Grand Unification: Proton Lifetime, Topological Defects, Inflation and Gravity Waves

Date: 2021-08-26
Speaker: Rinku Maji
Venue: Online --> https://bluejeans.com/954481929/5618

Abstract

The Super-Kamiokande (Super-K) experiment sets sacrosanct bounds on the partial lifetime ($\tau$) of the proton decay for different channels, e.g., $\tau(p\to e^+ \pi^0) > 1.6\times 10^{34}$ years which is the most relevant channel to test the viability of the nonsupersymmetric GUTs. The GUTs based on the gauge groups $SO(10)$ and $E(6)$ are broken to the SM spontaneously through one and two intermediate gauge symmetries with the manifestation of the left-right symmetry at least at a single intermediate stage and the proton lifetime for these breaking chains has been computed. The impact of the threshold corrections after integrating out the heavy fields at the breaking scales alters the running of the gauge couplings, which eventually keeps many GUTs off the Super-K bound. Effect of dimension-$5$ operators improves the proton lifetime for specific breaking paths. The stable topological defects can be inflated away if the universe undergoes a sufficient number of $e$-foldings after these defects are formed. We have studied the limit on such breaking scales under the lamppost of GUT inflation using the Coleman-Weinberg potential of a GUT singlet inflaton. We will discuss the generation and subsequent evolution of magnetic monopoles and cosmic strings, as well as the emission of gravity waves from the decaying string loops.

Organics on Itokawa asteroid via analyses of Hayabusa samples.

Date: 2021-08-26
Speaker: Dr Queenie Chan, Royal Holloway, University of London, UK
Venue: Online

Abstract

Understanding the true nature of extra-terrestrial water and organic matter that were present at the birth of our solar system, and their subsequent evolution, necessitates the study of pristine astromaterials. Such investigation necessitates the availability of pristine samples of astromaterials—samples that have not been compromised by terrestrial contamination, and thus preserve the intrinsic states of the materials’ physical, chemical, organic and other properties In this connection, the Hayabusa mission of the Japan Aerospace Exploration Agency (JAXA) is the first asteroidal sample return mission, which has successfully recovered regolith particles from the near-Earth S-type asteroid 25143 Itokawa in 2010. The Hayabusa particles were linked to LL ordinary chondrites based on mineralogy, chemistry and oxygen isotope compositions. Investigation of mineralogy, water and organic contents and other results an Itokawa particle will be discussed.

Realizing flavored leptogenesis: a reappraisal through special kinds of orthogonal matrices

Date: 2021-08-23
Speaker: Nimmala Narendra
Venue: Online --> https://bluejeans.com/846326717/5120

Abstract

The parameterization proposed by Casas and Ibarra in the year 2001 has shown a promising role in the extraction of neutrino Yukawa coupling which is a basic ingredient of the seesaw mechanism generating neutrino mass. We pay special attention in establishing the crucial role of the Casas-Ibarra (CI) parameterization in presence of two different orthogonal matrices, R = O e^{iA} and R = O e^{A} in order to investigate flavored leptogenesis. In the light of these two choices of the orthogonal matrix, we examine the connection between the low energy and high energy CP violations along with certain interesting predictions on the low energy parameters namely, the lightest neutrino mass and the Dirac CP phase (δ). Considering the right-handed neutrino (RHN) mass window to be 10^8 GeV, we show that Dirac phase leptogenesis is possible with the choices of these two orthogonal matrices. We choose a nearly degenerate spectrum for the RHN masses for having a successful leptogenesis. We also emphasize on presenting a range of the matrix elements of the skew-symmetric matrix A. The results obtained in the present analysis underline the importance of understanding the status of CP violation in the low energy sector. We also discuss the phenomenological implications of these two case studies in the context of LFV considering the µ -> eγ decay process.

Heating of the solar chromosphere by acoustic waves

Date: 2021-08-20
Speaker: Dr. Michal Sobotka, Astronomical Institute of the Czech Academy of Sciences, Ondrejov, Czech Republic
Venue: Online

Abstract

Acoustic and magnetoacoustic waves play an important role in the chromospheric heating, exhibiting the capability of depositing a main part of their energy in the chromosphere. To study the heating of solar chromospheric magnetic and non-magnetic regions by acoustic and magnetoacoustic waves, the deposited acoustic-energy flux, derived from observations of strong chromospheric lines (Ca II 854.2 nm, H-alpha, H-beta, and Mg II k & h), is compared with the total integrated radiative losses. A set of quiet-Sun and weak-plage regions was observed with the Dunn Solar Telescope (DST), Vacuum Tower Telescope (VTT), Goode Solar Telescope (GST), and Interface Region Imaging Spectrograph (IRIS). The deposited acoustic-energy flux is derived from Doppler velocities observed at two different reference heights corresponding to the middle and upper chromosphere. A set of scaled non-LTE 1D hydrostatic semi-empirical models, obtained by fitting synthetic to observed line profiles, is applied to compute the radiative losses. In the quiet chromosphere, the deposited acoustic flux is sufficient to balance the radiative losses and maintain the semi-empirical temperatures in layers between the two reference heights. In the magnetic active-region chromosphere, the contribution of magneto-acoustic energy flux to the radiative losses is only 10–30 %, too small to balance the radiative losses in the active chromosphere, which has to be heated by other mechanisms.

Importance of second oscillation maxima in probing invisible neutrino decay

Date: 2021-08-19
Speaker: Kaustav Chakraborty
Venue: Online --> https://bluejeans.com/116266679/4331

Abstract

The constraints on invisible neutrino decay can come from future planned/proposed long baseline experiments - T2HK/T2HKK and ESSνSB. The T2HKK and ESSνSB experiments are both designed to have energy peak near the second-oscillation maximum of Pμe while T2HK has the energy peak at the first oscillation maximum of Pμe. We perform a full three flavour study using matter effect and obtain the sensitivity to τ3/m3 for these experiments. In particular, we investigate how the experiments at first and second oscillation maximum fare in presence of neutrino decay. We also study the important factors on which the measurement of θ23 can depend in presence of decay. We have found that in presence of decay, the overall octant sensitivity is enhanced. This can be attributed to the octant sensitive contribution coming from the disappearance channel (Pμμ) in presence of neutrino decay.

Origin of the solar system

Date: 2021-08-12
Speaker: Prof. Sandeep Sahijpal, Punjab University
Venue: Online

Abstract

Sputtering of Presolar Grains via Galactic Cosmic Rays in the Interstellar Medium

Date: 2021-08-06
Speaker: Mr. Vikram Goyal
Venue: Online

Abstract

Circumstellar grains condensing in cooling circumstellar disk/envelopes of stars are ejected into the interstellar medium (ISM) during events like mass loss or the death of stellar objects. Asymptotic giant branch (AGB) stars typically lose around 10 −6 M סּ yr −1 during regular mass-loss events, whereas supernova (SN) events usually taking place only twice or thrice in a century are the major contributor to the ISM's dust. The abundance of circumstellar grains in the ISM is only ∼1% of the total dust; however, the absolute mass compared to the mass of the protoplanetary disk is enormous, thus making it essential. When in the ISM, presolar grains tend to grow an ice mantle over the surface due to their interaction with gas molecules at low temperatures. Concurrently, the ISM also acts as a harsh medium, and the grains are either partially or entirely modified/destroyed during their interstellar lifetimes. Destruction and formation or re-accretion of the grains is a continuous process in the ISM. Galactic cosmic rays are one of the possible Ways of dust destruction. So, I will be discussing the sputtering of the grains due to the galactic cosmic rays. Also, I will talk about the role of the ice mantle in the destruction of grains.

Exploring the signature of non standard interactions in long baseline neutrino experiments

Date: 2021-08-04
Speaker: Supriya Pan
Venue: Online --> https://bluejeans.com/239534349/0818

Abstract

We have ventured a lot into the paradigm of neutrino oscillation, governed by mass squared differences between neutrino states and mixing. Most of these parameters are now well determined and for the measurement of the remaining parameters many high statistics experiments are planned. These experiments also provide the opportunity to explore imprint of of new physics in neutrino oscillations. We have studied the effect of non- standard interaction on neutrino oscillation probabilities during their propagation through Earth's matter. We focus on the conversion probability of muon to tau neutrinos. In the simple two-generation case the probability $P_{\mu\tau}$ is not affected by interactions of neutrinos in matter. But for three generation case at baselines of the order of 9000 km there are matter effects affecting this channel. This is considered a genuine three flavour effect. We study how the presence of non-standard interaction alters the $P_{\mu\tau}$ probability at these baselines. We observe large deviations from standard matter effect , which indicates presence of new physics to be probed in upcoming experiments.

Probing the inert doublet model in next-to-leading order QCD at the LHC

Date: 2021-08-04
Speaker: Anupam Ghosh
Venue: Online --> https://bluejeans.com/536192538/2721

Abstract

LO analysis of the IDM model in the hierarchical mass spectrum is well studied. The IDM model gives a viable dark matter (DM), and hierarchy mass spectrum means DM mass is low and heavy scalars have the mass of the order 100 GeV larger than DM. We will take one order alpha_s correction of the IDM Lagrangian along with gluon gluon Higgs effective Lagrangian. When a pair of pseudoscalars is produced, the k-factor in all the benchmark points is greater than 1.7. Pair of DM annihilates into SM particles through Higgs boson mediator is the only annihilation channel in low DM mass regime, and this channel has a k-factor of 1.86. So it is essential to include the NLO correction to get an actual description. In this study, after taking one order correction of the total Lagrangian, we study the jets+MET signal. Di-fatjet+MET signal looked previously at LO accuracy. We explore this difatjet +MET signal with NLO accuracy and shown that if one considers only LO, then 1J_V + MET signals are overproduced, and 2J_V + MET is underestimated. With NLO accuracy, we show that the significance improves in the cut-based analysis.

Non-Radial Oscillation modes in Hybrid Stars: Consequence of Mixed Phase

Date: 2021-08-03
Speaker: Deepak Kumar
Venue: Online --> https://bluejeans.com/678749840/7882

Abstract

Neutron stars are interesting laboratories to study matter at high densities. At high densities (of the order of 3 to 4 times nuclear matter density), the normal confined nuclear matter is expected to undergo the phase transition to deconfined quark matter. It is expected that neutron stars might contain deconfined quark matter in the inner core and nuclear matter in the outer core. In this talk, I will discuss the phase transition from nuclear matter to quark matter at high densities with a possibility of a mixed phase. I will also discuss the consequences of the mixed phase in the core of neutron star/hybrid star in the context of mass radius relation. Finally I will present some results on the non-radial oscillation modes in such stars.

Singlet Doublet Freeze-in dark matter in the presence of (non-)standard cosmology

Date: 2021-08-02
Speaker: Sudipta Show
Venue: Online --> https://bluejeans.com/593904063/3558

Abstract

Decades of null results from different direct detection experiments for dark matter keep suggesting that the weakly interacting massive particle(WIMP) paradigm may need a relook for the theory of particle dark matter. The non-thermally produced freeze-in dark matter is an exciting and alternative proposal. It naturally explains the non-observation of any signature because of its feeble interaction with the standard model particles. We consider a simple extension of the standard model with a pair of fermions, one singlet, and doublet to incorporate dark matter. We discuss the freeze-in production of dark matter in the context of the singlet-doublet model. Also, we talk about the effect of the fast expansion of the Universe on the dark matter phenomenology.

Mechanical Design of LPEX(Langmuir Probe) sensors for MOM-2

Date: 2021-07-30
Speaker: Mr. Kalyana Srinivasa Reddy
Venue: Online

Abstract

Langmuir probe experiments have been traditionally employed to characterize the laboratory plasmas since their first development by Irving Langmuir. Due to its simplicity, the Langmuir probes have been flown onboard several interplanetary missions to characterize the ionospheric plasma of different planetary bodies. However, the plasma in the planetary ionospheres poses complex scenarios as compared to a laboratory plasma. Being exposed to the plasma, the probe experiences harsh environments, and the probe has to be designed so as not to interfere with the plasma nor be degrade/damaged by it. These intricate conditions will be presented and their influence on the mechanical design of the Langmuir probe, which is being developed for the LPEX payload of the MOM-2 mission, will be discussed. An algorithm was also developed to derive the plasma characteristics from an I-V curve. This algorithm is tested using the MAVEN's LPW (I-V) data and the results are compared to those of the MAVEN's derived characteristics. The results and the algorithm will also be presented in the discussion.

Radiative Leptonic Decays of Kaons and Light Cone Sum Rules

Date: 2021-07-30
Speaker: Anshika Bansal
Venue: Online --> https://bluejeans.com/824628878/0559

Abstract

The leptonic decays of pseudoscalar mesons (kaon, pion, etc) are essential ingredients for extraction of CKM matrix elements. In the standard model, these decays are helicity suppressed. The helicity suppression can be lifted by considering the radiative leptonic decays which show an interesting pattern for the case of kaons. The radiative decay also helps in understanding the dynamics of strong interaction via two transition form factors (FFs): vector (V) and the axial vector (A) FF. The study of these FFs became more interesting after a recent publication (arXiv: hep-ph/2012.02120) which has reported significant differences between the lattice and experimental results for values of (V+A) and (V-A). We have attempted to compute these FFs (in particular for $K^- \rightarrow \ell^- \nu_\ell \gamma$) in the framework of light cone sum rules (LCSR) upto twist-4 accuracy. In this talk, I will discuss the computation of these FF in LCSR and the challenges involved along with the preliminary results.

Triggering of solar eruptions and their large-scale consequences

Date: 2021-07-30
Speaker: Mr. Suraj Sahu, SRF, USO/PRL
Venue: Online

Abstract

Solar eruptions are spectacular magnetic explosions in the Sun’s corona. These explosive events manifest themselves in the forms of filament eruptions, flares, and coronal mass ejections (CMEs) which are collectively termed as solar eruptive events. Decades of studies on these eruptive events have revealed that a common physical process must be the driver mechanism behind all these phenomena. The physical process involves disruption and reconfiguration of the coronal magnetic field, which ultimately leads to an ejection of magnetized plasma. However, even though eruptions have been observed extensively for many years, the specific build-up and trigger mechanisms remain rather elusive. Due to the wide variety of pre-eruptive magnetic configurations, various trigger mechanisms have been proposed. Once the eruption is triggered, it either erupts successfully from the solar atmosphere leading to a CME or contained by the restraining overlying magnetic field to be termed as confined eruption. In this talk, I will discuss about some mechanisms responsible for the triggering of solar eruptions. These works involve extensive analysis using multi- wavelength and multi-instrument solar observations. I will specifically focus on the eruptive features leading to CME. The large-scale aspects in the course of their evolution in the solar corona will also be discussed.

Self Consistent Renormalisation (SCR) Theory of Itinerant Magnetism

Date: 2021-07-29
Speaker: Bharathiganesh D.
Venue: Online --> https://bluejeans.com/126889001/4341

Abstract

Understanding Itinerant electron magnetism has always been a matter of interest as it holds the key for understanding magnetism in metals like Iron, Nickel Cadmium. Recently there has been synthesis of many heavy Fermion compounds and anti ferromagnets which are expected to be itinerant magnets and this has kindled the interest further in the subject. Self Consistent Renormalisation (SCR) theory is the best among the available theories for itinerant magnetism, whose predictions agree well with experiments. In this talk we will discuss the SCR theory in detail. We will also discuss the results of numerical calculations that we have obtained in order to show the level of accuracy to which the predictions of SCR theory hold true in the regime of itinerant magnetism.

Radiative transfer modeling to explain the observed line profiles of a hot molecular core

Date: 2021-07-29
Speaker: Bratati Bhat
Venue: Online / Zoom

Abstract

The low mass star formation process is well studied, and the evolution process is comparatively well established. But, it is still unclear whether the massive star also follows a similar process or it goes through a completely unconventional way. In this attempt, we made a detailed observational analysis of a well-known hot molecular core lying in the high-mass star-forming region G31.41+0.31 with the ALMA. We observe an inverse P-Cygni profile (representative of the infalling envelope) towards this source. Many other complex organic molecules are also observed towards this source. In my presentation, I will explain this source's detailed radiative transfer modeling to explain the observed line profiles.

Topological Properties of Three-dimensional Magnetic Null

Date: 2021-07-29
Speaker: Mr. Yogesh Kumar Maurya, JRF, USO/PRL
Venue: Online

Abstract

Three dimensional magnetic null points are one of the potential sites for the magnetic reconnection. They are responsible for the eruptive events like solar flares, jets, coronal mass ejections occurring in the solar corona. In this presentation, the local configurations of three-dimensional magnetic null points are investigated by a linear analysis about the magnetic null point. The configurations are first classified as either potential or non-potential depending on the electrical current as a parameter. Then in non-potential cases the role of the electrical current as a parameter is discussed. In non-potential case the two component of current, one which is parallel to spine determines the spiral nature of field lines near the null while the other component which is perpendicular to the spine affects the inclination of the fan plane to the spine. Further, depending on the sign of real part of the eigenvalue of Jacobian matrix, which is obtained when we do first order Taylor’s expansion of the magnetic field near the null. The sign of the real part of eigenvalues of the Jacobian matrix determines the direction of the field lines. The topological degree is assigned as +1 or -1 depending on the direction of the magnetic field lines of either spine or fan towards the magnetic null point. For an example, if the Magnetic field lines of the spine axes are directed towards the magnetic null point, then the topological degree of magnetic null is +1 and vise-versa. Subsequently, we explore the concept of the net topological degree conservation of three-dimensional magnetic null point in both the cases in ideal as well as in resistive plasma, which can be exploited to understand the sympathetic flaring.

Fractional Quantum Hall states on Optical Lattices

Date: 2021-07-28
Speaker: Deepak Gaur
Venue: Online --> https://bluejeans.com/536889561/0706

Abstract

The studies pertaining to the Quantum Hall (QH) effect and QH states constitute an active area of research. In condensed matter systems, the observation of the QH states is difficult, as they require very high magnetic fields (~ 10 Tesla). Instead, ultracold atoms in optical lattices are useful systems as synthetic magnetic fields of high magnitude can be generated in these systems. In this talk, we shall discuss about the study of the QH effect and realization of the synthetic magnetic field in a system of charge neutral bosons in optical lattices. We shall also discuss various properties of the QH states and in particular the calculation of the Many body Chern number which characterises the topological order of QH states.

The Secrets of Sunspot Penumbra and a Status Description of the European Solar Telescope

Date: 2021-07-27
Speaker: Dr. Rolf Schlichenmaier, Leibniz-Institut für Sonnenphysik (KIS), Freiburg Germany
Venue: Online

Abstract

I will review our understanding of sunspots confronting theoretical modelling with key observations. Sunspots consist of two distinct stratifactions that are manifested in the photosphere as umbra and penumbra. Only recently, it was found that the photospheric boundary between umbra and penumbra, hitherto defined by an intensity threshold, can be determined with a threshold value for the vertical component of the magnetic field strength (Jurcak 2011). As it turns out, ‘realistic’ sunspot simulation that nicely reproduce the intensity morphology and flow field geometry of observed sunspots (Rempel 2011) fail in reproducing the topology of the magnetic field (Jurcak et al. 2020). At KIS (in collaboration with M. Rempel), we succeeded in setting up intial and boundary conditions that lead to a numerical sunspot model that has the proper photospheric properties, but this leads to another unsolved riddle... In a second part of the talk, I will present the goals and status of the European Solar Telescope. The second edition of the Science Requirement Document was published in the end of 2019 describing the scientific objectives of EST that infer from the main theme to study the fundamental MHD processes of the solar atmosphere at its intrinsic scales. A major recent technical development allows to have the 2nd mirror as an adaptive mirror, which resulted in an optimised optical design of only 6 mirrors (instead of 14 in the old design). I will also address the conceptual design of the EST instrument suite that is currently under way.

Higher order precision calculations in QCD and N=4 SYM

Date: 2021-07-26
Speaker: Dr. Maguni Mahakhud
Venue: Online --> https://bluejeans.com/790912493/3405

Abstract

As the experimental accuracy of different observables is increasing day by day at different colliders, precise theoretical predictions become very important. The Large Hadron Collider (LHC) plays a very important role in confirming the Standard Model (SM) of Particle Physics and constraining Beyond Standard Model (BSM) physics. Since LHC is a hadron collider, Quantum Chromodynamics (QCD) corrections are very important in calculating different observables. These calculations become very difficult due to the increasing number of loops and external legs. So far, many techniques have been developed to handle these difficulties and many more are in the developmental process. I will explain some of such techniques used in calculating higher order corrections in this talk. Also these QCD amplitudes contain universal infrared divergence structures and N=4 SYM often captures large chunks of full QCD computations. The high symmetry of N=4 SYM sometimes helps to get a cleaner view on fundamental features that may remain hidden in QCD for its additional complexity. Similarities of QCD observables with N=4 SYM could be the indications to undiscovered hidden symmetries. I will discuss on such universal structures of QCD and N=4 SYM amplitudes.

Role of magnetoacoustic waves in chromospheric heating

Date: 2021-07-26
Speaker: Mr. Hirdesh Kumar, SRF, USO/PRL
Venue: Online

Abstract

The complete understanding of the chromospheric heating still needs investigation. There are two competing theories that have been proposed to explain the heating of solar atmosphere : (1) mechanical heating by upward-propagating waves (Alfven 1947, Schwarzschild 1948, Stein 1972), and (2) Joule heating associated with the magnetic field reconnection (Parker, 1988) and resistive dissipation of electric currents (Rabin & Moore, 1984). Albeit, some studies have ruled out high frequency (>5.2 mHz) acoustic waves (Fossum & Carlsson, 2005), magnetic reconnection & electric currents (Socas-Navarro, 2005) as being too weak to heat the solar chromosphere. Earlier studies (Jefferies et al. 2006, Rajaguru et al. 2018) show that low-frequency acoustic waves (2-5.2 mHz) can also propagate into solar atmosphere along inclined magnetic fields, and thereby can contribute to the heating of the solar atmosphere. In this talk, I will discuss observational aspects of the propagation of low-frequency acoustic waves into the solar chromosphere in the magnetic network regions using the observations from MAST facility of USO.

Effect of metallicity in the atmospheric composition of Exoplanets

Date: 2021-07-23
Speaker: Mr. Vikas Soni
Venue: Online

Abstract

Planets outside the solar system are known as exoplanets. From the first discovery of exoplanets in 1992, the confirmed exoplanets count climbed to more than 4100. Statistical and observation data suggest that each star has at least one exoplanet around it, making sure that a large number of exoplanets are present in the observable universe. This large set of exoplanets have a vast range of parameters (Temperature, size, orbital properties, chemical parameters, metallicity, hosting star). In several ways, these parameters affect the atmospheric composition of these exoplanets, especially the composition of the atmosphere. Increasingly, many molecules are found in the atmosphere of exoplanets. In the presentation, first, I will give a brief account of observations of these molecules. Then will discuss how the abundance of these molecules will change with metallicity. We considered both equilibrium and disequilibrium processes. We took three test exoplanets with different parameters and studied their chemical abundance for a range of atmospheric metallicity. Also, I tried to understand possible observational effects of enhanced/reduced metallicity.

CMEs associated with DH type II bursts and their Sun-Earth propagation

Date: 2021-07-20
Speaker: Ms. Binal Patel, SRF, USO/PRL
Venue: Online

Abstract

It is well accepted that the type II solar radio bursts are caused by magneto-hydrodynamic shocks which propagate through the solar corona and interplanetary medium. Type II bursts are associated with flares and coronal mass ejections (CMEs), hence their investigations provide important insights toward understanding the influence of transientsolar activity on the corona and heliosphere. We present the characteristics of decameter-hectometer (DH) type II bursts for the Solar Cycle 23 and 24. For the present study, we have classified the bursts according to their end frequencies into three categories, i.e. Low Frequency Group (LFG; 20 kHz <= f <= 200 kHz), Medium Frequency Group (MFG; 200 kHz < f <= 1 MHz), and High Frequency Group (HFG; 1 MHz < f <= 16 MHz). Our analysis shows a drastic reduction of the DH type II events during Solar Cycle 24 which includes only 35% of the total events (i.e. 179 out of 514). Despite having a smaller number of DH type II events in the Solar Cycle 24, it contains a significantly higher fraction of LFG events compared to the previous cycle (32% versus 24%). However, within the LFG group the cycle 23 exhibits significant dominance of type II bursts that extend below 50 kHz, suggesting rich population of powerful CMEs travelling beyond half of the Sun-Earth distance. Our analysis also indicates that CME initial speed or flare energetics do not have direct link with duration of DHtype II bursts. The profiles relating CME heights with respect to the end frequencies of DH type II bursts suggest that for HFG and MFG categories, the location for majority of CMEs (~65%–70%) is in well compliance with ten-fold Leblanc coronal density model, while for LFG events a lower value of density multiplier (~3) seems to be compatible. We further studied the Sun-Earth propagation characteristics of interplanetary CMEs (ICMEs) arriving at 1 AU that are associated with DH type II radio bursts (type II ICMEs). We provide a detailed comparison of ICME parameters (mean ICME speed, magnetic field) at 1 AU along with Sun-Earth propagation parameters (transit time, acceleration) between the type II and non-type II ICME groups. Our results confirm that the ICME characteristics at 1 AU primarily depend on near-Sun CME characteristics and solar wind conditions in the interplanetary medium. However, to understand complex cases effectively in near-Earth space weather, the analysis needs to be made on a case to case basis and should include the possibilities of CME-CME and CME-corotating interaction region (CIR) interactions.

Self Consistent Renormalization (SCR) Theory of Itinerant Magnetism

Date: 2021-07-19
Speaker: Dr. Akariti Sharma
Venue: Online --> https://bluejeans.com/162793618/8011

Abstract

We theoretically investigate the effects of electron correlation on itinerant magnetism by using the Self Consistent Renormalization (SCR) theory. It is found that this theory is quite successful in approximating the Curie-Weiss like behavior of the temperature dependence of the magnetic susceptibilities above the Curie temperature Tc: widely observed in ferromagnets, weak ferromagnets or even in metallic magnets. Our work is mainly focused on the point to explain the Curie-Weiss like behavior in aforementioned magnets because the necessary condition for this behaviour is not known yet. To calculate dynamical susceptibilities, additional free energy as a function of magnetization is expressed in terms of transversal dynamical susceptibilities which are calculated by employing the modified random phase approximation. Further the properties of spin fluctuations are also explored along with the approximate prediction of Tc. It is found that spin fluctuations are important in understanding the true cause of magnetism in such magnets. However, there are several reported difficulties with the SCR theory in calculating the exact value of spin fluctuations and Curie-Weiss susceptibilities. Most of them are settled now and we are planning to apply this theory to study thermodynamic properties of realistic magnets in comparison with experimental data.

Compositional diversity of comets and gas phase coma modelling

Date: 2021-07-16
Speaker: Ms. Sana Ahmed (SRF-PSDN)
Venue: Online

Abstract

Comets are made up of left-over material that formed the planets, and they are also the least-altered objects surviving from the protoplanetary disks that formed the solar system. While comets in the solar system provide an understanding of the solar system formation, recent observation of the interstellar comet 2I/Borisov provides a unique opportunity to understand the physical conditions that prevailed in a distant unknown planetary system. Comet 2I/Borisov was discovered by G. Borisov on August 30, 2019. The water production rate for this comet is measured with a peak value of 10 ± 1.1 × 10^26, while the CO production rate is found to be between 4.4 ± 0.7 × 10^26 and 10.7 × 10^26. This makes comet 2I to be significantly CO rich and the CO/H2O ratio can be as high as 178%. The typical values of CO/H2O for solar system comets ranges between 1.4% to 8.8%, which makes 2I/Borisov a notable exception when compared with the solar system comets. In solar system comets a large number of species are observed in the cometary coma, therefore it is pertinent to ask what chemical diversity is expected to be seen in the ISM comet. Also, how are the abundances of secondary and tertiary species affected when CO production rate is comparable/more to that of water. We have used a combined hydrodynamic and chemical model to study the chemical evolution of the coma of 2I/Borisov. In this talk, I will discuss the general volatile composition of solar system comets and of 2I/Borisov, followed by some of our model results.

Deciphering the water source utilization and transport by plants using stable isotopes

Date: 2021-07-13
Speaker: Ms. Ajayeta Rathi
Venue: Online Platform (Bluejeans)

Abstract

Plants play a major role in global hydrological cycle controlling ecosystem, climate, and natural resources. Water present in plants is mainly transported by a vascular tissue called xylem, which also transports nutrients from the root to the rest of the plants and provide structural support to them. Xylem water also play a major role in plant physiology and plants have the tendency to use different sources of water with respect to its availability. So tracing the isotopic signature of xylem water will provide better insights about utilization of water by plants in a given area. Further, temporal and spatial change in plant species composition and physiology is mainly driven by the climatological settings and hence there is likelihood of differences in water use efficiency and transport mechanism. Considering the above background, in this talk, I will discuss about the importance of stable isotopes in xylem water as a tool to understand water transport in plants.

Lunar meteorites as proxy to understand the lunar evolution

Date: 2021-07-09
Speaker: Mr. Yash Srivastava (SRF-PSDN)
Venue: Online

Abstract

The story of lunar evolution was written soon after the Apollo 11 mission. In the intervening ~50 years since its inception, the Lunar magma ocean (LMO) has been the paradigm under which all the lunar data, obtained from sample or otherwise, have been interpreted. Laboratory and remote sensing data have revealed that region from which the Apollo and Luna obtained the rock and soil samples is unusually enriched in incompatible trace elements (ITEs), i.e., Th and U. Therefore, the returned lunar samples are not the representative of the global Moon. Lunar Meteorites offers us to look into the unexplored regions, which have not been sampled by the Apollo and Luna Missions as they were possibly ejected from the lunar surface and subsurface by impacts at random locations on the Moon. Although mare basalts have provided enough to understand the internal structure and evolution of the Moon, studies on the lunar meteorites have raised some important new debates. E.g., the anti-correlation between Ti and age of VLT lunar meteorites reveals the complex nature of the Moon. In this talk, I shall briefly discuss a few unanswered questions about the lunar evolution. This will be followed by discussion of some preliminary results that I have obtained for a VLT lunar meteorite along with my future research plan to answer those questions.

Reconstruction of ocean deoxygenation using Iodine/Calcium (I/Ca) ratios in marine carbonates

Date: 2021-07-06
Speaker: Mr. Deepak Kumar Rai
Venue: Online Platform (Bluejeans)

Abstract

Oxygen is an essential element for all the heterotrophic organisms in the oceans. Decrease in the ocean oxygen levels has been observed since the middle of the 20th century. This ocean deoxygenation ranks among the most important changes occurring in marine ecosystems. The oxygen content of the ocean constrains productivity, biodiversity, and biogeochemical cycles. Major extinction events in the Earthâ€™s history have been associated with warm climates and oxygen-deficient oceans, and under current trajectories, anthropogenic activities could drive the ocean toward widespread oxygen deficiency. The current climate models and observations generally agree on the loss of oxygen from the oceans. But these models tend to underestimate oxygen spatial variability and temporal trends, especially in the tropical thermoclines. This disagreement between models and observations is problematic for future predictions, as these regions host large open ocean oxygen minimum zones (OMZs), where a further decrease in oxygen levels could have large impacts on ecosystem and biogeochemistry. In such a case, reconstruction of the ocean deoxygenation from the geological past may provide insight into future deoxygenation. For such long-term predictions, a geochemical proxy is required to reconstruct past oxygen levels. One such proxy is Iodine/Calcium (I/Ca) ratios in foraminifera. In this talk, I shall discuss how past ocean levels are reconstructed using I/Ca ratios in foraminifera.

Solar eruptive event as an Initial Value Problem

Date: 2021-07-06
Speaker: Mr. Satyam Agarwal, JRF, USO/PRL
Venue: Online

Abstract

Coronal magnetic field extrapolations are necessary to understand the magnetic field topology of the source region in solar coronal transients. There are various extrapolation models, broadly classified into non force-free or force-free—depending on whether the model allows for a non-zero Lorentz force or not. Presently, these models are employed to carry out data-driven and data-constrained magnetohydrodynamics (MHD) simulations to explore the underlying magnetic reconnection (MR). It is then imperative to study the dependence of the simulated evolution on the particular extrapolation model used. The focus is that with MRs—a dissipative-process—being responsible for the transients, evolution from two different initial extrapolated fields would not differ since, presumably the dissipation erases the memory. The paper addresses this novel question by comparing numerical simulations of active region NOAA 11977, hosting a C6.6 class eruptive flare, initiated from non force-free and force-free initial fields. For MHD simulations, we employ the EULAG-MHD model which allows for MRs in the spirit of Implicit Large Eddy Simulations (ILESs) while preserving the condition of flux-freezing away from reconnection sites. We find that both the extrapolations yield good agreement with the observed line of sight magnetic field while non force-free field (NFFF) shows a higher degree of correlation with the transverse component compared to non linear force-free field (NLFFF). Nevertheless, broadly, the differences between the two extrapolated fields are not vastly different, except at the neighborhood of three dimensional (3D) magnetic nulls. Further, the topological comparison suggests that most of the magnetic field line structures are reproducible in both the models, although the extent of the agreement between the two varies. Importantly, the MHD simulations suggest the magnetic field lines (MFLs) undergoing MRs evolve similarly, reconnection details being nearly independent of the models—as theorized upfront. Consequently, both extrapolation techniques are suitable for initiating data driven and data-constrained simulations.

Fine grained rim mineralogy and Iron oxidation record in carbonaceous chondrites

Date: 2021-07-02
Speaker: Ms. Shivani Baliyan
Venue: Online

Abstract

Fine-grained materials occur as rims around various coarse grained components, such as CAIs, chondrules and isolated mineral fragments. Fine-grained rims (FGRs) contain secondary minerals formed due to aqueous alteration of anhydrous precursor phases. However, the origin and modification of FGRs is poorly understood. Debate currently exists whether the alteration of FGR occurred in nebular condition or in the parent body setting. Nevertheless, FGR is important for shedding light on the chemistry and accretionary history of chondritic material in the early solar system. Further, the composition of matrix in CM chondrite comprises hydrous phases which include Mg-rich serpentine to Fe-rich serpentine and their relative abundances largely depend upon the degree and extent of the aqueous alteration. During the alteration, the majority of anhydrous silicates, metal and sulphide through dissolution and replacement transform into secondary phyllosilicates and Fe-oxides. In this process, Fe (0 or +2) is transformed into Fe3+ bearing phases and thus the valence of Fe becomes a useful tracer for quantifying the aqueous alteration. In this study, I shall discuss the chemistry of FGR and its alteration effect, comparison with matrix and finally iron speciation to explain the redox state of the phyllosilicate of Mukundpura meteorite (CM2). This study will be useful to assess qualitative and quantitative alteration of CM chondrite.

Surface & subsurface oceanography of the Equatorial Indian Ocean: New insights from Thermocline variation study

Date: 2021-06-29
Speaker: Mr. Sanjit Kumar Jena
Venue: Online Patform (Bluejeans)

Abstract

The equatorial Indian ocean (EIO) region is unique in nature in terms of its geography and oceanographic settings compared to other global oceans. Unlike the Pacific and Atlantic, being land locked in the north restricts its northward spread. This characteristic distribution of ocean and subcontinent near to the equatorial regime has helped develop a distinct and dynamic climatic pattern attributed to this region, where mutual interaction of ocean and atmosphere govern the regional climate. Numerous studies carried out so far in the region mostly addressed the understanding of the evolution of EIO climate over time and its implications to the global climatology. While most of the studies are limited to the surface oceans, very little is known about the intermediate levels. The Indian Monsoon plays a major role in governing the surface ocean hydrology with smaller contributions from the terrestrial influxes and upwelling. In principle, the thermocline water of the EIO has three sources: (i) the intimately linked Subantarctic Mode and Antarctic Intermediate Waters (SAMWâ€“AAIW), (ii) the Indonesian Intermediate Water (IIW) from the Indonesian Throughflow, and (iii) combined Persian Gulf and Red Seawaters (PGWâ€“RSW). While, the highly saline and O2-poor PGW and RSW contribute to local intermediate water formation, their combined volume is one order of magnitude lower than the southern source. Evidence of Antarctic Intermediate waters on the EIO temperature have been reported recently, adding a new dimension to the existing understanding. The variations in AMOC strength appear to be an important driver of the thermocline structure in the tropical Atlantic from annual to multi-millennial time scales. Thus, understanding the role of oceanic thermocline and its response to subsurface variations over time would provide better clue. Our study attempts to address this issue based on isotopic data of the planktonic foraminifera shells from the EIO thermocline region.

Design aspects and Development of Neutral and Ion Mass Spectrometer (NIMS)

Date: 2021-06-25
Speaker: Mr. Amogh Auknoor
Venue: Online

Abstract

In the past few decades, we have observed a rapid proliferation of Mass Spectrometers in various areas of research. Though they have been used extensively for laboratory and ground-based purposes, their true potential was realized in their ability to investigate planetary atmospheres. Mass spectrometers expedited the process of evaluating a planetary atmosphere’s likeness to that of the Earth and eventually helped researchers estimate the possibility of life. Thus, Mass spectrometers have been part of our space heritage. In this seminar, I shall discuss a brief history of how mass spectrometers evolved and their types. While being very simple in its structure, a Quadrupole Mass Spectrometer(QMS) is very complex and dynamic in its behavior. First, I shall dive into the theory behind the design of a QMS. Next, we shall understand how a QMS can function as both a continuous mass-analyzer and a trap. Finally, I shall conclude with a brief update on the status of different versions of PRL’s in-house Neutral and Ion Mass Spectrometers (NIMSs).

Alpha Particle Spectrometer (APS) for future mission on the Moon

Date: 2021-06-18
Speaker: Mr. Sushil Kumar
Venue: Online

Abstract

It is proposed to develop an Alpha Particle Spectrometer (APS) for the upcoming ISRO-JAXA mission to study the volatile transport on the Moon. The existence of permanently shadowed areas in the polar regions of the moon implies that these areas can act as cold traps for water molecules and other volatiles that will be transported from the hot sunlit side of the moon to these colder areas. The proposed APS instrument is aimed to detect 5.49 MeV and 5.304 MeV alpha particles from radioactive decay of 222Rn and 210Po near permanently shadowed areas in the lunar polar region. This detection will help us in understanding the transport of volatiles on the lunar surface. In this direction, we have established an APS experiment in the laboratory and is being used for various experimental purposes with samples and radio-active sources. This presentation gives an overview of the proposed instrument, its design aspects and laboratory experiment based on alpha spectroscopy.

Constraint on primordial magnetic fields in the light of ARCADE 2 and EDGES observations

Date: 2021-06-17
Speaker: Pravin Kumar Natwariya
Venue: Online --> https://bluejeans.com/335834835/9609

Abstract

We have studied the upper constraints on primordial magnetic fields (PMFs) in the light of the Experiment to Detect the Global Epoch of Reionization Signature (EDGES) low-band observation and Absolute Radiometer for Cosmology, Astrophysics and Diffuse Emission (ARCADE 2). ARCADE 2 observation detected extra-galactic excess radio radiation in the frequency range 3-90 GHz. The enhancement in the radio radiation is also supported by the first station of the Long Wavelength Array (LWA1) in the frequency range of 40-80 MHz. The presence of early radiation excess over the cosmic microwave background can not be completely ruled out, and it may explain the EDGES anomaly. In the presence of decaying PMFs, 21 cm differential brightness temperature can modify due to the heating of the gas by decaying magnetic fields, and we can constraint the present-day strength of the primordial magnetic fields.

Langmuir Probe electronics for LPEX payload for future Mars mission: Design and developmental aspects

Date: 2021-06-11
Speaker: Mr. Chandan Kumar
Venue: Online

Abstract

Langmuir Probe and Electric Field Experiment (LPEX) will investigate the Electron density, electron temperature and electric fields in the ionosphere and exospheric regions of Mars. The experiment has two parts 1) Langmuir Probe (LP) and Electric Field (EF), which deals with a design of measurement of precise, very low orders of currents and potentials, respectively. LP works by immersing one or multiple electrodes in plasma which is biased to time-varying potential between them. An electron or ion current is measured. This measured ion and electron current is used to determine electron temperature and density. The design aspects of Langmuir Probe electronics and its current development will be discussed in the seminar.

Multi-wavelength observations and coronal magnetic field modeling of complex cases of circular ribbon flares

Date: 2021-06-10
Speaker: Mr. Prabir K Mitra, SRF, USO/PRL
Venue: Online

Abstract

Circular ribbon flares are characterized by the circular, quasi-circular or elliptically shaped chromospheric ribbon brightening. Such flares occur from the so-called ‘anemone’ type active regions which are identified by photospheric magnetic configurations where a magnetic patch of one polarity is surrounded by opposite polarity magnetic flux regions. The associated complex coronal arrangement involves a fan-spine configuration in a null point topology. In most of the circular ribbon flares, onset of a set of parallel ribbons are observed prior to the onset of the circular/quasi-circular ribbon brightening that surrounds the parallel ribbons. On the basis of such observations, a general understanding on the circular ribbon flares has been developed; according to which, a flux rope is first developed within the anemone-type active region via the tether-cutting magnetic reconnection. Activation of the flux rope triggers null point reconnection leading to the triggering of the flux rope, a process resembling the coronal breakout at low coronal heights. As a result, we observe the onset of parallel and circular ribbon brightenings sequentially. Our multi-wavelength analysis on circular ribbon flares, complemented by NLFFF extrapolation and associated numerical techniques have provided interesting and important results in this regard. Our studies have revealed that circular flare ribbons can also initiate with the reconnection at the null point, caused by other external factors, that leads to the triggering of the flux rope; resulting in the onset of the circular ribbon brightening prior to the onset of the parallel ribbons. Our analysis has further provided evidence that circular ribbon flares can occur within active regions lacking null points, which can be justifiably considered as a revolutionary idea. In this talk, I will explain the results of our studies on circular ribbon flares and discuss how our new works contribute toward understanding the 3D magnetic reconnection and its role in governing the complex evolution of circular ribbon flares.

Geology of the Crüger-Sirsalis Basin: Evidence of prolonged mare volcanism in the southwestern near side of the Moon

Date: 2021-05-28
Speaker: Ms. Tanu Singh
Venue: Google meet

Abstract

Impact basins on the Moon aid in understanding the stratigraphic evolution of the lunar crust. Several degraded/buried basins on the Moon have been revealed using the Gravity Recovery and Interior Laboratory (GRAIL) data. The Pre-Nectarian aged Crüger-Sirsalis Basin ~ 475 km in diameter and centered at -16.0° N, 293.0° E is one among them. The geology of this basin is largely unknown because it is largely buried under the ejecta of the Orientale, Grimaldi, and Humorum basins. In this study, we have attempted to unravel the geology of the Crüger-Sirsalis Basin using remote sensing datasets primarily acquired from Chandrayaan-1 and Lunar Reconnaissance Orbiter (LRO) missions. We report the probable presence of an inner depression ring (IDR) of diameter ~243 km for the first time, in addition to the inner ring (IR, diameter ~425 km), and outer ring (OR, diameter ~475 km). We report two new floor fractured craters and a new concentric crater, suggesting the presence of shallow magmatic plutons in these regions. A new pyroclastic deposit has been identified along the outer ring of the basin. The spectral study shows that the basin encompasses two types of cryptomare. These two cryptomare units are compositionally distinct. The signatures of pure anorthosite (PAN) and olivine have been found in the craters located along the rings of the basin. This result supports the lunar magma ocean hypothesis. Crater chronology has revealed that the basin has experienced late phase mare volcanism (2.0- 1.4 Ga). Synthesizing the findings from this study and the earlier studies, a detailed geological map of the Crüger-Sirsalis Basin has been prepared for the first time.

The dust cycle in the Martian Atmosphere

Date: 2021-05-21
Speaker: Varun Sheel
Venue: Google meet

Abstract

The presence of dust suspended in the atmosphere, and its temporal and spatial variability are important components of the Martian climate system. Observations and numerical modeling are both critically important for understanding the Martian dust cycle. The talk shall review our current understanding of some aspects of the dust cycle.

Evolution of the complex magnetic structures in AR 12734 using Hall magnetohydrodynamics

Date: 2021-05-20
Speaker: Ms. Kamlesh Bora, SRF, USO/PRL
Venue: Online

Abstract

Hall Magnetohydrodynamics (HMHD) is well known to support faster magnetic reconnection and magnetic field lines (MFLs) evolution having richer complexity compared to its MHD counterpart. In this work, for the first time, we compare data-constrained HMHD and MHD evolution of a solar active region (AR) to explore magnetic reconnections (MRs) triggering a flare by employing numerical simulations augmented with relevant multiwavelength observations. The coronal magnetic field is constructed by employing non-force-free-field (NFFF) extrapolation on the photospheric vector magnetogram.The particular AR under consideration is the AR 12734 during the C1.3 flare on 2019 March 8 around 03:18 UT, followed by a coronal mass ejection (CME). Magnetic structures involved in the flare are identified to be a fluxrope with its overlying MFLs along with a three-dimensional null. Also, the evolution of highly twisted MFLs located beneath its fan and at the middle of a W-shaped flare ribbon are found to be important. Contrary to the MHD simulation, the HMHD simulation shows a higher and faster ascend of the rope along with the overlying MFLs which, further reconnect at a Quasi-separatrix Layer (QSL) located higher up in the corona. The footpoints of the MFLs match better in the HMHD with the central part of a W-shaped flare ribbon visualised on the chromosphere. Additionally, MFLs are found to rotatein a circular pattern in the HMHD whereas no such rotation is seen in the MHD simulation. Interestingly, plasma is observed to be rotating in a collocated chromospheric region which, adds more credibility to the HMHD simulation. Overall, the HMHD simulations are found to agree better with observations and opens up a new avenue to be explored.

On the role of null points and quasi-separatrix layers in magnetic reconnection

Date: 2021-05-13
Speaker: Ms. Sushree Sangeeta Nayak, SRF, USO/PRL
Venue: Online

Abstract

Potential sites of reconnection like null points (where |B|=0) and quasi-separatrix layers (QSLs; regions with sharp change in magnetic field line connectivity) play a major role at the onset of magnetic reconnection and drive the solar transients. However, their simultaneous presence in multiple flux systems makes the process more intriguing to understand the magnetic reconnection in three-dimension. In this direction, the talk will present the results of a set of MHD simulations initiated with both data and analytical boundaries to investigate the impact of null points and QSLs on reconnection in a complex magnetic topological system. _______________________________

Responses of dust loading on the ozone and ionosphere of Mars

Date: 2021-05-07
Speaker: Ms. Siddhi Shah
Venue: Google meet (meet.google.com/cvp-xjyr-fvz)

Abstract

Several dust storms have been observed on Mars. Some storms affect a small region of the planet while other storms can cover the entire planet. The observations were carried out over the last 2-3 Martian decades between MY10 and MY34. We have used SPICAM observations for four Martian Years (MY27-MY30) to study the seasonal variability of column abundances of ozone and dust opacity at low latitudes, mid-latitudes and high latitudes. The observed column abundances of ozone are compared with the MCD model between MY27 and MY30 at these latitudes. In these observations, year-to-year seasonal variability of column ozone were nearly the same except in MY28 at latitude range ~ 10-30oS and Ls~280o-310o when a global dust storm occurred. The altitude profiles of ozone heating rates are also calculated in the presence of a dust storm. It is found that the density of ozone and its heating rates are affected by the global dust storm.

Synthesis of chemical provinces on Mars with the latest geochemical maps

Date: 2021-04-30
Speaker: Ms. Alka Rani
Venue: Google meet (meet.google.com/aob-sate-vjb)

Abstract

Martian chemical provinces defined a decade ago clarified diverse regional processes, including aqueous alteration, the evolution of volcanic provinces and the provenance of sedimentary units. However, the consistency of those chemical provinces with the latest data remains unknown, along with associated geologic processes. Here, I present a geochemical synthesis using a trilogy of multivariate analytical methods to derive a first-order inter-methodologically consistent chemically distinct provinces of the Martian crust. The geochemical mapping and establishing stratigraphic age relationships among the geochemical provinces provide an overview of geological processes operating on Mars and how they have varied in time and space. In that context, I’d present two nearby geochemical provinces (Lunae Planum (LP) and Acidalia Planitia (AP)), to gauge the variations in melt generation at the respective mantle sources and to consider the relative roles of igneous versus aqueous environments in a significant transition zone from highlands to lowlands of Mars.

Impact craters and fluvial processes on Mars

Date: 2021-04-23
Speaker: Dr. S. Vijayan
Venue: Google meet

Abstract

The surface of Mars hosts abundant evidence for impact craters. Mars also has compelling evidence of past and sustained fluvial activity which are widely distributed. These two major geomorphic processes played a significant role in altering/shaping the crust of Mars. The interaction of fluvial activity with the impacts is one of the fundamental quests in the Martian landscape. Several craters on Mars are associated with channels, which act as an inlet or outlet channels. These associated channels will play a major role in inter/intra crater fluvial activities. The associated channels with the crater will also act as one of the potential pathways for water to get into the craters. However, the source for the channel, period/extent of flow, their regional/unique presence brings the need for their detailed exploration. The presence of fluvial landforms within the craters are direct evidence for the record of climatic environments prevailed during the past. However, most of the craters with fluvial records are modified extensively and this post a challenge in understanding them. In this talk, I will discuss such channel associated craters and also why such craters are the highly preferred locations on Mars for landing.

Geology of Scaliger crater region on the Moon

Date: 2021-04-16
Speaker: Neha Panwar
Venue: Google meet

Abstract

Understanding the magmatic processes on the Moon help to decipher its thermal history. Magmatism on the near side can be seen in the form of the mare deposits; however, on the far- side the basalts are present in isolated pockets only and the extent and nature of magmatism is not clearly known. The Scaliger Crater, centered at 27.1°S, 108.9°E is an ~80 km wide crater located at the rim of the Milne Basin in the Eastern Hemisphere of the Moon. This region is situated close to Mare Australe, a mare that lies partly on the near-side and partly on the far-side. Crypromare is present in this area, indicating that the region has experienced magmatism in its geological past. The present study aims to understand the geology of the Scaliger Crater region and its influence on magmatism in an attempt to further the understanding of the magmatic processes on the lunar far-side.

Thermophysical behaviour of the Moon - Agreements and Arguments

Date: 2021-04-09
Speaker: Dr. Karanam Durga Prasad
Venue: Google meet

Abstract

Understanding the global thermophysical behaviour of the Moon is important for both science as well as exploration aspects. Thermophysical measurements on the Moon have also gained importance in light of recent results from various instruments onboard lunar missions. It is well known that the surface temperatures of the Moon are dictated only by the incident solar heat flux, while the subsurface temperatures vary as a function of a number of parameters viz. latitude, dust cover, density/porosity, morphology, composition. Even after numerous efforts carried out for several decades, a comprehensive understanding is still lacking. Present status and anticipated efforts for systematic understanding of global thermophysical behaviour of the Moon will be discussed.

1. Revisiting LPSC 2021 Abstracts; 2. Theoretical estimates of Chromium K-alpha line X-ray signal from moon for mare basalt and anorthositic compositions

Date: 2021-03-26
Speaker: Prof. Debabrata Banerjee
Venue: Google meet

Abstract

Mineralogy, Petrology and Geochemical studies of recently fall Mahadeva Meteorite

Date: 2021-03-19
Speaker: Dr. Dipak Kumar Panda
Venue: Google meet

Abstract

A single piece of meteorite (~15 kg) fell in Mahadeva village of Madhubani district in the state of Bihar in India on July 22, 2019. Based on petrochemical studies, Mahadeva is classified as H-chondrite. Homogeneous olivine (Fa:19.3 mol%) (percent mean deviation <4%) and low-Ca pyroxene (Fs:17.6 mol%) composition further suggest that Mahadeva is highly equilibrated chondrite (resembles petrologic type 5/6), a few relict chondrules still can be recognized. The temperature of equilibration is estimated ~800 °C. Bulk chemical composition is also consistent with the mean H-chondrite.

Flavor specific neutrino self-interaction: $H_0$ Tension and IceCube

Date: 2021-03-18
Speaker: Priyank Parashari
Venue: Online

Abstract

Over the past few decades, the huge influx of data from cosmological and particle physics observations have enabled us to understand and test the viability of the theories. However, these observations have also yielded some discrepancies which hint towards the new physics. One such discrepancy is the mismatch between the value of the Hubble constant ($H_0$) obtained from the direct local measurements and that inferred from the Planck CMB observation within $\Lambda$CDM cosmology. This is known as the $H_0$ tension. Self-interaction between active neutrinos had been proposed as a solution to the $H_0$ tension. Similar self-interaction can also explain the observed dips in the flux of the neutrinos in IceCube detectors. In this talk, I will explain the $H_0$ tension and observed dips in IceCUbe as a signature of flavor specific self-interaction between active neutrinos.

The origin of Insoluble organic matter in meteorites: A Multi-technique study

Date: 2021-03-12
Speaker: Shreeya Natrajan
Venue: Google meet

Abstract

Meteorites, mostly of the chondritic types contain up to 5wt% of carbon in both organic and inorganic forms. The acid insoluble fraction of this is a kerogen type material known as the insoluble organic matter (IOM), The origin of IOM is a widely debated subject. Studies have speculated that there are two possible origins of IOM, one from the cold depths of the Interstellar medium (extremely low temperature environments 10-30K) or from the outer solar nebula (beyond 40 AU). To look at these we have chemically separated IOM from various meteorites and studied their characteristics. These organic constituents are a tell-tale of their journey through the interstellar space beginning with low temperature radiation-driven chemistry and isotopic fractionation in a molecular cloud at the beginning of solar system formation. They were incorporated into planetesimals like asteroids and comets where further reactions and processing took place as these objects grew and experienced post-accretion alterations. Processes such as impact shock, radiogenic decay of short-lived radionuclides (e.g., 60Fe and 26Al) heated the planetesimals, thereby forming a long and diverse range of thermal metamorphism and aqueous alteration conditions which in turn affect the formation, destruction and transformation of the organic content within. Therefore, understanding these alteration conditions is the first step towards delineating the origin of IOM.

Yu-Shiba-Rusinov states of single magnetic molecule in an s−wave superconductor

Date: 2021-03-11
Speaker: Saurabh Pradhan
Venue: Online

Abstract

We use the numerical renormalization group theory to investigate the Yu-Shiba-Rusinov (YSR) bound state properties of single magnetic molecules placed in an s-wave superconducting substrate. The molecule consists of a large core spin and a single orbital, coupled via exchange interaction. The critical Coulomb interaction for the singlet/doublet transition decreases in the presence of this exchange interaction for both Ferro and anti-ferromagnetic couplings.The number of YSR states also increases to two pairs, however, in the singlet phase, one of the pairs has zero spectral weight. We explore the evolution of the in-gap states using the Anderson model. Away from the particle-hole symmetry point, the results suggest a doublet-singlet-doublet transition as the on-site energy is lowered while keeping the Coulomb interaction fixed. To understand these results, we write down an effective model for the molecule in the limit of a large superconducting order parameter. Qualitatively, it explains the various phase transitions and spectral nature of the in-gap states.

Atmospheric Escape from Mars

Date: 2021-03-05
Speaker: Prof. S. A. Haider
Venue: Google meet

Abstract

Atmospheric loss has been a primary driver of climate evolution over Martian history. One major loss process is photochemical transport escape, whereby dissociative reactions in the Martian upper ionosphere provide sufficient energy for atomic products of the reaction to escape Mars’ gravity. O2+, NO+, CO2+, O+, N+, C+, and H+ have been escaping from Mars in this manner over Martian history, their escape rates depending on solar EUV (which was much higher in the past) and the composition of the atmosphere near the exobase. While escaping these ions cannot be directly detected, the MAVEN orbiter measures all necessary quantities in situ, when combined with appropriate modeling of hot atom/ion transport allow photochemical escape rates to be calculated. Using kinetic transport model, we have calculated escape flux and escape rates of O+, O2+, NO+ and CO2+ at exospheric plasma temperatures 1000 K, 1500 K and 2000 K in the exosphere of Mars between 200 km and 8000 km. These calculations are carried out in the mini-magnetosphere of Mars. We report maximum escape rate of the order 1e23-1e24 s-1 for O+ implying the loss of 8-300 mbar of oxygen over 4Ga. These results are in good agreement with MAVEN observations. In this lecture, we will present updated estimates of escape flux and density of these ions with understanding of all atmospheric loss processes at Mars and their effects on Martian climate over solar system history.

Al-Mg systematics in Itokawa silicate grains from sample return mission, Hayabusa-1

Date: 2021-02-19
Speaker: Prof. Kuljeet Kaur Marhas
Venue: Google meet (https://meet.google.com/vhs-vqny-gca)

Abstract

26Al-26Mg systematic is a relative chronometer used for delineating various events taking place within the first few million years of formation of the Solar system. Asteroids are the remanants of the planetesimal building process that failed to accrete to larger bodies or formed due to impact collision between larger planetesimals. Al-Mg analyses on particles found on Itokawa asteroid help to compare the timescale of their formation (last resetting event) relative to Calcium Aluminium Inclusions (CAIs), the first forming solids in the Solar System. Asteroid Itokawa is thought to be the parent body of LL4-6 ordinary chondrites, which indicates that the asteroid has experienced extensive thermal alteration processing. Metamorphic grade of LL4-6 means that the object might have seen a temperature of around 600-700 degree Celsius. According to previous Al-Mg studies in unequilibrated ordinary chondrites of higher metamorphic grade, disturbance/absence of 26Al records has been observed and has been attributed to thermal metamorphism. The timescales of Itokawa grain formation have been estimated using nanoSIMS. And a discussion on thermal metamorphism along with an extended duration of grain formation (like chondrule) or large scale heterogeneity in 26Al might is being debated.

‘Planetary Sampling Technology’: A system development, project perspective

Date: 2021-02-12
Speaker: Mr. Nirbhay Kumar Upadhyay
Venue: Google meet (https://meet.google.com/vhs-vqny-gca)

Abstract

There are obviously important advantages of collecting samples on planetary bodies and bringing them to Earth for study. One among many is the ability to look at ever-smaller pieces/aspects of samples, as instrumental sensitivities continue to improve. Researchers’ capacity to analyze very small subsamples also means that a returned sample of modest size can be divided and studied by a large number of scientists in laboratories with diverse capabilities. Having samples present on Earth allows investigators to develop and to answer refined, second-order questions. It also makes it possible for observations of particular importance to be checked by multiple investigators using the same or different techniques. Realizing the need of futuristic course of space exploration by Indians, our team at Planetary Sciences Division has been working on planetary sample return mission aspects. A proposal of “Planetary sampling through automated core drilling” was submitted to Directorate of Technology Development and Innovation (DTDI), ISRO HQ. Resulting in proposal acceptance, an advanced R&D futuristic project named as “Planetary Rock Sampling Technology” is formulated by ISRO HQ, which will aim for automated core drilling of planetary sub-surfaces for future sample return missions. This will ensure technological readiness for planetary geology missions of ISRO. In this seminar an overview of the project and the system development aspects involved in the project realization, shall be presented.

Modeling of CO Cameron band dayglow emission on Mars

Date: 2021-02-05
Speaker: Masoom P. Jethwa
Venue: Google meet (https://meet.google.com/vhs-vqny-gca)

Abstract

Dayglow is an aeronomical process of the dayside atmosphere occurring due to the interaction of solar radiation with atmospheric gases. Dayglow helps us in understanding the structure of atmosphere, excitation processes, and lifetimes of excited species. The CO Cameron band (180 – 260 nm) arises due to the transition from the excited a3pi state to the ground X1Σ+ state of Carbon Monoxide. In this seminar, the excitation mechanisms, modelled emission rates and intensities of CO Cameron band will be presented. Comparison of our modelled results with SPICAM and IUVS datasets onboard Mars Express and MAVEN will also be discussed.

Boom deployment mechanism of Langmuir Probe and Electric Field Experiment (LPEX) Payload onboard MOM-2

Date: 2021-01-29
Speaker: Janmejay Kumar
Venue: Google meet (https://meet.google.com/vhs-vqny-gca)

Abstract

Langmuir probe and electric field experiment (LPEX) is a selected experiment for India’s Mars Mission-2. It is a payload which measures the electron density and electrostatic field in Martian ionosphere. In this payload, a boom is required for proper operation of the payload. For stowing and deploying the long boom a deployment mechanism is required. The preliminary configuration design of deployment mechanism has been completed. Deployment mechanism is integrated by torsion spring, boom, latching system, HDRM and Micro switch. In this mechanism 1 meter CFRP boom with probe at other end will be deployed into Mars orbit. Deployment is accomplished by releasing the strain energy stored by torsion spring. In this seminar I will discuss about mechanical system of deployment mechanism and its function. I will discuss about boom design, static analysis and Modal analysis (Theoretical as well as FEA (COMSOL) analysis) in stowed state and deployed state and finally I will show the 3D printed prototype of boom deployment mechanism.

Infilled craters in the mare regions of the Moon

Date: 2021-01-22
Speaker: Kimi Khungree Basumatary
Venue: Google meet (https://meet.google.com/vhs-vqny-gca)

Abstract

Impact craters are the predominant features on the Mare and Highland regions of the Moon. The Moon has recorded more than one million impact craters of different diameters. The Mare region is known for its lava deposits, which covers ~17% of the moon surface. Interestingly, many craters within this Mare region hosts lava deposits within their floor, which indicates the post-impact modifications. Impact craters that are filled with lava, in general, appear as a nearly flat floor in the visible imagery, referred here as Infilled craters. The fractures formed beneath the crater floor during the impact event act as a pathway for these lava to intrude into the crater. This intrusion differs with crater diameter, the spatial location of Mare region, and with geological age of adjoining lava/surface. Due to the lack of plate tectonics and atmosphere Moon provides us with the desired setting to study such infilled craters, which are the record holders of the past geological activities. A detailed study of Infilled craters on the Moon is indeed important for the understanding of lava activities underwent on the Moon. In this current work, detailed scrutiny of infilled craters will be carried out over different Mare regions. This study will lead to understand: 1) the spatial distribution of infilled craters in the mare regions of the Moon, 2) the period of lava infilling activities underwent, and 3) the source of the lava and its variations. In the talk, I will discuss the different types of infilled craters identified in the mare regions, few observations from those craters, and the implications of this study.

Gully fan formation processes: New insights from morphometric measurements

Date: 2021-01-15
Speaker: Rishitosh Kumar Sinha
Venue: Google meet (https://meet.google.com/vhs-vqny-gca)

Abstract

Martian gullies are linear-to-sinuous channels linking an alcove at the top to a fan at the bottom. The gullies are interesting because they resemble gullies found on Earth carved by fluvial processes and that’s the reason their genesis is linked to possible episodes of past (scanty) flow of water on Mars. However, from the previous studies and our latest (Sinha et al., 2020) high-resolution global investigation of Martian gullies, we have noted that their mode of formation is controversial. This is because (1) the climate of Mars during the late Amazonian epochs (<100 Ma) is not believed to be conducive to the production and flow of liquid water – disagreement to the fluvial process, (2) the present-day activity in gullies may be driven by sublimation of seasonal carbon dioxide frost – favoring the dry process, and (3) the evidence of overlapping lobate deposits in gullies suggests possibility of a debris-flow like process (Sinha et al., 2020). Furthermore, the gully fans are often modified by post-depositional processes such as by draping of ice-dust mixture and aeolian processes – leading to concealment of key signatures vital for the interpretation of gully fan forming processes. In this work, we carry out morphometric measurements of the gully fans characterized by distinct morphologies using all the publicly available digital elevation models of gully fans within 30-75 deg. of the northern and southern hemispheres. The purpose of this global investigation is to quantitatively characterize a large variety of gully fans to conscientiously identify the attributes of the gully fan shape diagnostic of the gully fan formation processes. We believe that this work will eventually be an important step towards advancing our understanding of the role of past flow of ice and water in shaping the Martian surface.

Detection of lightning in Planetary Atmosphere

Date: 2021-01-08
Speaker: Dr. Y.B. Acharya
Venue: Google meet (https://meet.google.com/vhs-vqny-gca)

Abstract

Lightning in planetary atmospheres is now a well-established concept. Planetary lightning detection technology has developed considerably since the first observations at Jupiter in the late 1970s. Space instruments for lightning detection have focused on radio and optical detection techniques. Here we discuss the available detection techniques for the observations of planetary (including earth) lightning by spacecraft. Space missions carrying lightning-related instrumentation will also be discussed.

Radar exploration of the Moon: Scientific potentials of Chandrayaan-2 DFSAR

Date: 2021-01-01
Speaker: Dr. Sriram S. Bhiravarasu
Venue: https://meet.google.com/vhs-vqny-gca

Abstract

Radar exploration of the Moon has started since the early 60's from ground-based radar telescopes that resulted in a vast majority of new information about the nearside of our Moon. This was followed by a couple of spacecraft-based radar instruments for the Moon in the last decade, which have provided some significant results about its physical properties. Some of these include about the subsurface structure of the mare, volcanic deposits, crypto mare and polar volatiles. In this talk, I will briefly concentrate on some of these prior results followed by a discussion on where the Ch-2 DFSAR instrument could fill the gaps and provide new insights into our current understanding. The speaker: Dr. Sriram Saran Bhiravarasu received the M.Sc. degree in Physics from Nagarjuna University, Andhra Pradesh, in 2006 and M.Tech. degree in Geomatics from Jawaharlal Nehru Technological University (JNTU), Hyderabad in 2008. He received his Ph.D. degree in Physics from Gujarat University in 2016. From 2010 to 2017, he worked as a Junior Research Fellow and a Research Associate at Space Applications Centre (ISRO), Ahmedabad, where he was involved in the polarimetric radar studies of the Moon using orbit-based radar data sets. From 2017 to 2018, he worked as a Postdoctoral Research Scientist with the Planetary Radar Group at the Arecibo Observatory, Puerto Rico, where he was involved in the radar observations of Near Earth Asteroids (NEAs), Comets, and the Moon. From 2018 to 2020, he was a Postdoctoral Fellow with the Lunar and Planetary Institute (LPI), Houston, where he was involved in the polarimetric radar studies of the Terrestrial Planets and Asteroids, along with laboratory simulation studies to investigate planetary radar scattering processes. Currently, he is back with the Space Applications Centre (ISRO), Ahmedabad as a Staff Scientist in the Planetary Science Group, working on the Chandrayaan-2 mission.

2020

The beginning of the SKA era : Exciting initial results from the South African SKA pathfinder MeerKAT

Date: 2020-12-24
Speaker: Dr. Viral Parekh (Rhodes University South Africa)
Venue: https://meet.google.com/aev-fbgt-xdk

Abstract

MeerKAT is the South African radio astronomy project developing in the direction of building the ambitious Square Kilometer Array (SKA) radio interferometer. MeerKAT array consists of 64 dishes is located in the Karoo desert, north of the South Africa. MeerKAT is now fully operational and already started to deliver remarkable results both in continuum and spectral line observations at GHz frequencies. In this talk, I will show the initial continuum science results from the MeerKAT high sensitive radio observations. I will also talk about our ongoing galaxy cluster science projects with MeerKAT.

Radio diagnostics of impulsive events on the Sun

Date: 2020-12-22
Speaker: Ms. Sherry Chhabra, New Jersey Institute of Technology & NASA Goddard Space Flight Center, USA
Venue: Online

Abstract

Radio diagnostics hold great importance in exploring strong, impulsive bursts, consequently characterizing the space environment at the Sun, near Earth, and elsewhere in the solar system. In recent years, new instruments have come online that can be used for imaging spectroscopy of the Sun at high temporal, spectral, and spatial resolution. This talk reviews the radio emission that is observed from the Sun during impulsive bursts. Using the data obtained from different radio instruments such as Expanded Owens Valley Solar Array (EOVSA) and Very Large Array (VLA), I will go over a few cases of radio emission at high frequencies and the diagnostics they provide. At lower frequencies, I will discuss in detail, a CME-Associated solar radio event observed by the new instrument Owen Valley Radio Observatory - Long Wavelength Array (OVRO-LWA).

Front-End Electronics design for the Venus Radiation Environment Monitor (VeRad) payload

Date: 2020-12-18
Speaker: Deepak Kumar Painkra
Venue: Google meet (https://meet.google.com/vhs-vqny-gca)

Abstract

Venus Radiation Environment Monitor (VeRad) is a shortlisted payload for the Venus orbiter mission. It aims to measure the high energy solar particles entering the Venus atmosphere in the energy range of 100keV to 100MeV. VeRad consists of a stack of SiPIN and scintillator detectors. Each detector is readout by an independent chain of electronics. Scintillator detectors are readout with the help of silicon photomultipliers (SiPM). SiPMs consists of an array of small size microcells (photodiodes) operated in Geiger mode. In this talk, I will discuss the design aspect of Front-End Electronics (FEE) for these detectors. This basically involves acquiring the charge generated in the detectors and then shaping them into pulse signals without adding extra noise into it.

Charge dissipation in Dark regions

Date: 2020-12-11
Speaker: Dr. Sanjay Kumar Mishra
Venue: Google meet (https://meet.google.com/vhs-vqny-gca)

Abstract

We address a fundamental issue of the development of steady-state electric potential in the electron-rich region within the permanently shadowed craters on Moon. The surface continuously interacts and collect the high energy electrons, causing the growth of negative charge indefinitely under the notion of insignificant neutralizing current – this is physically inappropriate, and the current balance on the crater surface has been an open question since long. As a novel solution to this, we propose that the charged dust grains lying on the crater surface can be efficient field emission sources that can generate sufficient neutralizing current causing steady-state surface potential. Even a marginal dust cover is sufficient to establish the steady-state, and the crater surface may acquire finite potential. The concept also suggests a remedy to avoid excessive electrical charging of objects during Moon exploration. All these aspects will be briefly discussed in this conversation.

Nitrogen isotopes in chondrules and metal separates from ordinary chondrites

Date: 2020-11-27
Speaker: Ramakant R. Mahajan
Venue: Google meet (https://meet.google.com/vhs-vqny-gca)

Abstract

Understanding the formation of our planetary system requires identification of the materials from which it originated and the accretion processes that produced the planets. The compositional evolution of the solar system can be constrained by synthesizing datasets with elemental and isotopic compositions from objects that directly sampled the disk, e.g. meteorites and their constituents (chondrules, refractory inclusions, metal, and matrix). Nitrogen is one of the major element present in the proto-planetary disk. The isotopic ratio of nitrogen, 14N/15N, in various objects of the Solar System (meteorites, comets, planets, etc.) shows the largest variations among the most abundant constituents. The isotopic ratio of nitrogen measured in primitive Solar System bodies shows a broad range of values, the origin of which remains unknown. The primordial nitrogen reservoirs in the solar system with distinct 14N/15N ratios which are the building blocks of the bodies in solar system. The key question is whether these isotopic reservoirs of nitrogen predate the formation stage or are posterior to it. Another central question is elucidating the processes that can produce the observed variations in the 14N/15N isotopic ratio. When, where, and how these isotopic reservoirs of nitrogen formed during the evolution from a molecular cloud to planetary systems remains to be determined. In this talk, N isotopic ratios in meteoritic constituents will be discussed.

The Space weathering trends at lunar Swirls

Date: 2020-11-20
Speaker: Dr. Megha Bhatt
Venue: Google meet (https://meet.google.com/vhs-vqny-gca)

Abstract

Swirls are the features only found on the lunar surface which are identified by complex loops of ribbons of bright albedo associated with magnetic anomaly regions. These features are of specific interest because their origin and their spectral characteristics are not fully understood. The higher albedo of the swirls compared to their surroundings is generally explained due to magnetic shielding of the surface from the solar wind. Another plausible formation mechanism proposed is resurfacing due to one or multiple cometary impacts. The spectral characteristics of swirls have been extensively studied in UV-VIS-NIR wavelength region. I will talk on the infrared properties of the swirls and present a case study considering process of surface interaction with cometary material which can remove the uppermost layer of mature material and can play a role in the formation of the swirls.

How Magmatism Help Understanding Planetary Evolution? Mars: A Case Study

Date: 2020-11-13
Speaker: Dr. Amit Basu Sarbadhikari
Venue: Google meet (https://meet.google.com/vhs-vqny-gca)

Abstract

Magmatism plays an important role in understanding the formation and evolution of the terrestrial planets. We need to understand the chemical composition of solidified magma that helps us to decode the planetary evolution. The magmatic as well as thermal evolution of a terrestrial planet has a significant impact on the planet’s tectonic, magnetic, and geologic history. In this talk, I’ll present a holistic view of different aspects of magmatism (and volcanism). Then, in order to understand the observed processes and features, those which influence the thermal and chemical evolution of terrestrial bodies, I’ll discuss about the integrated evidences from various fields of science into consistent models. Finally, I’ll showcase Mars for an application of this approach.

Martian upper atmosphere : CO+ First-negative band emission is a tracer of Carbon Monoxide

Date: 2020-11-06
Speaker: Dr. Susarla Raghuram
Venue: Google meet (https://meet.google.com/vhs-vqny-gca)

Abstract

Martian thermosphere is strongly influenced by the lower atmosphere and its composition is essentially driven by both solar radiation and solar wind. Photon driven neutral chemistry plays an important role in determining the stability of CO2 in the Martian atmosphere. In this webinar, I will talk on the modelling studies of CO+ first-negative band emission in the Martian upper atmosphere and discuss their implications. Our modelling work suggests that this band emission can be used as a tracer to study the day side distribution of CO, which is important to study the stability of CO2, in the Martian upper atmosphere.

HI absorption associated with a quasar at z~3.5

Date: 2020-11-05
Speaker: Dr. J.N.H.S. Aditya (PRL Ahmedabad)
Venue: https://meet.google.com/aod-mbxm-vmz

Abstract

Studies of HI 21-cm absorption associated with AGNs have been finding a dearth of absorbers in high redshift (z > 1) samples, while there are over 150 such detections in systems at low redshifts. A low HI 21-cm absorption strength is reported in a large and uniformly selected sample of high redshift flat-spectrum sources, which has been attributed to either a redshift evolution in gas properties, or to a high AGN UV and/or radio luminosities. A cut-off UV luminosity (10^23 W/Hz) has been proposed in the literature, above which all the neutral hydrogen in a typical Milky-Way like host galaxy is expected to be completely ionised. In our recent work, we report HI 21-cm absorption, and Lyman-alpha absorption, associated with the high redshift (z~3.5) flat-spectrum radio source 8C 0604+728. The UV luminosity of the source exceeds the above-mentioned cut-off. The detection of neutral gas associated with the AGN provides evidence contrary to the literature hypothesis. In this talk, we discuss the implications of these results.

SHARAD detections of subsurface deposits near Mangala Fossa, Mars

Date: 2020-10-23
Speaker: Rajiv Ranjan Bharti
Venue: Google meet (https://meet.google.com/vhs-vqny-gca)

Abstract

We present the first Shallow Radar (SHARAD) based observations of subsurface reflections near the Mangala Fossa region, immediately adjacent to the fossa at 19.2° S, 151.2° W and within an unnamed crater at 21.0° S, 150.5° W. Our analysis of radar propagation at these sites reveals a low dielectric subsurface material (average dielectric constant ≤ 6) that is unexpected in this region. Lava flows dominate the surface, so the low dielectric is notably different from SHARAD investigations of lava flows in the adjacent Tharsis region. The subsurface reflector trail is not visible on the surface, so a wave propagation model is used to derive the dielectric constant. Here, I will talk about the model setup, the reflector hypothesis, and its origin.

Intra-night optical variability (INOV) in radio-loud narrow line Seyfert 1 (RL-NLS1) galaxies

Date: 2020-10-22
Speaker: Dr. Parveen Kumar (PRL Ahmedabad)
Venue: https://meet.google.com/iap-bdrh-oug

Abstract

Narrow-line Seyfert 1 galaxies (NLS1s) are active galactic nuclei (AGN) possessing systematically lower black hole masses. Several radio-loud NLS1s (RL-NLS1s) have been detected in gamma-ray energy bands suggesting the presence of blazar-like jets in RL-NLS1s. Relativistic-jets in RL-NLS1s are further confirmed from the high-resolution very large baseline array (VLBA) observations. Therefore, RL-NLS1s present a challenge for the relativistic jet paradigm, which states that powerful radio jets are associated exclusively with very high SMBHs. Given the limitations of radio and γ-ray observations, optical monitoring can be used as a complementary tool to infer the presence of relativistic jets in RL-NLS1s. AGN with relativistic jets aligned close to the line-of-sight are expected to exhibit INOV due to the beaming effect. To probe INOV in RL-NLS1s, we have carried out optical monitoring of a sample of RL-NLS1s. In this talk I shall present statistical results of INOV in NLS1s and their plausible interpretation.

Lunar Escape Process

Date: 2020-10-16
Speaker: Dr. Jayesh P. Pabari
Venue: Google meet (https://meet.google.com/vhs-vqny-gca)

Abstract

Dust particles exist everywhere in interplanetary space and they evolve dynamically after their origination from the sources like Asteroid belt, Kuiper belt, comets or space debris left during the formation of solar system. These micrometeorites encounter the inner planets, while they spiral-in towards Sun. From whichever come to Earth, many particles are ablated in the Earth’s atmosphere and leave metallic ions behind. In case of Moon, all such particles can reach the surface without ablation owing to the absence of atmosphere. Due to the impact of hypervelocity dust particles on lunar surface, ejecta come out in the lunar environment. In some cases, the ejecta velocity could be larger than the escape velocity and particles may be able to escape from Moon. Further, the escaping ejecta may carry water ice (volatiles), whenever incoming projectiles hit the surface in polar region with the water ice present. Using Galileo observations of the dust particles near Moon, the ejecta parameters are computed and the possible escape of volatiles from Moon is estimated. Considering the incident angle distribution, the upper limit of regolith escape rate is found to be ~2.218 × 10-4 [1.662 × 10-4, 10.232 × 10-4 ] kg/s. Similarly, the upper limit of water ice escape rate is found to be ~1.988 × 10-7 [1.562 × 10-7, 7.567 × 10-7 ] kg/s. On one side, Moon is found to be gradually becoming heavier due to its one order higher incoming dust particles than those escaping from it. While on the other side, Moon could be depleted of water ice (volatiles) resources over a period of time, because of the escape due to micrometeorite impact. The escape process on Moon is established, which will be presented in seminar, along with the results to understand dust and volatile escape from Moon.

Understanding and Quantifying the Biological Carbon Pump in the Indian Ocean using naturally occurring radionuclides in seawater as tracers

Date: 2020-10-13
Speaker: Dr. Subha Anand S.
Venue: Online Platform (Google Meet )

Abstract

Ocean acts as a significant reservoir of carbon on the earth’s surface. Tiny photosynthetic organisms, the phytoplankton, present in the sun-lit layers of the ocean accounts for about 50% of the global net primary production. The process by which phytoplankton photosynthetically fixes atmospheric CO2 and produces particulate organic carbon that sinks from sea surface to bottom and remains stored for longer time scales is termed as the biological carbon pump. The efficiency of the biological carbon pump is determined by the ratio of the amount of organic carbon sinking below the euphotic depth to that produced. This efficiency can be determined by using particle reactive radionuclides present in seawater. Particle reactive radionuclide approach is considered to be more advantageous because of the natural occurrence, specific half-life, continuous decay and secular equilibrium. My research work in the Bay of Bengal, Arabian Sea and the Indian Ocean, focuses on (1) estimating the POC export flux from monthly to seasonal time scales using the particle reactive radionuclide pairs, 234Th/238U and 210Po/210Pb. (2) The role of vertical eddy diffusive mixing in enhancing nutrient concentrations in the surface waters from sub-surface depths using Radium isotopes (228Ra and 226Ra) (3) Quantifying lithogenic inputs to the ocean and palaeo particle flux using 232Th, 230Th and 231Pa isotopes (4) Comparison of measured primary production and estimated POC export flux with that of the globally existing empirical models with an approach to develop a model for the Indian Ocean.

Diversity of minerals in aqueously altered Mukundpura meteorite

Date: 2020-10-09
Speaker: Dr. Dipak Kumar Panda
Venue: Google meet (https://meet.google.com/vhs-vqny-gca)

Abstract

Carbonaceous chondrites are fragments from primitive parent asteroids, which represent some of the most primitive meteorites accessible for laboratory analysis and therefore offers the best opportunity to explore the chemical and physical conditions in the early Solar System. In chondritic meteorite, CM meteorite represents one of most primitive meteorite group and are the fragments of primitive asteroids. CM type is also very important to understand the role of extra-terrestrial water in the solar system. Due to the aqueous alteration, diversity in alteration product is observed in CM type meteorite. Formation of alteration products mainly depends the type of fluid, amount of H2O and duration of interaction between the parent body with the fluid.

Exploring NGC 6300: A Changing-look AGN

Date: 2020-10-08
Speaker: Dr. Arghajit Jana (PRL Ahmedabad)
Venue: https://meet.google.com/iyq-wgwx-ygf

Abstract

Changing-look (CL) AGNs are known to switch between type-1 and type-2 galaxies. In X-rays, the changing-look events are associated with the changes of flux, spectral shape, and line-of-sight hydrogen column density. Change of accretion states, migrating clouds in the line-of-signt, tidal disruption events, supernovae are believed to be the reasons for the CL events. NGC 6300 is a nearby CL AGN. We study the spectral and timing properties of NGC 6300 using Suzaku, Chandra and NuSTAR data, obtained between 2007 and 2016. From our analysis, we find that the circumnuclear tours is clumpy, and migrating clouds are responsible for change in line-of-sight hydrogen column density. Accretion rate is responsible for the spectral variability. We also find that the torus and AGN both evolve simultaneously between 2007 & 2016.

Impact craters role in Planetary evolution

Date: 2020-09-25
Speaker: Dr. S. Vijayan
Venue: Google meet (https://meet.google.com/vhs-vqny-gca)

Abstract

Impact craters are one of the predominant features on most of the planetary/satellite bodies in the Solar System. The crater diameter, depth, post-impact geological processes will differ from one planetary body to another. This can be used to decipher the crustal evolution of that planetary body. Impact craters that form over different geological timescale will act as a chronological record. Based on their formation epoch, the craters preserve or undergo degradation/alteration or post processes. In this talk, I will discuss the impact craters on Mars and how they help in the evolution of the Martian crust. Mostly, this talk will focus on the post-impact conditions and give example how the craters help to understand the fluvial, volcanic, water-ice, and other recent processes within it. Finally, a few examples from other planetary/satellite bodies will be discussed to bring out the role of impacts in planetary/satellite bodies evolution.

Applications of radiogenic and non-traditional stable isotopes to investigate silicate weathering, crustal recycling and mantle geodynamics

Date: 2020-09-22
Speaker: Dr. Anupam Banerjee
Venue: Online Platform (Google Meet )

Abstract

Weathering of silicate rocks releases cations which are transported to the oceans by rivers where calcium carbonate precipitates from the seawater; resulting in the net consumption of atmospheric CO2. These marine carbonates are eventually subducted resulting in mantle heterogeneity, sampled by mantle-derived magmas. Long-lived radiogenic and non-traditional stable isotopes provide insights into both the surface and deep mantle processes. Significant variations in the long-lived radiogenic Nd, Sr and stable Ca isotopic compositions of a 2.5 billion years old weathered basalt suggest that selective weathering of rock forming minerals (plagioclase versus pyroxene) could change the isotopic compositions of silicate rocks in a hand-specimen scale. Such mechanism is likely to be more pronounced in temperate climatic conditions where incongruent weathering is more dominant. This process has important implications for the isotopic variability in global rivers draining through the temperate climate region (e.g., Icelandic rivers). Stable calcium isotope (expressed as 44/40Ca w.r.t NIST SRM 915a) is also a potential tracer of crustal recycling since surface carbonates have much lower 44/40Ca (0.1-0.6‰) than Earth’s mantle (0.94 ± 0.10 ‰). Calcium isotopic compositions of carbonatites, magmatic rocks with more than 50% carbonate minerals, provide insights into the crustal recycling due to its high calcium and carbonate contents. The correlated variation of 44/40Ca with 87Sr/86Sr of global carbonatite samples, of age 2.61 Ga until recent, suggests the presence of recycled carbonates in their mantle source regions. However, a closer inspection reveals that crustal recycling is more prominent in the last 300 million years. The prevalent Ca and Sr isotope signatures observed in carbonatites younger than 300 Ma could reflect the following: (1) an increased amount of subduction flux and high convergence rates due to amalgamation and subsequent break-up of the Pangea supercontinent; (2) enhanced weathering of aragonitic shelf carbonates linked with the Siberian Trap magmatism at ~251.9 Ma.

Terrestrial Impact Structure-Identification and Challenges

Date: 2020-09-18
Speaker: Dr. Dwijesh Ray
Venue: Google meet (https://meet.google.com/sge-jsxb-oek)

Abstract

Impact process is one of the fundamental planetary processes that shape the Solar System bodies. However, the record of impact process on Earth is far from complete (relatively low number of well-preserved impact craters) due to several reasons (e.g. erosion, tectonics, sedimentation and burial). In this talk, I will discuss the challenges to deal with impact structures on Earth especially the identification processes of new impact structures. Older impact structures on Earth are difficult to recognize while younger craters are somehow recognizable. In addition, I will discuss the new results on Ramgarh structure, Rajasthan - India’s third, confirmed impact structure. Finally, I will wind up citing the possible impact structures of Indian subcontinent and future prospects.

Cratons to supracrustal belts: growth and unification of the Indian landmass

Date: 2020-09-15
Speaker: Dr. Sabyasachi Chattopadhyay
Venue: Ground Floor Lecture Hall

Abstract

Archean crustal terranes (4–2.5 Ga) consist of gray-gneisses referred to as the tonalite– trondhjemite–granodiorite (TTG) suite of rocks. These TTGs constitute > 50 % of the existing Archean crust and represent the oldest archetypical juvenile felsic components of cratons and marks the transition from a dominantly mafic to a more felsic crust. There is also considerable debate on the nature of the petrogenetic and geodynamic processes that generated the early continental crust. Whether conventional plate tectonics operated in the Archean, the way it switched over in Proterozoic, and when these came into existence remains unclear. The Singhbhum craton in eastern India is underlain by Paleo - to Mesoarchean TTGs and granites that formed in two pulses at 3.45–3.44 Ga and 3.35–3.32 Ga, followed by potassic granite activity at 3.1 Ga. Low heavy-REE concentrations, Sr/Y and Eu/Gd, and high Nb, Ta, and Y concentrations indicate they belong to the low HREE, medium- to low-pressure TTG type. Their compositions are similar to TTGs derived from chondritic source with amphibolitic residue, consistent with rutile-free and garnet-bearing metabasic source. The younger granites represent intracrustal melts of more potassic members of the Paleoarchean TTGs. The trace element characteristics of the granitoids reflect melt generation at different depths in a tectonic setting producing both TTGs as well as granites contemporaneously. Plausible geodynamic settings could be very hot subduction or “dripduction” regime involving shallow melting of delaminated mafic crust producing the 3.45 Ga juvenile TTGs and minor granites. Large-scale delamination and melting of mafic lower crust and felsic protocrust in a thickened crustal pile in a subduction-like regime could have produced granitoids with juvenile as well as recycled isotopic signatures. The Nd-Hf isotope data indicate that the Paleoarchean upper mantle was moderately depleted in response to a spurt in Paleoarchean continental growth.

Effect of Lunar Landing on its surface, surrounding environment and hardware: A numerical perspective

Date: 2020-09-11
Speaker: Sanjeev Kumar Mishra
Venue: Google meet (https://meet.google.com/vhs-vqny-gca)

Abstract

With renewed interest in lunar exploration, soft landing on the Moon has gained prominence in the recent past. Most of the modern-day landers use thrusters to make a safe and soft landing. However, the jet plume produced by the exhaust of these thrusters creates disturbance on the lunar surface which first leads to surface disturbance and subsequently create damage by the ejected particles to the surroundings and hardware present in the vicinity of the landing site. Understanding this disturbance and assessing the damage is significant both for science as well as mission safety, particularly, keeping in view the plans for ISRU (In-situ Resource Utilisation)/Lunar outpost activities in future. In this talk, I will give an overview of lunar landing and the challenges associated with it and will discuss the work carried out to quantify the regolith damage, ejecta kinematics and damage to pre-existing hardware in the vicinity of landing site.

Processing electronics development for Aditya Solar Wind Particle Experiment(ASPEX) - The process and challenges

Date: 2020-09-04
Speaker: Arpit R. Patel
Venue: Google meet (https://meet.google.com/vhs-vqny-gca)

Abstract

ASPEX, one of the payload for the upcoming Aditya-L1 mission, consist of particle analyzers to carry out systematic and continuous in-situ measurement of solar ions over an energy range spanning 100ev to 20 MeV/n originating from solar wind and coronal mass ejections (CME), arriving at L1. Two different techniques are employed to construct the particle spectrometers which cover the entire energy range. The first one SWIS uses MCP detector to analyze ion energy along with its arrival direction for ion energy range of 100 eV-20 keV. To cover the other end of energy spectrum, another sub-payload named STEPS is employed. STEPS uses solid state detectors to analyze the ions having energy from 20 keV/n to 20 MeV/n. A mechanically common and electrically independent Processing electronics package consisting of FPGA cards, power cards and space craft interfaces serves both SWIS and STEPS. In this talk, I will be discussing about the development process of ASPEX processing electronics package, it’s qualification and challenges faced while development. I will discuss in detail about the flow of development which includes both hardware and software (FPGA code) development. I will also discuss the development of ground checkout system which is also important system for payload testing.

Hydroxyl Radical Generation from Atmospheric Aerosols over a High Altitude Site in the Indo-Gangetic Plain

Date: 2020-08-31
Speaker: Dr. Anil Patel
Venue: Online Platform (Google Meet )

Abstract

Atmospheric aerosols have been profoundly associated with several cardiovascular and pulmonary diseases. However, the precise mechanism in terms of which species exacerbate toxicity remains unclear. Recent studies have investigated that redox-active organic species and metals present in atmospheric aerosols can initiate the endogenous formation of reactive oxygen species (ROS). Hydroxyl radical (•OH) is the most reactive form of ROS and its high levels may cause lipid peroxidation in the human body. The picture is further complicated by the fact that the atmospheric air is a pool of variety of chemical species emitted from very diverse sources. Further, the atmospheric aging of particular species may enhance/reduce the potential of endogenous ROS generation. In view of this, a study was carried out over Shillong, a high altitude site in the downwind Indo-Gangetic Plain (IGP). We found that organic aerosols over this site composed up to 78% of the mass in total, the highest among the IGP regions. In this discussion, I shall share my preliminary results of how the composition of the aerosols relates to endogenous •OH generation over the Shillong.

Design aspects and development of VEnus Neutral and Ion Mass Analyser (VENIMA)

Date: 2020-08-28
Speaker: Piyush Sharma
Venue: Google meet (https://meet.google.com/vhs-vqny-gca)

Abstract

Since Venus does not posses an intrinsic magnetic field, solar wind interacts directly with the ionosphere and hence, leads to atmospheric escape by means of photo-ionization, charge exchange and electron impact ionization. VENIMA, is a Neutral and Ion mass analyser( 2-200 amu), Which leads to determine the abundance of neutral species and ions present in Venusian atmosphere via in-situ measurements. VENIMA will help to understand the interaction of Venus atmosphere with Solar wind. I will discuss development of neutral and ions mass spectrometer and criticalities while designing.

Groundwater storage quantification and biogeochemical model development for water quality applications

Date: 2020-08-25
Speaker: Dr. Soumendra Nath Bhanja
Venue: Online Platform (Google Meet )

Abstract

The Indian Sub-Continent (ISC), which hosts the largest and densest global population, faces acute shortage of mostly drinking water and other usable waters as it is witnessing rapid rise in population, urbanization, and change in societal water use and lifestyle. Therefore to ensure groundwater sustainability across the parts of the ISC, the groundwater resources should be studied in detail. My research has been aimed to delineate the details of long-term patterns of groundwater recharge, storage change and quantification, spatio-temporal variability of groundwater storage, groundwater-surface water interaction, and also the effect of water management strategies on groundwater storage in ISC using in situ, satellite-based and numerical model simulations. Depletion of usable groundwater storage is linked with the increase of irrigated area linked with water intensive crops. The large-scale depletion of groundwater resources in Ganges basin has been found to be linked to the summertime drying of the Ganges river in recent years. A ray of hope still exists as it is found that the application of proper water resource management practices in parts of the ISC leads to groundwater storage replenishment. Oxidation-reduction reactions associated with oxygen diffusion and soil organic matter decomposition influence a number of soil biogeochemical cycles. The processes are responsible for controlling oxidation reduction potential (ORP), pH and chemical balance in the soil-water medium. My research also focuses on developing a process based model including microbial kinetics and thermodynamics for simulating the regional scale biogeochemical processes. The model is capable of simulating multiple water quality parameters at one run, for the first time in regional-scale. Water quality being an important component of water security, the approach can be widely used in Indian sub-continent and other parts of the globe for different water quality applications.

Particle acceleration in CME shocks

Date: 2020-08-25
Speaker: Ms. Shanwlee Sow Mondal (PRL Ahmedabad)
Venue: https://meet.google.com/vrx-tyqc-ftp

Abstract

Astrophysical shocks are efficient particle accelerators giving rise to power-law energy spectra and magnetic field amplification of the ambient medium. Shocks around supernova remnants are considered to be the sources of galactic cosmic rays. On the other hand, shocks driven by the Coronal Mass Ejections are prominent sources for Solar Energetic Particle events. In situ measurements show rise in particle flux at energies well above the ambient plasma's thermal energy. The fundamentals of the particle acceleration processes active in such astrophysical shock waves are essentially based on the diffusive shock acceleration (DSA) mechanism. Using a sophisticated Magnetohydrodynamics-Particle in Cell method, we have simulated a scenario where the propagation of a CME leads to the formation of a strong shock (of Alfvénic Mach, MA ~ 19). We find that such a strong shock is capable enough to accelerate the SW particles to energies ~ 10 MeV. The dominant mechanism for such acceleration comes out to be the DSA as the particle energy spectra derived from our simulation maintains a slope of ~ -3/2. We also have studied the effect of other weak shocks whose results will also be discussed.

Solar type II radio bursts in the decameter-hectometer wavelength region

Date: 2020-08-25
Speaker: Ms. Binal Patel, JRF, USO/PRL
Venue: Online

Abstract

Type II solar radio bursts are caused by magneto-hydrodynamic shocks which propagate through the solar corona and interplanetary medium. They can be observed as a slowly drifting feature in the dynamic spectra recorded from the ground and space based radio instruments. Type II bursts are associated with flares and coronal mass ejections (CMEs), hence their investigations provide important insights toward understanding the influence of transient solar activity on the corona and heliosphere. Depending on the starting frequency of the radio burst they are classified into three different groups: metric (30 MHz ≤ f ≤ 300 MHz), decameter- hectometer (decameter: 3 MHz ≤ f ≤ 30 MHz, and hectometer: 300 kHz ≤ f ≤ 3 MHz), and kilometric (300 kHz ≤ f ≤ 30 kHz) type II bursts. Out of these groups the decameter-hectometer (DH) domain is of particular interest due to its association with the energetic and wider CMEs that frequently cause space-weather manifestations. The radio bursts in the DH region are observed from Radio and plasma wave experiment (WAVES) on-board Wind spacecraft and SWAVES instruments on-board STEREO spacecrafts. In this talk, I will present the characteristics of DH type II bursts for the solar cycle 23 and 24. The bursts are classified according to their end frequencies into three categories, i.e. High Frequency Group (HFG; 1 MHz ≤ f ≤ 16 MHz), Medium Frequency Group (MFG; 200 kHz ≤ f < 1 MHz), and Low frequency Group (LFG; 20 kHz ≤ f < 200 kHz). We find that the sources for LFG, MFG, and HFG events are homogeneously distributed over the active region belt. Our analysis shows a drastic reduction of the DH type II events during solar cycle 24 which includesonly 35% of the total events (i.e. 179 out of 514). In spite of having smaller number of DH typeII events in the solar cycle 24, it contains a significantly higher fraction of LFG events (34% vs. 23%). This result suggests that cycle 24 is rich in terms of producing CMEs that are able todrive shocks up to larger heliocentric distances in comparison to cycle 23. The profiles relating CME heights with respect to end frequencies of type II bursts suggest that for HFG and MFG categories, the location for majority of CMEs (≈65%-70%) is in well compliance with ten-fold Leblanc coronal density model, while for LFG events a lower value of density multiplier (≈3) seems to be compatible. The properties of the type II associated CMEs and flares will also be discussed for each group in detail for both the solar cycle.

Geochemical Investigation of Acidalia Planum, Mars

Date: 2020-08-24
Speaker: Alka Rani
Venue: Google meet (https://meet.google.com/vhs-vqny-gca)

Abstract

Volcanism has played a significant role in the geologic evolution of Mars. Mars has experienced volcanic activity since Noachian (>3.6 Ga) to late Amazonian (< 500 million years), indicating that the planet has been thermally active throughout its history. The magma formed at Martian interior rises and erupts on the surface to forms volcanic rock. Previous studies have shown that magmatic processes played a key role in defining the chemical composition of Hesperian (3.6-3.1 Ga) and Amazonian (< 3.1 Ga) volcanic provinces. However, the thermal condition of the Noachian age (> 3.6 Ga) of Mars is still unknown. The geochemical Mapping of the Arabia Terra has shown the absence of coherent compositional signature and uniformity. The deduced geochemically distinct sub-units of Arabia Terra limits our understanding of the Noachian Age volcanism. This necessitates to thoroughly look at the evolution of these sub-units. In my presentation, I will discuss the geochemical investigation of one of the sub-unit, i.e., Acidalia Planum and its relation to the early volcanism on Mars.

Polarisation measurements of Cygnus X-1 with CZTI on-board AstroSat satellite

Date: 2020-08-24
Speaker: Mr. Abhay Kumar (PRL Ahmedabad)
Venue: https://meet.google.com/rfw-yppa-mdp

Abstract

Cygnus X-1 is a galactic high mass X-ray binary(HMXB). It is a first widely accepted black hole, with a mass of ~15 solar mass and a companion O type star of 27 solar mass. It accretes matter from the stellar wind coming from the companion. Its persistent brightness and proximity to earth(~1.85 kpc) have made it an obvious choice of study by different instruments and in different wavelength regimes. Radiation coming from the astrophysical sources can be characterized in terms of spatial image, energy spectrum, temporal evolution, and polarisation. The first three variables are well studied, but polarisation measurements are done only for few sources due to its photon hungry nature and instrumental limitations. There are different models to explain the source's geometry and emission mechanisms based on the first three variables. Polarisation measurements can break the degeneracy and give a more constraint model to explain the source. It is mainly caused by the scattering and synchrotron emission in astrophysical sources, which depend upon the geometry, magnetic field strength, and structure of the source. It is well established that CZTI, which is meant for spectroscopy and imaging purpose, can be used as Compton polarimeter above 100 kev. By fitting the histogram of azimuthal distribution of the Compton events in the detector by a cos square function gives the orientation of the electric field (Polarisation angle) and polarisation fraction(PF) of the radiation. The analysis procedure is validated by measuring the polarisation of Crab nebula, which is done earlier by Vadawale et.al. Earlier, Bragg polarimeter on-board OSO-8, INTEGRAL/SPI in 250-400kev and >400 kev, and POGO+ a balloon-borne mission in 20-180 kev gave some upper limit of polarisation. We have found the PA equal to 220 degrees in 100-500 kev, which is the same as INTEGRAL measurements. In this talk, polarisation measurements of Cygnus X-1 done using these instruments and what we have measured using the Astrosat-CZTI will be discussed.

Theoretical modeling of the diffuse aurora in Martian atmosphere

Date: 2020-08-21
Speaker: Masoom P. Jethwa
Venue: Google meet (https://meet.google.com/vhs-vqny-gca)

Abstract

Aurorae are observed on various solar system bodies. These aurorae can be either discrete, or diffuse (emission due to solar energetic particles) in nature. In the Martian atmosphere, Carbon dioxide is a major species which gets ionized by solar photon, galactic cosmic rays and solar wind electron. During nighttime, excess energy is deposited by the energetic electrons, into the atmosphere ionizing Carbon dioxide. This leads formation of diffuse aurora of CO2 + Ultraviolet Doublet emission. During December, 2014, MAVEN recorded a significant enhancement in the energetic electron fluxes. I will present and discuss the model results of hybrid model and four‐dimensional yield spectrum approach based on Monte Carlo simulation to calculate the ionization rates and limb intensities of diffuse aurora in the nighttime ionosphere of Mars.

Soft X-ray spectroscopy of the small Solar flares by XSM on-board Chandrayaan-2 orbiter

Date: 2020-08-21
Speaker: Mr. Biswajit Mondal (PRL Ahmedabad)
Venue: https://meet.google.com/gpi-kuzq-ojz

Abstract

Solar corona is very hot and hence emit high energy radiation up to a few keV. However, during the massive solar flare, the emitted radiation is extended to a few 10s of keV. Hence the study of soft X-ray spectrum of Solar corona along with the flares could be a diagnostics for the plasma properties. One of the important factors for the coronal plasma is to understand the elemental composition in it. The solar chemical composition is an important ingredient in our understanding of the formation, structure, and evolution of both the Sun and our Solar System. Also, the knowledge of the elemental compositions at different layers of the Sun helps us to improve our understanding of the energy transport from the inner to outer atmosphere and heliosphere of the Sun. Chandarayaan-2 Solar X-ray Monitor (XSM) observes the Sun as a star in the soft X-ray band of 1 – 15 keV to provide spectral measurements at a cadence of one second. In this talk, I will discuss the soft X-ray spectral modeling and the measurement of elemental abundance during a Solar flare.

Broad-band X-ray spectral characteristics of Compton-thick AGN

Date: 2020-08-20
Speaker: Mr. Abhijit Kayal (PRL Ahmedabad)
Venue: https://meet.google.com/afk-pego-zcb

Abstract

The circumnuclear matter surrounding active galactic nuclei (AGN) is thought to be responsible for obscuration and scattering of the primary continuum emission in type-2 AGN, and plays a critical role in accounting for the characteristics of the X-ray spectrum. In recent years, much emphasis has been placed upon Compton-thick AGN (N_H > 1.2 x 10^24 cm^-2) owing to the fact that a high fraction of obscured population of AGN is required to explain the cosmic X-ray background spectrum. We attempt to understand the nature of reprocessing material by modelling the broad-band X-ray spectrum of a nearby Compton-thick AGN namely Circinus galaxy. We find that the broad-band X-ray spectra over 3 – 79 KeV obtained with NuSTAR and AstroSat-LAXPC can be fitted with a model considering reprocessing of X-ray emission from putative torus viewed edge-on with column density much higher than the Compton-thick limit.

Variability of X-ray/UV/Optical emission in Seyfert 1 galaxy Mrk 509

Date: 2020-08-18
Speaker: Ms. Neeraj Kumari (PRL Ahmedabad)
Venue: https://meet.google.com/hxh-qjas-wez

Abstract

Large flux variations in X-rays and UV/optical range, on the timescale of hours to years, are very common in active galactic nuclei (AGNs). There are different proposed physical mechanisms for these variabilities depending on their timescales. To investigate the cause of variation in emitted radiation from different parts of the accretion disc, we have used multi-wavelength observations of Seyfert 1 galaxy Mrk 509 from SWIFT observatory. In this talk, I will be discussing different physical mechanisms such fluctuations in the accretion disk and reprocessing scenario, describing variability. The different techniques have been used for calculating correlation and time-lags between different energy bands. We test the existing assumptions in the standard Shakura-Sunyaev disk which is described by the power-law relating time-lag and the wavelength.

Modelling the atmosphere of comets with different volatile compositions

Date: 2020-08-14
Speaker: Sana Ahmed
Venue: Google meet (https://meet.google.com/vhs-vqny-gca)

Abstract

Comets are the most numerous objects of the Solar System, and are made up of frozen volatiles and refractory dust grains. They move in elliptical orbits about the sun, and solar heating causes the sublimation of the volatile ices, forming the cometary atmosphere or the coma. The volatile composition of the coma is generally diverse, but H2O is a primary constituent in most of the cases. This is followed by CO and CO2, whose abundance percentage with respect to H2O varies between 1% to 30%. Trace amounts of other species such as CH4, CH3OH, O2, and NH3 are also present. In some comets, the observed CO/H2O ratios are >> 1. One such comet that has a coma dominated by CO outgassing is C/2016 R2 (PanSTARRS). Solar UV radiation causes photodissociation of the sublimated parent volatile species in the coma, creating ions and radicals that drive the coma chemistry. The density in the inner region of the coma (~ 10000 km) is high enough to treat the coma gas as a fluid. In my talk, I will describe one such fluid model to study the thermodynamics of the coma. I will present the model results for different cometary compositions, whose coma activity are dominated by H2O and CO respectively. I will also discuss my model results for the coma of comet C/2016 R2.

Confirming the suspected symbiotic nature of SU Lyn : A new kind of symbiotic system

Date: 2020-08-13
Speaker: Mr. Vipin Kumar (PRL Ahmedabad)
Venue: https://meet.google.com/koz-hktt-bzt

Abstract

Symbiotic stars (Syst) are interacting binary systems typically consist of a white dwarf(WD) and a cool giant companion. Syst can be revealed through their characteristic optical spectra showing several high excitation emission lines along with Balmer series of hydrogen lines, superimposed on the continuum of a red giant. Though symbiotics have been studied since decades, a recent discovery of SU Lyn - an ordinary red giant from ground based optical observations - in X-rays gave rise to suspicion that it may harbours a hidden WD, thus making it a promising candidate of a new class of symbiotic systems. Using UV spectroscopy from UVIT instrument on ASTROSAT satellite and ground based optical-NIR spectroscopy, We have successfully confirmed the symbiotic nature of SU Lyn. This is, to the best of our knowledge, the first attempt to utilise spectroscopy capability of UVIT. The confirmation of SU Lyn as a new class of symbiotics has opened up an unknown window to discover more objects of this kind, and carries a great significance given that the currently known population of symbiotics are nearly a factor of 1000 less than the predicted one.

Chandrayaan-2 Solar X-ray Monitor: Calibration, Data Analysis, in-flight Performance, and Science Prospects

Date: 2020-08-12
Speaker: Mr. Mithun N. P. S. (PRL Ahmedabad)
Venue: https://meet.google.com/wic-ccnp-qzd

Abstract

Chandarayaan-2 Solar X-ray Monitor (XSM), designed and developed by PRL, observes the Sun as a star in the soft X-ray band of 1 – 15 keV to provide spectral measurements at a cadence of one second. The broadband X-ray spectra with XSM are used to aid estimation of global elemental abundances on the Moon as well as for independent investigations of the Sun. The design features of the XSM such as the use of Silicon Drift Detector, automated filter wheel mechanism, and onboard data processing and intelligence enable XSM to have two unique characteristics: (i) obtain spectra with an energy resolution of better than 180 eV at 5.9 keV; and (ii) maintain this spectral performance over the wide range of incident fluxes expected during different classes of solar flares ranging from sub-A class to X5 flares. XSM has been operational in lunar orbit from September 2019, and the in-flight performance of the instrument so far has been excellent and identical to that on the ground. Particularly, the observations show that the XSM has a very low background as expected and can measure the solar spectrum even during periods of extremely low activity with the flux levels an order of magnitude below the GOES A1 class. In this talk, I will discuss the aspects of ground and in-flight calibration of XSM, data analysis procedure and payload operations center activities, onboard performance, and some specific science cases that can be addressed using XSM observations along with some initial results.

Search for remnant radio galaxies in deep field surveys

Date: 2020-08-11
Speaker: Mr. Sushant Dutta (PRL Ahmedabad)
Venue: https://meet.google.com/zdv-xmaa-dbc

Abstract

The final phase of radio galaxy life-cycle, referred as remnant phase, is being characterized with the reduced AGN activity and stoppage of jets supplying energetic plasma to the lobes. Remnant radio galaxies (RRGs) are supposedly rare, and therefore, statistical study of RRGs is vital to understand jet duty-cycle, and radiative cooling mechanisms in lobes. We have searched RRGs in the XMM-LSS extragalactic field using deep 325 MHz GMRT survey and existing multi-frequency radio surveys. To achieve high completeness we use both morphological criteria as well as spectral criteria, and find an upper limit on the fraction of RRGs to be nearly 7 percent. The low-fraction of RRGs suggests that extended radio emission in lobes tends to fade quickly once AGN-jet activity switches off. In this talk, I shall explain the selection criteria, related biases and characterization of RRGs.

Understanding lunar highly siderophile element distributions

Date: 2020-08-07
Speaker: Yash Srivastava
Venue: Google meet (https://meet.google.com/vhs-vqny-gca)

Abstract

Highly siderophile elements (HSE: Re, Os, Ir, Ru, Pt, Rh, Au and Pd), are important geochemical tracers for understanding the formation and accretion of planetary bodies. Although the present estimates of the HSE in the lunar mantle are >20 times less than for Earth’s primitive mantle, they are still overabundant than those predicted by various models for HSE abundances in the lunar interior; using experimentally-derived partition coefficients for these elements and assuming core formation. Among the various models evoked to explain this overabundance, late accretion contributions to the lunar interior emerges as the most promising hypothesis. Late accretion, however, still requires explanation as the existing HSE data seemingly requires different amounts after considering gravitational focusing between Earth and the Moon. Thus, in the absence of mantle samples from the Moon, there is continued need to analyze lunar returned samples and meteorites to understand both the distribution and variability of the HSE in lunar mantle-derived melts and, ultimately, in the lunar mantle. In this talk I will describe the problem stated above and its present understanding.

Search for exoplanets: Study of line bisectors from stellar spectra and its relation with PRV measurements

Date: 2020-08-07
Speaker: Ms. Akanksha Khandelwal (PRL Ahmedabad)
Venue: Google Meet https://meet.google.com/gsb-xsyn-rcy

Abstract

Exoplanets are the planets that orbit around stars other than the sun. Since the discovery of the first exoplanet, the field has evolved, significantly and a tremendous amount of research has been going on in the field. Still, the detection or characterization of exoplanets remains important to study them in detail. The most reliable exoplanet detecting method is the radial velocity (RV) method. With the purpose of contributing to this field, a long term program has begun at PRL using the PARAS spectrograph, which is attached to our 1.2 m telescope at Mt. Abu. This program focuses on the search of sub-Neptunes to Jupiter mass planets around late F, G, and K type stars using the highly precise Doppler spectroscopy. We search for the periodic variations in RV data. Sometimes, these periodic variations can be mimicked by magnetic activity induced on the stellar atmosphere or contamination of nearby sources. In order to determine the origin of these RV variations, a technique called line bisector analysis is used. I have developed a line bisector tool for PARAS data. In this talk, I will briefly discuss exoplanets and its detecting methods as well as PARAS and its data reduction & analysis procedure, and the bisector analysis will be discussed in detail.

Observational signature of End-Dominated Collapse in Monoceros R1 Filament

Date: 2020-08-06
Speaker: Mr. Naval Kishor Bhadari (PRL Ahmedabad)
Venue: Google meet https://meet.google.com/ete-cpxi-chj

Abstract

Filamentary features are commonly observed in star-forming regions. They are elongated structures of molecular clouds and often found to nurture the star formation activities along their major axis. The presence of HII regions, embedded clumps, and the clusters of young stellar objects (YSOs) toward the filaments suggests that filaments play a significant role in the star formation processes. To study the role of filaments in star formation, we have carried out an analysis of multi-wavelength data of a star-forming complex Monoceros R1 (distance~760pc). Our observational results reveal the presence of an elongated filament (length ~14 pc). The CO molecular line data confirm the existence of an isolated and single filament, which is traced in a velocity range of [-7.8, 1.3] km/sec. The two previously known star-forming sites IC 446 and IC 447 are found to be located toward the filament's ends. A massive YSO is embedded in IC 446, while IC 447 contains several massive B-type stars. Based on the photometric analysis of point-like sources, clusters of YSOs are traced mainly toward the ends of the filament. Altogether our observational results are consistent with the End Dominated Collapse (EDC) model of star formation in filaments. The observational examples of EDC model are limited in the literature. In this talk, the observational results of our study on Mon R1 region will be presented.

Active region filaments: structure, instability, and eruption

Date: 2020-07-31
Speaker: Mr. Suraj Sahu
Venue: Online Platform

Abstract

Solar filaments are large-scale magnetic structures containing cool and dense plasma suspended in the chromosphere and corona.Filaments form both in active and quiet regions of the Sun; they are classified as active region filaments (ARFs) and quiescent filaments (QFs), respectively. The ARFs are much shorter in length-scale and time-scale in comparison with QFs, yet they undergo dramatic activation and their eruption subsequently leads to solar flares. A fundamental condition governing the formation and development of ARFs is the local coronal magnetic field topology and magnetic flux evolution through the photosphere below. The detailed observations of morphology, evolution, and dynamic processes in disturbed filaments and neighboring coronal magnetic fields during the course of the filament activation may provide clues to understand the onset and energy release mechanisms during the large-scale eruptive phenomena, which have direct impact on space weather. With this motivation, I present studies of filament eruptions from active regions NOAA 12371 and NOAA 12017. Our first analysis deals with the eruptive expansion of an ARF leading to a major solar flare of class M6.6 and a halo, fast CME, which occurred on 2015 June 22. We identify a magnetic flux rope (MFR) along the main polarity inversion line of the active region by employing non-linear-force-free-field modeling of the coronal magnetic field. Our observations reveal that, the MFR is cospatial with an Hα filament and a hot EUV coronal channel. A very remarkable finding of the study lies in the detection of elongated as well as localized HXR sources of energies up to 25 keV that lie exactly over the extended central part of the MFR. This is the first time an activated MFR has been detected in direct HXR observations. In our second ongoing work, we study recurrent homologous eruptions of three filaments leading to major flares of gradually increasing SXR intensities, viz., M2.0, M2.6, and X1.0. We study the evolution of photospheric magnetic field as well as the structural changes in the coronal magnetic configuration during a period of ≈44 hr. We discuss the observed dynamics in the framework of resistive and ideal MHD instabilities.

Study of Exoplanet Atmospheres

Date: 2020-07-31
Speaker: Vikas Soni
Venue: Google meet

Abstract

Nearly four thousand exoplanets, i.e., the planets outside the solar system (exoplanets) have been discovered in the past two decades using various ground and space-based telescopes. The composition of the exoplanetary atmospheres is governed by the physical parameters of the star-planet system. Some of these parameters are surface gravity, metallicity, stellar flux, internal heating, and orbital properties of the planet. These parameters span over a continuous range of parametric space. To simulate the atmospheric composition of these exoplanets, we need a large number of interconnected chemical reactions, along with predefined physical parameters of the system. In this presentation, I will briefly describe the detection methods along with the diversity of exoplanets. I will also discuss the factors and physical processes which affect the atmospheric composition and how we can simulate the atmosphere of these exoplanets.

Spectral and timing study of the black-hole binary MAXI J1631-479

Date: 2020-07-30
Speaker: Mr. Sandeep Rout (PRL Ahmedabad)
Venue: Google Meet

Abstract

Low-mass black hole binaries remain in quiescence for most of the time and are only detected when they undergo outburst; thus, becoming bright in the entire electromagnetic spectrum. Most of the knowledge about these systems have come from extensive study of the variation of intensity as a function of energy and time during these sporadic outbursting episodes. In the seminar, after briefly introducing the phenomenology involved, I will present the results of the spectral and timing analysis of a new X-ray binary, MAXI J1631-479, that was discovered in early 2019 and was observed by almost all X-ray telescopes. By tracking the source for the entire duration, we are able to understand the evolution of the source and pin down physical models for timing variability. Using reflection spectroscopy, we could constrain physical parameters like BH spin and inclination of the binary.

The case for Interstellar comets/Asteroids Part II - Detection and Analysis of first IS visitors

Date: 2020-07-28
Speaker: Mr. Aravind K. (PRL Ahmedabad)
Venue: Google meet

Abstract

As described in the previous seminar, Interstellar comets have been a topic of interest from the past years. There have been various theories and speculations regarding the existence of such a class of comets and the probability of their detection in our solar system. It was not until 1993 that a satisfactory result related to the number of comets expected to be detected, in a century, was calculated. Later, in 2017, as a breakthrough finding, came the detection of the first interstellar object 1I/'Oumuamua. Two years later, astronomers were gifted with a direct opportunity to closely study the remnants of the formation of another stellar system by observing the first ever interstellar comet, 2I/Borisov, to be detected passing through the solar system. In this talk, I will discuss in-brief, the properties of both interstellar objects, 1I/'Oumuamua & 2I/Borisov as observed by astronomers across the world and cover in-depth the observation of 2I/Borisov using various techniques by our group in PRL, using MIRO, Abu and HCT, Hanle.

Grimaldi Basin on the Moon: Evidence for volcanism and tectonism during the Copernican period

Date: 2020-07-24
Speaker: Tanu Singh
Venue: Online

Abstract

The availability of high-resolution datasets from various missions have greatly improved our understanding of the Moon by revealing volcanic and tectonic activities that have occurred in the recent past. We have found evidence of such events in the Grimaldi Basin, a Pre-Nectarian basin located near the western edge of the Oceanus Procellarum. Moon Mineralogy Mapper (M3), FeO wt%, and TiO2 wt % data have been used to study the compositional make-up of the Grimaldi mare basalt. Additionally, morphological studies and crater chronology have been carried out using moderate to very high-resolution images from Lunar Reconnaissance Orbiter (LRO) to decipher the geological evolution of the Grimaldi Basin. In this study, we have found that in the south-central part, the basin experienced Copernican aged volcanism ~700 Ma ago, resulting in the formation of olivine bearing basalts with high FeO and TiO2 content. Cross-cutting of small Copernican craters by fresh wrinkle ridges and lobate scarps have been observed at several places, suggesting that tectonic activities also occurred in the basin during the past ~50 Ma-1 Ga.

Distance estimation from Gaia parallaxes

Date: 2020-07-23
Speaker: Ms. Namita Uppal (PRL Ahmedabad)
Venue: Google meet

Abstract

Stellar distance is an important parameter in astronomy. Most of the methods used to evaluate distance depend on the stellar type, their luminosity, and age. Parallax is the only method that is applicable to all the stars irrespective of their classification and it depends solely on geometry. The ground-based parallax observations suffer from atmospheric disturbances causing limited precision in the position measurement, which calls for the need to go for space missions. One of the dedicated space based missions - Gaia (successor of Hipparcos) was launched by ESA in December 2013 for precise astrometric measurement. It has measured the parallax of approximately 1.33 billion stars with microarcsec astrometric accuracy. In this talk, I will discuss the problems associated with the usual distance estimation i.e., inverse parallax method and the techniques devised to deal with them in a self-consistent manner using Bayesian inference.

Hydrogeological Processes in Kerala: Insights from Oxygen and Hydrogen Isotopes in groundwater Abstract:

Date: 2020-07-21
Speaker: Mr. Amit Pandey
Venue: Online Platform (Google Meet )

Abstract

The state of Kerala, located in the southwestern tip of India is bounded by the Arabian Sea in the west and the Western Ghats in the east. Though it occupies only 1.2% of the total area of the country, it accommodates 3% of the country's population. In spite of copious annual average rainfall of ~3100 mm, the state of Kerala has a high level of dependency on groundwater for agriculture and drinking purposes, due to geohydrological reasons compounded by the high population density and agrarian economy. The groundwater in Kerala is stored in four types of aquifers in the region, and recharged by rain and surface water. In recent decades, Kerala is facing severe groundwater problems due to variety of reasons such as seawater intrusion during summer, drying of wells, and geogenic as well as anthropogenic pollution. Therefore, it is important to understand hydrogeological processes and factors which affects availability and quality of groundwater. This knowledge is important to manage and ensure groundwater sustainably in the region. A large body of current knowledge about groundwater in Kerala is derived from the seasonal fluctuations in water table/ piezometric level and basic chemistry of water. However, there are some knowledge gaps which needs to be bridged through application of oxygen and hydrogen stable isotopic tracers. This study is aimed to address following scientific questions: (1) Is there any hydraulic connectivity between four types of aquifers in Kerala? (2) What are the different sources of groundwater recharge? (3) Can we identify aquifers/regions recharged by NE Monsoon? (4) Are there any linkages between wetlands and groundwaters? (5) Can we estimate average travel time of groundwater from highlands to coast? (6) Does evaporation affect the groundwater of this humid region? Tentative answers to the above questions will be attempted in the seminar.

Optical design of the Near IR Imager, Spectrometer & Polarimeter (NISP)

Date: 2020-07-21
Speaker: Ms. Archita Rai
Venue: https://meet.google.com/jqt-pvdj-vqg

Abstract

NISP (Near-Infrared Imager, Spectrometer & Polarimeter) is a multi-faceted instrument for the 2.5 m telescope. The ability to perform imaging, spectroscopy and polarimetry in the wavelength range of 0.8 micron to 2.5 micron in a straight-through optics in a single instrument, makes the optical design interesting. In this talk, I will be discussing about the conceptual background for the optical design of a Near-Infrared instrument and then discuss the optical design of NISP. It encompasses the switching from one mode of operation to another which shall be explained. Apart from the imaging and spectroscopic specifications, the instrument is unique in having a single-shot simultaneous 4 position angle measurement technique for polarisation. The talk will summarize the achieved specifications for the NISP instrument and the efforts incorporated to fix the odd challenges an optical designer has to go through.

Wave heating of lower Solar atmosphere

Date: 2020-07-21
Speaker: Mr. Hirdesh Kumar
Venue: Online Platform

Abstract

The complete understanding of the heating of lower solar atmosphere (i.e. chromosphere) still needs investigation. To address the chromospheric heating problem, the following mechanisms have been proposed by solar researchers: (I) mechanical heating by waves (Alfven 1947; Schwarzschild 1948; Narain & Ulmschneider 1996), and (II) Joule heating associated with magnetic field reconnection (Parker 1988) and the resistive dissipation of electric currents (Robin & Moore 1984). In this connection, the analysis of Jefferies et al. (2006) using the low- resolution (~5.2 arcsec/pixel) Doppler velocity observations of photosphere and chromosphere, suggests that the acoustic p-modes (2-5 mHz) which generate inside the convection zone of the Sun can also propagate into the higher solar atmosphere along the inclined magnetic fields and thereby can heat the solar chromosphere by dissipating their energy. However, their observations were insensitive to the signal from small-scale convective cells. In this talk, I will discuss the propagation of low-frequency acoustic waves & their role in the heating of solar chromosphere, along with our planned observations using high resolution (~0.2 arcsec/pixel) chromospheric Ca II 8542 Angstrom Doppler velocity observations obtained from the Multi-Application Solar Telescope (MAST) of USO/PRL in co-ordination with the high resolution (~0.5 arcsec/pixel) photospheric Fe I 6173 Angstrom Doppler velocity observation obtained from HMI instrument aboard SDO spacecraft.

The case for Interstellar comets/Asteroids Part I - Speculations and Conclusions

Date: 2020-07-17
Speaker: Mr. Aravind K. (PRL Ahmedabad)
Venue: Google meet

Abstract

After the pioneering work by Oort (1950), it is believed that long period comets (orbital period greater than 200 years) are originated in the Oort Cloud, a hypothetical spherical reservoir surrounding the solar system at about a distance of 1000-200,000 AU. Solar system formation theories suggest that comets were formed in the outer edge of the planetesimal disk, perturbed by the giant planets and thrown into their present location in the Oort cloud. This mechanism was so inefficient that only a fraction of the comets formed were trapped into the Oort Cloud whereas the rest were lost to the interstellar medium. If this physical process of solar system formation is typical, then other stars in the solar neighbourhood are also expected to possess planets and comet like bodies. These systems would also have lost a large fraction of comets into the interstellar medium. Hence there should be a large population of extrasolar comets with composition and density distribution similar to that of the parent star system. For a long time, astronomers have been interested in knowing whether these extrasolar comets can be detected since they are direct opportunities to closely study the remnants of the formation of another stellar system. In this talk, I will discuss in brief, the theories and hypothesis, that have been evolving for a very long time, regarding the existence and possible detection of interstellar comets. In Part 2, I will be discussing in-depth the detection and analysis of 2I/Borisov by astronomers across the world as well as by our group in PRL using MIRO and HCT.

Deep sea foraminifera Abundance in Central Equatorial Indian Ocean since last glacial maxima: Effect of Productivity and Bottom Water Oxygenation

Date: 2020-07-17
Speaker: Ms. Nisha Bharti
Venue: Online Platform (Google Meet )

Abstract

Benthic foraminifera are widespread and diversified organism in the marine environment and they have a significant role in the deep-sea food web and ocean carbon cycle. They play a pivotal role in the study of paleoclimate, because of the potential capacity of fossilization of their shells. To understand the dependency of benthic foraminifers on overhead productivity, a regional process and deep-water oxygenation, a global process, during the past ~19 ka, a sediment core from the central equatorial Indian Ocean was investigated. Towards this, foraminifera from six-time intervals were separated for benthic foraminiferal abundances and dominant assemblages. The study revealed changing bottom water conditions, especially in terms of change in input of organic carbon to the deep sea and bottom water dissolved oxygen concentration during time period of the analysed samples. Variations in geochemical parameters showed good correlation with the dominant foraminiferal assemblage. This also supports the findings that the dominant assemblages are not only responding to regional processes like organic productivity but also to the global climatic changes controlling the deep-sea oxygenation. This study concludes well oxygenated bottom water throughout Holocene (2.1-12.9 ka BP) and poorly oxygenated bottom water during deglaciation(12.0-17.0 ka BP) and Last glacial maxiam.(17.0-19.3 ka BP).

Carbonates in CM/CI chondrites: Constraint on physico-chemical condition of aqueous alteration

Date: 2020-07-17
Speaker: Shivani Baliyan
Venue: Online

Abstract

Carbonates are a minor alteration product constituting ~1.4 - 2.8 vol% in CM chondrites. Previous studies have shown that calcium carbonate (CaCO3) (mainly calcite, possibly mixed with aragonite) is the dominant carbonate mineral phase in CM chondrites; minor amounts of dolomite (CaMg(CO3)2) also occur, although dolomite disappears in the most highly altered meteorites. The CI chondrites contain four carbonate minerals: calcite, dolomite, breunnerite (Mg,Fe,Mn)CO3, and siderite FeCO3. In this work, we have focused on the occurrence and mineral chemistry of carbonates in CMs and CIs, which are believed to have precipitated from aqueous solutions circulating on their parent body during a period of extensive alteration of CM/CI precursor material. The carbonates in the different CM samples vary in shape, sizes and modes of occurrences. Apart from isolated grain, accumulated at one place, carbonates are often found scattered throughout the matrix. The twinning of carbonate grain often suggests deformation induced via directed stress by impact processing. Compositional variations in the carbonates could indicate the changing “micro-environment” (micron to cm scale) and correspond to different episodes of carbonate formation in the asteroid parent body.

Chronology of Quaternary Glaciation in the Central and Northwestern Himalaya: Findings in the Recent Decade

Date: 2020-07-14
Speaker: Mr. Partha Sarathi Jena
Venue: Online Platform (Google Meet )

Abstract

The glaciation in Himalaya is a combined influence of climate and orography. To understand the local response of global climate change, a proper chronology of glaciation events is necessary. The Higher Himalayan Range in the south and Karakoram Range in the north play an important role and affect the moisture transport in the region. The dominance of moisture sources varies between monsoon-influenced Central Himalaya and westerlies influenced Northwestern Himalaya. With limited dates on glaciation events earlier, it was observed that the Himalayan glaciers only responded to the Indian Summer Monsoon irrespective of the geographical position. The most interesting/intriguing observation was that no glaciation event was found during the last glacial maximum event in the Nubra valley and the Ladakh Range, which lie in the north of higher Himalaya and are presently influenced by westerlies. Recently, several studies have reported many glacial events dated using both terrestrial Cosmogenic Nuclide and Luminescence dating methods. In this presentation, the timing of glaciation events from recent studies in the valleys from Karakoram, Ladakh, Zanskar, and Higher Himalayan ranges along with the factors responsible for driving quaternary glaciation will be discussed.

Impact of Hall MHD on Development and Evolution of Magnetic structures during Reconnection

Date: 2020-07-14
Speaker: Ms. Kamlesh Bora
Venue: Online Platform

Abstract

We have extended the well-established magnetohydrodynamic model EULAG-MHD to include the Hall-magnetohydrodynamics. Such an extension is necessary to study a variety of physical systems where the magnetic reconnection scale is of the order of ion inertial scale. Examples of such systems include solar transients, magnetosphere and magnetotail reconnections and laboratory plasmas. The results of two set of simulations using EULAG- HMHD will be discussed in the talk. The first simulation with and without the Hall term is initiated with a sinusoidal magnetic field to benchmark the code. Notably, the magnetic reconnections onset earlier in presence of the Hall term---signifying the reconnections to be faster. Additionally, the Hall term generates magnetic field directed out of the reconnection plane and destroys any inherent symmetry to ultimately make the evolution three dimensional. The resulting three dimensional reconnections develop magnetic flux ropes and magnetic flux tubes. Projected on a plane, the ropes and tubes appear as magnetic islands which with time further breaks into secondary islands and finally coalesce to generate an X-type neutral point. These findings are in agreement with the theory and contemporary simulations of Hall- magnetohydrodynamics, benchmarking the the Hall extension. A novel set of simulations are also executed to explore the activation of a magnetic flux rope from sheared magnetic arcades. Such simulations are instructive to understand solar transients. The results show development of a magnetic flux rope and its ascend as the rope evolves through intermediate complex structures---ultimately undergoing secondary reconnections which locally breaks the flux rope. Interestingly the breakage of the rope occurs earlier in presence of the Hall term, signifying a faster dynamics that leads to magnetic topology favourable for reconnections. We found that the evolution of magnetic field in three dimension is much more complex than their two dimensional idealisation.

Magnetic flux rope eruptions from complex active regions: Initiation and early evolution

Date: 2020-07-09
Speaker: Mr. Prabir K. Mitra
Venue: Online Platform

Abstract

Solar transient phenomena include eruptive filaments, flares, coronal mass ejections (CMEs) etc., which are among the most spectacular and most energetic events occurring in the solar system. Observationally it is established that flares are frequently associated with filament eruptions and CMEs and such flares are called eruptive flares. The ‘standard flare model’ which is also known as the ‘CSHKP model’, considers the presence of a magnetic flux rope (MFR) as a pre-requisite whose activation and upward rising motion is essential for the initiation of a flare. However, the formation and triggering of the MFR is still less understood and has remained a topic of discussion in solar physics. Our multi-wavelength observational analysis, complemented by coronal magnetic field modeling have provided remarkable results on the formation and activation of MFRs in the form of coronal hot channels as well as on the origin of pre-flare activities. Our analysis further reveals that small-scale activities can initiate a series of small-scale activities that lead to a large-scale eruption which is similar to a ‘domino effect’. It is also understood that sufficient storage of magnetic energy can enable even mini-filaments to lead to a CME and large flares, provided overlying magnetic conditions are favorable for eruption. Further, analysis of magnet free energy evolution has provided important information on the capability of active regions to produce powerful eruptive events.

Exposed subsurface water-ice within the northern mid-latitude craters on MarsMulti-isotopic and (S)TEM Investigations of Presolar Silicates

Date: 2020-07-03
Speaker: Harish
Venue: Online

Abstract

One-third of the planet Mars is rich in water-ice which is mostly preserved a few meters below the surface. Identification of new water-ice rich regions is indeed required to understand their spatial spread across Mars and has a vital role for future landing/robotic missions on Mars and even for the in-situ resource utilization. Recent high-resolution visible images and spectral datasets provide more diagnostic evidence for water-ice. In this study, we have discovered water-ice exposure within two craters (~5000 km apart) located in the northern hemisphere of Mars. These exposures are found in the crater wall and over the crater floor deposits. We found that at one location, the exposed ice is stable after one week of interval, which provides a direct proof for the slow rate of sublimation of exposed ice. We determined that these craters are formed a few tens of million years ago. But, the ice-deposits within the craters is exposed within a million year ago. Thus, this study provides comprehensive evidence to substantiate that there will be widespread distribution of water-ice few meters below the surface of Mars.

The spontaneous generation of three dimensional magnetic nulls and study of their dynamics during an eruptive event

Date: 2020-06-30
Speaker: Ms. Sushree Nayak
Venue: Online Platform

Abstract

The magnetic null points are well known potential sites of magnetic reconnection in the solar corona. Although their ubiquity in the proximity of coronal transients are thoroughly studied, their generation was unclear in the first place. To investigate this problem, in our work, we have explained two cases analytically, where magnetic null points are generated as the self- organized states towards the end of the magnetohydrodynamic (MHD) evolution followed by repeated magnetic reconnections. The final state of the simulation also shows a conservation of the topological degree in the volume. For a reference, the conservation of topological degree means that the number of positive and negative null points within a volume remains equal irrespective of the system’s dynamics. Alongside this work, we have also explored the dynamics of 3D nulls during an X-class flare associated with a coronal mass ejection (CME) where the eruption mechanism was not straightforward. We have tried to study the change in the topological behaviour and found one 3D null, a set of twisted magnetic field lines and a set of sheared arcades near the vicinity of the flaring region. The dynamics of these complex topologies is then analyzed from the MHD simulation and the process of eruption seems to follow a break-out model scenario. Details of the work will be discussed in the seminar.

Glaciation in the Erebus Montes region on Mars: Insights from debris covered glaciers in the low lying regions

Date: 2020-06-26
Speaker: Rishitosh Sinha
Venue: 04.00 PM (Online)

Abstract

Martian glacial landforms constitute up to nearly 10% of the polar caps, which suggests glacial processes to be a more relevant component of the Mars’ water cycle than they do for the water cycle in terrestrial systems. Lobate debris apron (LDA) and lineated valley fill (LVF) have been presented as the evidence of glacial landforms in a number of previous studies, and the integrated analysis of the flow extent, flow patterns, and age of these landforms have led to the suggestion that the late Amazonian glaciation was very extensive in nature. While most of the LDA and LVF have formed over the high standing mesa in the northern and southern mid-latitudes, evidence for glaciation on the low-lying mesa are infrequent. Here we show evidence for extensive glaciation on the low-lying mesa distributed within the Erebus Montes region on Mars. With multiple glacial landforms (LDA, LVF, and crater interior flows) indicative of integrated flow patterns, this region hold clues for extensive glaciation as a result of redistribution of polar ice to the mid-latitudes during the higher obliquity excursions period of the late Amazonian on Mars. In aggregate, the results add another element to the emerging evidence for the importance of the glacial process in shaping Mars geomorphology and implies that past climatic conditions were adequate to produce debris covered glaciers in the lowland regions on Mars.

Statistical study of radio-loud and radio-quiet Earth-reaching coronal mass ejections and their influence on cosmic ray intensity and geomagnetic storms

Date: 2020-06-25
Speaker: Dr. Hema Kharayat
Venue: Online Platform

Abstract

We present a statistical investigation and geo-effectiveness of Earth-reaching CMEs of solar cycles 23 and 24 in regard to their ability to produce interplanetary DH type II radio bursts during Sun-Earth transit. CMEs associated with DH type II radio bursts are termed as radio-loud (RL) while rest of the CMEs are called radio-quiet (RQ). We further explored the effects of these two CME populations on the variation of cosmic ray intensity (CRI) and occurrence of geomagnetic storm (GS). We found 60% Earth-reaching CMEs as RQ and only 40% as RL. The mean speed of RL CMEs ( 1170 km s^-1) was found to be significantly higher (almost twice) than the mean speed of RQ CMEs ( 519 km s^-1) at near-Sun region while their speed became comparable ( 536 km s^-1 for RL and 452 km s^-1 for RQ CMEs) at near-Earth region. The yearly-averaged speeds of Earth-reaching CMEs follow solar cycle variations. The CRI and geomagnetic Dst index are found to have good negative correlation with speed of Earth-reaching CMEs. RL CMEs were found to be more effective in producing CRI depressions and GSs in comparison to RQ CMEs; in about 70% cases RL CMEs produced CRI depression and GSs earlier than the RQ CMEs. Superposed epoch analysis suggests strongest depression in CRI occurs 2-5 days and 4-9 days after the onset of RL and RQ CMEs, respectively. Further, GS events show a time-lag of 1-5 days and 3-8 days, respectively, with respect to RL and RQ CMEs.

Be/X-ray binary Pulsar 2S 1417-624 : A case study during quiescence

Date: 2020-06-24
Speaker: Ms. Shivangi Gupta (PRL Ahmedabad)
Venue: Google Meet

Abstract

Be/X-ray binary (Be/XRB) pulsars are the major sub-class of High Mass X-ray Binaries (HMXBs). About 67% of the known population of HMXBs belongs to this category. The neutron stars in these systems are powered by the matter accreted from the circumstellar disk of the massive Be companion, at periastron passage. The Be/XRB pulsars show a wide variability in terms of their luminosity. However, the quiescent emission from these pulsars (i.e., emission at extremely low mass accretion rates) is poorly studied as the sources are extremely faint and difficult to observe. Recent observational evidence challenges the present understanding about quiescence emission. In this talk, I will present a case study of Be/XRB pulsar 2S 1417-624 during its quiescence state and discuss the results in light of present theoretical understanding.

Be/X-ray binary Pulsar 2S 1417-624 : A case study during quiescence

Date: 2020-06-24
Speaker: Ms. Shivangi Gupta (PRL Ahmedabad)

Abstract

Energy dependent phase resolved Crab polarimetry using AstroSat CZTI

Date: 2020-06-11
Speaker: Ms. Aarthy E. (PRL Ahmedabad)
Venue: Google Meet

Abstract

The Crab pulsar and its nebula is one of the most favorite and well studied Pulsar Wind Nebula (PWN) over all the ranges of the electromagnetic spectrum. Though the field of observational astronomy has evolved tremendously over time with improvements in imaging, timing, spectroscopy, and polarimetry studies, the geometry and the emission mechanism from the Crab pulsar itself are not completely known. Measuring polarization helps in studying the emission process, magnetic field and geometry of source and its surrounding medium. Radio, Optical, and X-ray/Gamma ray polarization of the Crab pulsar and nebula have been reported a number of times. There are various models compatible with observational characteristics, while multiple models explain the features of Crab light curve and spectra. One distinguishing feature of these models is their phase-dependent polarization signature. Phase resolved polarization measurements of the Crab pulsar in hard X-ray regime was reported for the first time by Vadawale et al., 2018 using the CZT Imager on-board AstroSat. A swing in the polarization angle was reported within the pulse period and the off-pulse region was found to have high degree of polarization. Following this, we used ~1800 ks of CZTI Crab data and performed phase resolved polarization over different energy ranges (dynamic and independent from 100 - 380 keV). In this talk I would present the latest results of Crab polarization using AstroSat CZTI.

Hydrometeorological processes and evaporation from falling rain in Indian sub-continent: Insights from stable isotopes and satellite data

Date: 2020-06-09
Speaker: Mr. Harsh Oza
Venue: Online Platform (Google Meet )

Abstract

Rigorous analysis of measured isotopic composition (δ18O and δD) of 556 daily rainwater samples collected at four Indian stations viz., Jammu, Jorhat, Hyderabad and Ahmedabad, is done in conjunction with satellite and model-derived meteorological and isotopic parameters to discern prominent hydrometeorological processes and factors in four different climatic zones in the Indian subcontinent. A new Indian Meteoric Water Line (IMWL), better representing the different climatic zones, including the semi-arid western India, has been defined: [δD = (7.6±0.1) δ18O + (8±1); R2 = 0.96; P < 0.05; N = 556]. The lower slope of IMWL compared to the Global Meteoric Water Line signifies the role of evaporation from falling rain throughout the Indian subcontinent, though it is surrounded by large marine water body, and bordered by lofty Himalayan mountains in the north obstructing the monsoonal winds. We have tried to quantitatively estimate the evaporative loss from the falling raindrops. In this talk, I will be discussing some of the important results and inferences obtained from this study.

Origin, evolution and space weather consequences of CMEs

Date: 2020-06-03
Speaker: Mr. Ranadeep Sarkar
Venue: Online Platform

Abstract

A heterogeneous aggregate dust grain model. An application to cometary polarization

Date: 2020-05-28
Speaker: Dr. Prithish Halder (PRL Ahmedabad)
Venue: Google Meet

Abstract

In this work we introduce a heterogeneous aggregate dust model in order to replicate the polarization-phase curve observed in comets. Considering the findings of dust morphology from Rosetta/MiDAS, we introduce grain polydispersity of upto ±40nm and fractal dimension less than 2. Also we increase the size of the aggregates by considering hierarchical growth giving rise to hierarchical aggregates. With increasing polydispersity the degree of linear polarization indicates an abrupt reduction in the slope of the polarization-phase curve in the angular range 20 - 90 degrees. On the other hand with increasing size parameter(X), polarization reduces till X=50 and then increases and remains within P_max = 20% - 30% , P_min = 2% and inversion angle around 20 degrees. The polarization-phase curve predicted by the modeled heterogeneous, polydisperse aggregates agrees well with the observations for 1P/Halley and 67P/C-G. Finally the heterogeneous dust aggregate model indicates that grain polydispersity, composition and size of an aggregate shapes the observed polarization-phase curves for various comets.

Meteorological observations of convective vortices and simulation of dust lifting within a dust devil

Date: 2020-03-12
Speaker: Shefali Uttam
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The lower atmosphere of Mars is highly turbulent. Vortices form in the lower part of boundary layer due to convective heating of the surface by solar flux. A pressure drop is observed within a vortex which is accompanied by a rise in air temperature, and change in wind velocity. If the winds are strong enough and dust is available, then the vortex lifts dust into the atmosphere and are known as dust devils. On Mars, dust devils play an important role to inject dust grains into the atmosphere to maintain the haze and can significantly affect the global dust loading. I will discuss about the detection of these vortices using REMS data on board Curiosity. My initial analysis of data from mission sol 1545 to 1660 shows a detection of 80 convective vortices. The observations shows a distinct rise in vortex activity around noon hours between 12:00 and 15:00 Local Mean Solar Time (LMST). These vortices are also accompanied by UV intensity drop giving a possibility of occurrence of dust devil. I will also discuss about the modelling of the dust distribution within a dust devil. Our model results show a concentration of ~〖10〗^3 particles/cc near the surface during a dust devil condition on Mars. We also estimate a dust flux of ~3×10-3 kgm-2s-1, which lies in the estimated range of dust fluxes from dust devils at the Mars Pathfinder site varying between ~6×10-4 kgm-2s-1 to ~5×10-3 kgm-2s-1.

Triggering of a solar filament eruption and associated flare

Date: 2020-03-12
Speaker: Mr. Suraj Sahu (USO, PRL Ahmedabad)
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Solar filaments are large magnetic structures confining cool (T ~ 10^4 K) and dense (ne ~ 10^17 m^{-3} ) plasma in the hot solar corona. Typically, the filament plasma is 100 times cooler and denser than its coronal surroundings. Depending upon the type of magnetic environment, in which filaments form, they are classified as: active region filament (ARF), intermediate filament (IF), and quiescent filament (QF). Study of active region filaments is key to understand the evolution of magnetic fields of active regions and its role in powering solar eruptive phenomena, viz., flares and coronal mass ejections (CMEs). With these motivations, we study the eruption of an active region (AR) filament from AR NOAA 12371 on 22 June 2015, which led to a major M6.6 solar flare and a halo fast CME. The study utilizes data from Atmospheric Imaging Assembly (AIA) and Helioseismic Magnetic Imager (HMI) on board Solar Dynamics Observatory (SDO), Big Bear Solar observatory (BBSO), and Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). The event exhibited an active pre-flare phase during which a hot EUV coronal channel (co-spatial with filament channel) was in build-up stage and displayed hard X-ray emission up to 25 keV. As such, this is the first evidence of HXR coronal channel. The Non-linear-force-free-field (NLFFF) modeling of coronal magnetic field exhibited a magnetic flux rope (MFR) oriented along the polarity inversion line (PIL) and co-spatial with the coronal channel. We observe significant changes in the AR’s photospheric magnetic field at the activity site during an extended period of about 42 hours in the form of rotation of sunspots, moving magnetic features, and flux cancellation along the PIL. Prior to the flare onset, the hot channel underwent a slow rise phase (~14 km/s) for about 13 min which is followed by a fast rise (~ 90 km/s). The slow to fast transition of the hot channel precisely divides the pre-flare and impulsive phase of the flare which points toward the feedback process between the early dynamics of the eruption and the strength of the flare magnetic reconnection.

Multi-isotopic and (S)TEM Investigations of Presolar Silicates

Date: 2020-03-06
Speaker: Dr. Manish N. Sanghani
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Primitive meteorites, interplanetary dust particles and comets contain tiny dust grains that have unique isotopic characteristics very distinct from the normal solar system values. Highly abnormal isotopic compositions of these grains can not be explained by any physical or chemical processes within the solar system. These grains formed in the winds of massive stars and in the ejecta of stellar explosions even before the sun was born, known as presolar grains. Presolar ‘stardust’ grains are the direct snapshots of the stellar nucleosynthesis, and laboratory analyses of these grains provide excellent opportunity to better understand stellar and interstellar processes of grain formation, alteration and destruction. Studying presolar silicates has some advantages over studying other refractory phases. Unlike the other refractory phases, presolar silicates can only be discovered in situ within the fine grained matrices of primitive extraterrestrial samples by high resolution isotope imaging technique using the NanoSIMS ion probe, and hence they are not altered by any chemical treatments. In addition to that, presolar silicate abundances are higher as compared to other presolar phases and they also register a variety of stellar sources. The first part of this talk will describe the in-situ discovery of presolar silicate and oxide grains from the fine grained matrices of two different carbonaceous chondrites Isheyevo and NWA 801. Stellar sources of oxygen anomalous grains found in this study will be discussed. Results of multi-isotopic and (S)TEM investigations of some of the presolar silicates will be presented and grain condensation and alteration will be discussed. Lastly, results of high resolution, multi-isotopic measurements of some of the presolar silicates will be discussed and some new insights on the galactic chemical evolution will be presented. The talk will be concluded by summarizing the main results and brief discussions on the future prospects of this work.

Source extraction algorithms for deep radio surveys

Date: 2020-03-05
Speaker: Mr. Sushant Dutta (PRL Ahmedabad)
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The source extraction in deep radio surveys pose challenges as, unlike optical/IR surveys, the PSF and the background RMS vary across the image. Since the source density is large in deep radio surveys, there is always a chance of source confusion, which in turn affects the background RMS estimation. Rudimentary source extraction algorithms available in the literature are inefficient to produce a complete and reliable source catalogue, with accurate astrometry and flux estimation, in case of diffuse and extended radio sources. These factors can be taken care of in Python Blob Detection and Source Finder (PyBDSF) algorithm developed mainly to serve the need of low-frequency radio surveys. I shall discuss the working principle of PyBDSF and the results of source extraction algorithm applied to deep 325 MHz GMRT image.

Carbon, Nitrogen analyses on graphitic inclusions within IAB type Iron meteorite

Date: 2020-02-28
Speaker: Vikram Goyal
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Graphite found as inclusions in non-magmatic Iron meteorites formed by different crystallisation path have shown to have a very distinct petrological association with the metal. These graphites are believed to have carried primordial composition and in many cases preserved it. Hence, these primitive achondrites serve as an important sample disclosing various early Solar system processes. To further our understanding related to the inclusions in iron meteorites, their formation and preservation of primordial composition, we analysed Carbon and Nitrogen isotopes in a few graphitic inclusions from Kendall County meteorite. Kendall County is an IAB-type iron meteorite, structurally hexahedrite having graphite inclusions which are distributed all over the meteorite surface with sizes ranging from submicron to hundreds of microns. Graphite inclusion in schreibersite and troilite from Kendall County were analysed using PRL NanoSIMS in multi collection mode including Ni-58 along with C and N isotopes. Inclusions indicate lighter delta 13C in graphite within the metal than the reported value for graphite embedded within silicate. The lower value of delta 13C also points out that the inclusion preserved the primordial composition, and probably the parent meteorite went through only partial melting temperatures.

Carbon fixation in the oxygen minimum zones of the ocean

Date: 2020-02-25
Speaker: Mr. Himanshu Saxena
Venue: Ground Floor Lecture Hall

Abstract

Primary production is one of the most important metabolic process and about half of the global primary production (~50 Peta gram of carbon per year) is generated in the euphotic layer of the ocean. But about 75% of the global ocean is dark ocean i.e., below ~ 200 m depth, with more than 98% of the global dissolved inorganic carbon pool. Recent researches showed that carbon fixation also occurs in the dark ocean. This dark carbon fixation (chemoautotrophic) has been suggested to contribute significantly to the global ocean carbon budget, with ~2% of the total estimated yearly marine primary production. In this seminar, carbon fixation in the oxygen minimum zones of the ocean will be discussed.

Chemistry and Modeling of Martian Ionosphere

Date: 2020-02-14
Speaker: Siddhi Shah
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The Martian ionosphere can be divided into D, E and F regions. We have studied the chemistry of lower and upper ionosphere of Mars (D and E region). This presentation is based on my thesis work. I have calculated photo-ionization rates, photo-electron impact ionization rates of atmospheric gases, and photo-electron flux by using AYS method in the upper ionosphere of Mars. I have also used energy loss model to calculate production rates of atmospheric ions in the lower ionosphere of Mars. Using these production rates, densities of ions and electrons are calculated at different altitudes in the lower and upper ionosphere of Mars. We have developed a seasonal dependent energy loss model due to impact of GCR for the calculation of ion production rate at different altitudes and latitudes in presence and absence of dust storms. I have also studied the effects of solar X-ray flares in D and E region ionosphere of Mars. First time I have reported that hard X-ray is one of the major sources for producing D region ionosphere of Mars.

High Energy Emission from Pulsars with AstroSat-LAXPC

Date: 2020-02-13
Speaker: Dr. Varun, Raman Research Institute, Bangalore

Abstract

Astrosat is India's first dedicated multi-wavelength space observatory. The Large Area X-ray Proportional Counter (LAXPC) is one of the major payloads on AstroSat, which covers a 3-80 keV energy range. The three LAXPC units on AstroSat have a large effective area which gives it very good timing and moderate spectral resolution. Neutron stars have the most powerful magnetic field strength of 1012-1015 G. One interesting manifestation of the strong magnetic field is the cyclotron resonance scattering feature (CRSF) which is seen in the spectrum of accretion powered X-ray pulsars. I present the results of pulse-phase-resolved spectroscopy of the continuum and CRSF parameters of two high mass X-ray binaries (HMXB) 4U 1538-52 and 4U 1907+09 using Astrosat-LAXPC observations. For both the sources, the cyclotron line parameters show a strong pulse phase variation. For 4U 1538-522, we confirm a long term increase in the centroid energy of the CRSF. For 4U 1907+09, intensity resolved spectral analysis of the initial flare in the light curve shows that the CRSF parameters do not change with a change in luminosity by a factor of 2.6. I also present some results on the high energy emission of four isolated neutron stars with AstroSat-LAXPC observations. This study is a demonstration of methodologies to handle these sources and the capability of this instrument for them.

Investigating high-energy Solar corona with sounding rockets

Date: 2020-02-12
Speaker: Dr. P. S. Athiray
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The Focusing Optics X-ray Solar Imager (FOXSI) is the first solar dedicated sounding rocket experiment to demonstrate direct focusing hard X-ray (HXR) imaging and spectroscopy, to investigate the fundamental processes of energy release in the solar corona. Past solar HXR instruments have used indirect imaging techniques with limited dynamic range and sensitivity. With the recent technological advances, FOXSI has conducted three successful rocket flights in the years 2012, 2014 and 2018. I will present an overview of the FOXSI rocket experiment, instrumentation upgrades, instrument calibration and highlight the observations from the rocket flight campaigns. I will focus on the coordinated microflare observations with Hinode/XRT and SDO/AIA and discuss the science enabled by the study of small scale energy releases in solar corona. This is the first time that this is done for a flare with FOXSI, the only direct focusing solar HXR instrument. The Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) experiment aims to constrain the frequency of heating in solar corona, by observing the Sun in soft X-rays from 0.5 to 2.0 keV. I will briefly summarize the novel design of MaGIXS instrument, which is undergoing flight calibration and scheduled for mid-2020. In this presentation, I will highlight my role in these two missions and share my experiences and lessons.

Astrochemistry 2019 - Where we stand?

Date: 2020-02-07
Speaker: Dr. Bhalamurugan Sivaraman
Venue: 113/114 - Thaltej seminar room

Abstract

Mars Environment Chamber: Design and Development

Date: 2020-02-07
Speaker: Dr. Deepak Singh
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The solar energy budget impacts various physical processes on the planet, and determines the state of the climate of a planet. The planetary albedo plays an important and significant role in impacting the solar energy budget. The Mars Environmental Chamber (MEC) is being set-up to create a controlled Mars environment, and determine the reflectance spectrum of both CO2 and H2O ice (for various possible scenarios of Mars) with high spectral resolution. Design, fabrication, and assembly of MEC have been completed. Currently, the integrity of the chamber with a pumping system is being tested, and the design and development of a thermal plate/sample holder within the current set-up is going on. Later, the UV and NIR spectrometer would be integrated with the chamber for spectral measurements. The derived spectrum (across the UV, visible and near-IR wavelength range) would be useful to quantify the impact of the albedo feedback on Martian climate.

Study of Paleo Marine Nitrogen cycle using Nitrogen isotopes

Date: 2020-02-04
Speaker: Mr. Deepak Kumar Rai
Venue: Ground Floor Lecture Hall

Abstract

Dinitrogen (N-2) gas is the most abundant form of Nitrogen in the Oceans. Still, most of the organisms cannot utilize it in this form. It first has to be converted to a reactive form by N-fixing bacteria. The fixed N inventory is primarily controlled by principal source (N-2 fixation) and sink (denitrification), both of these processes are mediated by marine organisms. So, the oceanic nitrogen budget provides a critical test case in the broader effort to understand the stabilizing environmental feedbacks on the Earth’s surface. However, it is difficult to quantify, based on temporally and spatially limited modern observations. Fortunately, geological archives have recorded past events those approximate large-scale experiments in which the oceanic N budget responds to naturally imposed forcing. In this talk, I will discuss how nitrogen isotopes are used for studying the palaeo marine nitrogen cycle.

Development of a Confined Circular-cum-parallel Ribbon Flare and associated Pre-flare Activity

Date: 2020-01-31
Speaker: Ms. Pooja Setia
Venue: USO Seminar Hall

Abstract

Heterogeneous chemistry in the Martian atmosphere

Date: 2020-01-31
Speaker: Dr. Ashimananda Modak
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Literature suggests that the HOx (H, OH and HO2) and Ox (O+O3), though found in trace amounts in the atmosphere of Mars, play an important role in the photochemistry and stability of the CO2 dominated atmosphere. Along with these trace gases, suspended dust particles affect not only the radiative budget of the atmosphere, but can play an important role in the photochemistry. Our aim is to understand the heterogeneous processes occurring in the Martian atmosphere. In a heterogeneous process, particles (for example dust) provide a surface for the sink of gaseous species. In this talk, I will present our study on the quantitative effect of heterogeneous processes on the Ox and HOx species of the Martian atmosphere, carried out using a one dimensional chemical model developed by us and also a three dimensional GCM.

Understanding the origin of the solar wind with Solar Orbiter, DKIST and Aditya-L1

Date: 2020-01-30
Speaker: Dr. Giulio Del Zanna (University of Cambridge, UK)
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

One of the main science questions in solar physics is how and where the solar wind is originating and accelerates. Together with Parker's Solar Probe, the main upcoming ESA solar mission, Solar Orbiter, is tasked to address this science question. I will briefly describe the suite of remote-sensing instruments (in particular the EUI imager, the PHI magnetic imager, the SPICE spectrometer and the METIS coronagraph) built to support the in-situ ones, to help locating the source regions of the solar wind. I will then briefly describe the DKIST near-infrared (NIR) coronagraph. DKIST is the first large-scale solar telescope providing unprecedented observations of near-infrared forbidden lines in the outer corona, to measure magnetic fields, line widths, densities etc. Together with the Proba-3 and the VELC coronagraph, on board Aditya-L1, the first major Indian mission to study the Sun, they will provide important information about the outer corona, in synergy with the Solar Orbiter observations. I will describe the complexities and advantages in using the NIR lines to measure densities, chemical abundances and temperatures.

Effect of Monsoon Intra-seasonal Oscillation on the rain isotope variability in northern Bay of Bengal

Date: 2020-01-28
Speaker: Prof. S.K. Bhattacharya
Venue: Ground Floor Lecture Hall

Abstract

Monsoon Intra Seasonal Oscillation (MISO) represents semi-periodic occurrence of rainfall spells over India during summer associated with large-scale movement of wind and clouds connecting convection and circulation, identified by northward propagation of Outgoing Long wave Radiation flux anomaly. The connection of MISO with the hydrological cycle has been explored here through stable oxygen and hydrogen isotope ratios in rainwater samples collected from two stations located near North Bay of Bengal during 2004-2014. The delta-18-O and delta-D values of the samples (total 202) have wide ranges: -18.2 to 2.8‰ and -132 to 28‰ (rel. to VSMOW) respectively. Out of 66 samples associated with 15 MISO events during this period, 46 have significantly low isotope ratios. These ratios are well correlated with the MISO propagation speed and cumulative rainfall over the Bay of Bengal. In addition, the isotope values also show a significant anti correlation (r2=0.88) with satellite derived stratiform rain fraction. The isotopic results were compared with the results obtained using an Isotope Enabled Global Spectral Model (IsoGSM). The model simulation reproduces the amplitude of variation in the observed values, but on average, the model values are higher in delta-18-O and delta-D by about 2‰ and 11‰ respectively and lower in d-excess by about 4.5‰ on average. It is proposed that the discrepancies in delta-18-O, delta-D and d-excess arise due to an overestimation (on average by 13%) of raindrop evaporation effect in the model.

Insights in to the development of Solar X-ray Monitor

Date: 2020-01-24
Speaker: Dr. M. Shanmugam
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Solar X-ray Monitor (XSM) is one of the scientific instruments onboard Chandrayaan-2 Orbiter. This instrument provides the solar X-ray flux for the estimation of global elemental composition of the Moon by the companion instrument CLASS. The high cadence and high energy resolution solar X-ray measurement by XSM is first of its kind and this data will be used for solar studies. XSM instrument is performing as expected and even exceeding the expectations in terms of its sensitivity compared to the existing solar flux measurements. In this seminar, I will discuss the insights in to the design aspects, how the XSM instrument configuration evolved and the performance measurements.

Role of active region filaments in triggering solar flares

Date: 2020-01-23
Speaker: Mr. Suraj Sahu
Venue: USO Seminar Hall

Abstract

Continuous-variable quantum repeaters based on the quantum scissors and mode multiplexing

Date: 2020-01-22
Speaker: Kaushik P. Seshadreesan
Venue: Ground Floor Lecture Hall, PRL Main Campus

Abstract

Quantum repeaters are indispensable for high-rate, long-distance quantum communications. The vision of a future quantum internet hinges strongly on realizing quantum repeaters in practice. Numerous repeaters have been proposed for discrete-variable (DV) single-photon-based quantum communications. Continuous variable (CV) encodings over the quadrature degrees of freedom of the electromagnetic field mode offer an attractive alternative. For example, unlike DV, CV transmission systems do not involve single-photon detectors and hence are easier to integrate with existing optical telecom systems. Yet, repeaters for CV have remained elusive. We present a novel quantum repeater scheme for CV entanglement distribution over a lossy bosonic channel that beats the direct transmission exponential rate-loss tradeoff. The scheme involves repeater nodes consisting of a) Einstein-Podolsky-Rosen entanglement sources that generate CV entanglement in the form of two-mode squeezed vacuum (TMSV) states, b) the quantum scissors operation to perform nondeterministic noiseless linear amplification of lossy TMSV states, c) a layer of switched, mode multiplexing inspired by second-generation DV repeaters, which is the key ingredient apart from probabilistic entanglement purification that makes DV repeaters work, and d) a non-Gaussian entanglement swap operation. We present our exact results on the rate-loss envelope achieved by the scheme.

Pancharatnam-Zak phase

Date: 2020-01-20
Speaker: Dr. Vivek Vyas
Venue: Ground Floor Lecture Hall, PRL Main Campus

Abstract

hree decades ago, in a celebrated work, Zak is credited to have found the geometric phase acquired by an electron in a one-dimensional periodic lattice as it traverses the energy band. It was found that such a geometric phase characterizes the topological state of the system and determines its electric polarization. Unfortunately, the expression given by Zak yields an arbitrary value for the geometric phase, which depends upon the choice of convention employed in expressing it. We rectify this gross error by providing a correct and consistent expression for such a geometric phase, which we call the Pancharatnam-Zak phase. In this talk we shall see that the Pancharatnam-Zak phase is a quintessentially geometric object, displaying gauge and reparametrization invariance, and correctly classifies the energy bands of the lattice. A filled band generalization of the Pancharatnam-Zak phase is also constructed and shall be discussed in the talk.

Design Aspects of Venus Radiation environment monitor (VeRad) and Peak Detector

Date: 2020-01-17
Speaker: Sushil Kumar
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Abstract : Venus Radiation environment monitor (VeRad) is an instrument selected for upcoming Venus orbiter mission with an objective to measure the high energy particle flux in the energy range of 100 KeV to 100 MeV which will help in understanding the effect of interaction of these particles on Venus atmosphere. In this presentation, I will be discussing about design aspects of VeRad. In addition to this, I will also be discussing about the design aspects of the in-house developed Peak Detector. Peak detector is an important part of a spectrometer design where measurement of peak amplitude of incoming voltage signal is measured and is kept on hold up to the time required for ADC. This peak amplitude indirectly corresponds to the energy information of the incident radiation.

QBO, ENSO and Solar Cycle Effects in Short-term Non-migrating Tidal Variability on Planetary Wave Timescales from SABER - An Information-Theoretic Approach

Date: 2020-01-13
Speaker: Ms. Komal Kumari
Venue: Ground Floor Lecture Hall, PRL

Abstract

Earth’s atmosphere supports a variety of internal wave motion which are responsible for spatio-temporal changes in temperature, winds, density, and chemical constituents. One of the most striking dynamical features of the upper atmosphere (i.e. mesosphere and lower thermosphere [MLT], 50-120 km) are “Atmospheric Tides”. In particular, the eastward-propagating non-migrating diurnal tide with zonal wave number 3 (DE3), originating from tropical deep convection, introduces a large longitudinal and local time variability in temperature, wind and density in the MLT region. The DE3 is thus a key to understanding how tropospheric weather influences space weather. However, DE3 short-term tidal variability is not well understood and part of the motivation for constellation missions. Single satellites such as TIMED nevertheless provide a pathway to identify multi-timescale tidal variability from days to years. We are utilizing 16 years of SABER (an instrument onboard TIMED satellite) DE3 tidal deconvolution diagnostics that provides a unique opportunity to investigate interannual changes in short-term tidal variability on various planetary wave time scales. The approach is based on information-theoretic techniques using Bayesian statistics, time dependent probability density functions and Kullback-Leibler divergence followed by multiple linear regression analysis. The statistically significant response to the inter-annual changes in short-term DE3 variability on planetary wave timescales with emphasis on 10-day wave associated with the quasi-biennial oscillation (QBO), El Niño-Southern Oscillation (ENSO) and solar cycle and their physical significance in relation to SABER 10-day wave diagnostics will be discussed in detail.

Chondrules : noble gases and nitrogen isotopic studies

Date: 2020-01-10
Speaker: Ramakant R. Mahajan
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Abstract : Chondrules are the major constituents of chondritic meteorites. They are one of the early solar system objects, thus provide information of processes happened at that epoch. Noble gas isotopic studied in chondrules gives an important information such as homogeneity/heterogeneity of noble gas isotopic ratios in the solar nebula. Constraining the gas composition in solar nebula (as in the formed of trapped gases in chondrules) is one of the main objective of chondrule study. Exposure before compaction is another aspects in case of chondrules, to determine their formation scenario. In this talk literature survey will be discussed alongwith new initiative.

Novel source of photon pairs for long-distance quantum communication

Date: 2020-01-10
Speaker: Dr. Shashi Prabhakar
Venue: Ground Floor Lecture Hall, PRL Main Campus

Abstract

Quantum technology is a fast-growing field of physics and engineering, which utilizes fundamental properties of quantum mechanics to enable new applications such as long-distance secure communication and metrology with sensitivity beyond classical limits. Currently, these technologies are available at visible, near-infrared (NIR) and telecom wavelengths but are strongly underdeveloped at longer wavelengths. There is a growing interest to deliver sources and detectors operating in the infrared, for various applications such as daylight satellite-to-ground and satellite-to-satellite based quantum communications, and future interferometric gravitational waves detection in LIGO experiments. In this talk, I am going to present the generation and characterization of a pulsed spontaneous parametric down-conversion photon pair source at 2.080 μm. The characterization includes the efficiency estimation of the crystal, coincidence-to-accidental ratio determination, estimation of quantum efficiency of single photon detectors at 2.080 μm, the two photon Hong-Ou-Mandel interference, and polarization entanglement

Sample Acquisition through Core drilling for Planetary Remote Sensing Laboratory Studies

Date: 2020-01-03
Speaker: Abhishek Verma
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Abstract : Sample acquisition for laboratory studies through sample return missions will play a pivotal role in future planetary exploration missions. Obtaining samples through core drilling is scientifically very important but technically equally challenging. In this seminar, I will be discussing the basic principles of core drilling and the challenges involved in the development of a suitable system for automated coring of planetary surfaces and their terrestrial analogues. Details of a few existing planetary core drilling systems and experiments will be described in detail.

On the Prediction of Magnetic Field Vectors of Interplanetary Coronal Mass Ejections

Date: 2020-01-01
Speaker: Ranadeep Sarkar, ,

Abstract

Coronal mass ejections (CMEs) are powerful expulsions of gigantic clouds containing magnetized plasma that routinely erupt from the Sun and propagate out through the solar system. When such an eruption is directed toward the Earth with high speed and has a southward component of the magnetic field (Bz), an intense magnetic storm occurs upon the impact of the CME on Earth’s magnetosphere. The storm can occur when the CME’s interplanetary flux rope (FR) and/or the sheath between the FR and the associated shock has southward Bz. Therefore, a prior knowledge of the strength and orientation of the magnetic field embedded in the FR is required in order to forecast the severity of geomagnetic storms caused by CMEs. We have developed an observationally constrained analytical model, the INterplanetary Flux Rope Simulator (INFROS), for predicting the magnetic-field vectors of interplanetary coronal mass ejections (ICMEs). The main architecture of INFROS involves using the near-Sun flux rope properties obtained from the observational parameters that are evolved through the model in order to estimate the magnetic field vectors of ICMEs at any heliocentric distance. As a proof of concept, we validate INFROS for an Earth-impacting CME which occurred on 2013 April 11. The predicted magnetic field profiles of the associated ICME show good agreement with those observed by the in-situ spacecraft, namely, WIND. In the talk, I will present these results obtained from INFROS model and its implication towards the space-weather forecasting. In addition, the INFROS model validation for an ICME event which was sequentially observed by the in-situ spacecraft, namely, MESSENGER at ≈ 0.45 AU and the STEREO-B at 1 AU will also be discussed. INFROS shows promising results in near real time which could prove to be an useful space-weather forecasting tool compared to the time-consuming and computationally expensive MHD models.

2019

Glaciation in the Late Amazonian Period of Mars: New Reports and Ongoing Work

Date: 2019-12-27
Speaker: Rishitosh K. Sinha
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Mars is a glaciated planet. It has preserved late amazonian aged (within past ~1 Ga) landforms on its surface whose morphological and topographic characteristics closely resemble terrestrial ice-related flow features. Some of the recent studies have reported glaciation on Mars to have occurred in polyphase thereby suggesting widespread glaciation in the timescales of past few million years, which is much younger than previously thought. In addition, other studies have also reported first evidence of an ancient glacial landscape on Mars at ~3.6 Ga. These studies have major implications for understanding the paleoclimate of Mars as earlier it has been shown that Mars glaciation was active during the past ~1 Ga to 100 Ma. I will discuss some of these previous reports during the seminar. Further, I will discuss some of our recent observations from a region that have revealed Mars glaciation to be very extensive and erosive in nature than previously thought.

Sparse star clusters and photometric metallicity maps of the Magellanic Clouds

Date: 2019-12-24
Speaker: Dr. Samyaday Choudhury (Macquarie University, Sydney, Australia)
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

I will present our studies directed towards two frontiers in the Magellanic Clouds (MCs, the LMC & SMC), a pair of interacting galaxies near the Milky Way (MW) : (1) Sparse star clusters - Our work on sparse star clusters in the LMC is aimed to increase our understanding of such objects using deep Washington photometric data of 45 star clusters. The sizes and masses of these inconspicuous clusters emphasizes that the LMC has a significant population of clusters, which are similar to the open clusters in the Milky Way (MW). Motivated by the above finding, a larger team is looking into the low mass open cluster like systems in the LMC & SMC using existing large area surveys (e.g. OGLE III). (2) Radial metallicity gradient (MG): The spatial distribution of heavy metals within a galaxy is an important indicator of its evolution and interaction history. The MCs are perfect laboratories to investigate radial MGs in a different environment w.r.t the MW (in terms of gravitational potential & metallicity). We have created first of its kind high-spatial resolution metallicity map by combining large-area optical photometric surveys (MCPS and OGLE III) with spectroscopic data of Red-Giant-Branch stars. These maps reveal the metallicity trend across the inner ~ 5 and 2.5 deg. field region of the LMC and SMC respectively. The MG of the LMC is almost constant within the bar region and falls off beyond that, indicating an active bar in the past. Whereas, the presence of any MG in the SMC is still debatable, and requires spatially larger data set to make significant advances. Presently, we are using the VMC-VISTA survey (a near-infrared public survey by the ESO) to unravel the metallicity trend within the SMC, covering 2-3 times larger spatial area (bar and regions of interaction) compared to our previous studies.

Investigating the cosmological principle using large surveys

Date: 2019-12-19
Speaker: Prof. Ashok Singal (PRL Ahmedabad)
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

According to the cosmological principle (CP), the universe is homogeneous and isotropic, without any preferred directions. The cosmic microwave background radiation (CMBR) shows an isotropic distribution, except for a dipole anisotropy, ascribed to a solar system peculiar velocity. The NRAO VLA Sky Survey (NVSS), comprising 1.8 million radio sources, has shown a dipole asymmetry corresponding to a velocity ~4 times the CMBR value, a result confirmed later by many independent groups. Further, in the TIFR GMRT Sky Survey (TGSS), comprising 0.62 million sources, a very significant (>10 sigma) dipole anisotropy, amounting to a velocity ~10 times the CMBR value, is detected. However, the direction of motion in both cases has turned out to be along the CMBR dipole. More recently, a homogeneously selected DR12Q sample of 103245 distant quasars has shown a redshift excess along the CMBR dipole direction, implying a velocity ~6.5 times in a direction opposite to the CMBR dipole. Since the solar system peculiar velocity should not dependent upon the specific data or technique used to determine it, an obvious inference could be that the discrepancies in dipole anisotropies seen in different surveys indicate the presence of a preferred cosmic direction (axis!), violating the CP, a cornerstone of the modern cosmology.

Nitty Gritty of ambient particulate matter over Bhubaneswar: an upcoming Smart City on the eastern coast of India

Date: 2019-12-16
Speaker: Trupti Das
Venue: Ground Floor Lecture Hall, PRL

Abstract

C/2016 R2 (PAN-STARRS) : A TALE OF A UNIQUE COMET AND NATURAL LABORATORY

Date: 2019-12-13
Speaker: DR. RAGHURAM SUSARLA
Venue: Room 113/114, Thaltej Campus

Abstract

X-ray Relativistic Reflection & Testing Strong Gravity

Date: 2019-12-12
Speaker: Dr. Kishalay Choudhury (IUCAA Pune)
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The first part of the talk presents results on the first, well-structured systematic study on the most up-to-date relativistic X-ray reflection code relxill for the dimensionless spin (a∗) parameter of astrophysical black holes, with spectral analysis of high-) parameter of astrophysical black holes, with spectral analysis of high- quality simulated data, emphasizing on only unabsorbed relativistic smearing and the detector resolution with NuSTAR. Yields even at high signal and low background seem to be subjective to fitting biases and the treatment of data, when checked against a similar work from literature. Nevertheless, a∗) parameter of astrophysical black holes, with spectral analysis of high- > 0.8 seems to be best recovered under the averaged conditions. The second part jumps into utilizing the knowledge gained from the first half, testing Einstein’s strong gravity for the Kerr hypothesis in 4-dimensional spacetime around the supermassive black hole of the narrow-line Seyfert 1 galaxy Mrk 335 using the only available, high-signal Suzaku data for a low-reflection estimate with the initial release of the now-publicly- available non-Kerr extension to relxill (relxillnk), developed at the astrophysics group in Fudan University. Results tend to show weak constraints for a∗) parameter of astrophysical black holes, with spectral analysis of high- against two of the leading-order deformation parameters α13 and α22 of the Johannsen metric, recovering the Kerr metric at 1σ, and carry no weight or physicalvalidity on solutions deviating from the Kerr geometry. This has been confirmed with a later, more sophisticated MCMC error analysis of the data with more up-to-date code and grids to examine the persistence of spurious solutions. A hybrid model, however, has been proposed for the first time for a high-flux state in this AGN, even with fits using the Kerr base model.

Multi-scale physics of turbulence and magnetic reconnection in space plasmas

Date: 2019-12-12
Speaker: Dr. Kirit D. Makwana
Venue: Ground Floor Lecture Hall

Abstract

Turbulence and magnetic reconnection are ubiquitous phenomena in a variety of space plasmas. Turbulence involves transfer of energy from large to small scales via nonlinear interactions, for ex. in the solar wind. Magnetic reconnection involves conversion of magnetic energy to particle energy via change in magnetic topology, for ex. in Earth's magnetosphere. Plasmas at large scales can be described as a fluid in the magnetohydrodynamic (MHD) approach while at small scales a kinetic particle-in-cell (PIC) approach is needed to model the interactions of plasma particles with electromagnetic waves. I will describe these computational approaches and recent advances made by using them. We find that the rate of reconnection in large-scale solar magnetic flux tubes can still be dictated by small-scale kinetic physics, having implications for coronal dynamics and space weather. Turbulence coupled with large-scale current sheets can trigger explosive reconnection like in solar flares. Turbulence itself shows a rich multi-scale behavior with MHD simulations at large scales identifying a novel regime of low Mach number, compressively driven turbulence which is dominated by fast magnetosonic modes, having implications for cosmic ray transport. In PIC simulations of turbulence we identify kinetic scale current sheets which are also observed in the solar wind. These sheets accelerate particles by means of reconnection, having fundamental implications for plasma heating & particle acceleration in a variety of plasmas. I will present future challenges and opportunities in this field, including space missions.

Machine Learning and its Application in Remote Sensing Data Classification

Date: 2019-12-12
Speaker: Dr. Anil Kumar
Venue: USO Seminar Hall

Abstract

Atmospheric Chemistry and Dynamics over the Indian region: Modeling perspectives- Part 2

Date: 2019-12-09
Speaker: Dr. Narendra Ojha
Venue: Ground Floor Lecture Hall

Abstract

The changes in the air quality and climate are mediated through the atmospheric chemistry. Indian subcontinent is a vast geographical system with very diverse natural and anthropogenic processes leading to complexities at both spatial and temporal scales. In this talk, a brief overview of different atmospheric models (box, regional, and global) and their use for specific applications will be presented. I would focus on the results evaluating the performance of such models in reproducing the atmospheric chemistry over the Indian region. A few recent modeling applications pertinent to the stratosphere-troposphere exchange and air quality aspects will also be discussed.

Planetary Remote Sensing Laboratory: A New Facility at PRL Thaltej campus

Date: 2019-12-06
Speaker: Dr. Neeraj Srivastava
Venue: Room 113/114, Thaltej Campus

Abstract

Propagation of Coronal Mass Ejections during Solar Cycles 23 and 24

Date: 2019-12-05
Speaker: Dr. Syed Ibrahim
Venue: USO Seminar Hall

Abstract

Investigating Particle Acceleration in the Wolf-Rayet bubble G2.4+1.4

Date: 2019-12-05
Speaker: Ms. Prachi Prajapati (PRL Ahmedabad)
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The supersonic winds produced by massive stars carry a large amount of kinetic power. In numerous scenarios such winds have been proven to produce shocks in which relativistic particles are accelerated emitting nonthermal (NT) radiation. This seminar will be focused on the first detection of NT emission from a single stellar bubble, G2.4+1.4, associated with a WO-spectral type Wolf-Rayet star, WR 102. Based on the present literature, massive star WR 102 is the hottest star known today with the surface temperature of 200,000 K. Upgraded Giant Metrewave Radio Telescope (uGMRT) observations were carried out for this investigation. The fraction of the available kinetic wind power of stellar winds that is converted into cosmic-ray acceleration is estimated to be of the order of a few percent. This finding constitutes an observational breakthrough and gives new insight on the NT physical processes taking place in the environments of isolated massive stars. In particular, the results show that non-runaway isolated massive stars are capable of accelerating relativistic particles and are therefore confirmed as sources of Galactic cosmic rays.

Atmospheric Chemistry and Dynamics over the Indian region: Modeling perspectives

Date: 2019-12-02
Speaker: Dr. Narendra Ojha
Venue: Ground Floor Lecture Hall

Abstract

Instrumentation for lightning detection

Date: 2019-11-29
Speaker: Ms. Sonam Jitarwal
Venue: Room 113/114, Thaltej Campus

Abstract

Chalks, Cherts and Fish Clay, and their links to the fall of Dinosaurs

Date: 2019-11-26
Speaker: Dr. Vineet Goswami
Venue: Ground Floor Lecture Hall

Abstract

Challenges in the calibration of astronomical X-ray instruments

Date: 2019-11-22
Speaker: Dr. Sunil Chandra
Venue: Thaltej Seminar Room (113/114)

Abstract

The calibrations of X-ray instruments dedicated to astronomical studies comprise a number of challenging tasks. The poor knowledge of optics and detector parameters may end in surprisingly inaccurate scientific outcomes. I have been working for the Soft X-ray Telescope (SXT) aboard AstroSat for the last 5 years. Being part of the instrument team even before the launch, I have developed a level of understanding about the basic system parameters such as effective area of the system, charge transfer in-efficiency, detector background etc and changes in these with mission life. During this seminar I would like to share my experiences of various calibrations of SXT and also will update you with the current status of SXT calibration.

Entangled photons, nonlocality and Bell's inequality

Date: 2019-11-18
Speaker: Mr. Satyajeet Patil
Venue: Seminar Room 113/114 (Thaltej Campus)

Abstract

Starting from Einstein's paper ( Can Quantum-Mechanical Description of Physical Reality Be Considered Complete? 1935), I will explain, why Einstein concluded that the quantum theory to be incomplete using an example of a compound system which we now call as the entangled system and introduced the hidden variable theory in attempt to replace the quantum mechanics. Later, in 1964 John. S. Bell showed that the predictions of the hidden variable theory are incompatible with the predictions of quantum mechanics. Clauser and his colleagues generalized the inequality shown by Bell and formulated the new inequality known as Bell's inequality. Violation of this inequality gives an indication of the presence of nonlocal correlations (Quantum Entanglement) that exist between two subsystems.

Three-dimensional magnetic field structure of a flux emerging region in the solar atmosphere

Date: 2019-11-15
Speaker: Dr. Rahul Yadav
Venue: USO Seminar Hall

Abstract

We analyze high-resolution spectropolarimetric observations of a flux emerging region (FER) in order to understand its magnetic and kinematic structure. Our spectropolarimetric observations in the He I 1083.0 nm spectral region of a FER are recorded with GRIS at the 1.5 m aperture GREGOR telescope. A Milne-Eddington based inversion code was employed to extract the photospheric information of the Si I spectral line, whereas the He I triplet line was analyzed with the Hazel inversion code, which takes into account the joint action of the Hanle and the Zeeman effect. The spectropolarimetric analysis of Si I line displays a complex magnetic structure near the vicinity of FER. Moreover, we find supersonic downflows of 40 km/sec appears near the footpoints of loops connecting two pores of opposite polarity, whereas a strong upflows of 22 km/sec appears near the apex of the loops. Furthermore, non-force-free field extrapolations were performed separately at two layers in order to understand the magnetic field topology of the FER. We determine, using extrapolations from the photosphere and the observed chromospheric magnetic field, that the average formation height of the He triplet line is 2 Mm from the solar surface. The reconstructed loops using photospheric extrapolations along an arch filament system have a maximum height of 10.5 Mm from the solar surface with a foot-points separation of 19 Mm, whereas the loops reconstructed using chromospheric extrapolations are around 8.4 Mm high from the solar surface with a foot-point separation of 16 Mm at the chromospheric height. The magnetic topology in the FER suggests the presence of small-scale loops beneath the large loops. Under suitable conditions, due to magnetic reconnection, these loops can trigger various heating events in the vicinity of the FER.

Day to day variability of gravity waves and their relationship with nighttime phenomena

Date: 2019-11-15
Speaker: Mr. Subir Mandal
Venue: Ground Floor Lecture Hall

Abstract

Gravity waves (GWs) are omnipresent in the upper atmosphere and they redistribute the energy in the medium as they propagate away from their source region. They are known to play important roles in modifying various upper atmospheric phenomena. Conventionally, optical methods are used to study GWs. Recently, we have devised a methodology to derive daytime GW characteristics using radio technique (Digisonde). Earlier works have shown that the daytime upper atmosphere prepares the conditions conducive or otherwise for nighttime irregularities to occur. Several days of data have been analysed to understand the upper atmospheric behaviour over equatorial latitudes. We have attempted to address the issue of occurrence of nighttime plasma irregularities (i.e., ESF, Equatorial Spread F) with regard to daytime GW characteristics over equatorial location. A broad overview of the various factors in the daytime that affect ESF occurrence will be given and some new results with respect to GW characteristics on days with and without the occurrence of post sunset ESF will be presented in this seminar.

Quantitative textural analysis of HED meteorites: What it tells about Vestan Geology?

Date: 2019-11-15
Speaker: Dr. Biraja Prasad Das
Venue: Room 113/114, Thaltej Campus

Abstract

Calibration and Characterisation of ChaSTE

Date: 2019-11-08
Speaker: Mr. P. Kalyan Reddy
Venue: Room 113/114, Thaltej Campus

Abstract

Second and third order susceptibility QPM interaction in Ferroelectric crystals and Organic Multilayer thin films.

Date: 2019-11-08
Speaker: Dr. Pavan Kumar
Venue: Seminar Room 113/114, Thaltej campus

Abstract

We report the first realization of χ(3) QPM THG in isotropic polymer films with alternatingly deposited multilayers of a highly nonlinear organic material and a passive polymer material. The phase mismatch created in the highly nonlinear medium was compensated in the passive medium. We also could demonstrate fast and wide wavelength tuning of a ns-optical parametric oscillator (OPO) based on 3-segment PPLN device. The first segment generated the ultra-broadband signal and the idler bands and the third segment amplified the selected wavelengths of the ultra-broadband gain. This wavelength selection could be electro-optically (EO) controlled by applying a dc electric field to the middle segment.

"1.Post-IR IRSL dating of coastal dune ridges in Vaigai Prodelta Region, South-Eastern Tamil Nadu, India (20 minutes) 2. New OSL dates for Quaternary alluvial successions, Sellicks Creek, South Mount Lofty Ranges, Southern Australia (20 minutes)

Date: 2019-11-01
Speaker: Prof Debabrata Banerjee
Venue: Room 113/114, Thaltej Campus

Abstract

IRIS2: using representative profiles to invert IRIS Mg II h & k lines

Date: 2019-10-31
Speaker: Dr. Alberto Sainz Dalda, Bay Area Environmental Research Institute, CA USA
Venue: USO Seminar Hall

Abstract

IRIS2: using representative profiles to invert IRIS Mg II h & kline

Date: 2019-10-31
Speaker: Dr. Alberto Sainz Dalda
Venue: USO Seminar Hall

Abstract

The thermodynamics of the solar chromosphere and the transition region (TR) is critical for understanding how the solar corona is energized from the photosphere. The most common method to recover the stratified information in the solar atmosphere is through 'inversion codes' which employ an iterative algorithm to solve the radiative transfer equation for a given model atmosphere by minimizing the difference between the observed and synthetic spectra. Since 2013, NASA's Interface Region Imaging Spectrograph (IRIS) has been providing unprecedented observations of the solar atmosphere from the upper photosphere to the corona, with special attention to the chromosphere and the TR. IRIS is equipped with both spectral and imaging capabilities in several wavelengths spanning the far- and the near-UV domain. In this talk, I will present inversions of the Mg II h&k lines observed by IRIS using the STiC inversion code which considers non-LTE, partial redistribution, and plane-parallel geometry. The results from this code, while being comprehensive of the thermodynamic conditions in the chromosphere, are unfortunately, computationally intensive and expensive. An alternative approach is using the concept of the Representative Model Atmosphere with the STiC inversion code, called IRIS2. The foundation of this novel code is based on easy-to understand, easy-to-use, representative elements obtained with a basic machine learning technique, such as k-mean clustering. This allows us to obtain a depth-stratified model atmosphere from the upper photosphere to the chromosphere in a few CPU-minutes for any IRIS Mg II h&k data set. I will illustrate how the concepts behind this code can be applied to any spectro(polarimetric) data.

Accretion-Ejection Coupling in Black Holes

Date: 2019-10-21
Speaker: Mr. Arghajit Jana (Indian Centre for Space Physics, Kolkata)
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The coupling between accretion disk and jet is well known. Observationally, strong signatures of disk-jet connections have been seen for many black hole binaries. The nature and evolution of jets depend on accretion flows around black holes. Correlation between X-ray and radio fluxes are also visible, which indicate the coupling between accretion disk and jet. Here, we discuss about the observational evidences of the disk-jet connections in the two-component advective flow (TCAF) paradigm. With TCAF, we have separated the jet and accretion disk components from the observed X-ray. We have studied the properties of the X-ray jet for a few black holes and the results will be discussed in the seminar.

Oxygen and Carbon Isotopic Composition of the Living Symbiont bearing Benthic Foraminifera from different regions of the Andaman Reefs

Date: 2019-10-15
Speaker: Dr. M. Muruganantham
Venue: Ground Floor Lecture Hall

Abstract

Benthic foraminifera which hosts algal endosymbionts, grow to larger sizes than most other benthic protozoans and are often informally referred to as Larger Benthic Foraminifera (LBF). The LBF are important calcifiers, contributing substantially to reef sediments and carbon sequestration. The LBF grow slowly over periods of months to an year or more to reach diameters usually in excess of 1 mm and commonly >1 cm. They are long lived compared to most other shallow-dwelling foraminifera. Because they host symbiotic algae, they generally require very clear water conditions, especially those living at depths >20 m. With suitable light intensities and limited availability of dissolved inorganic nutrients (e.g., ammonia, nitrite, nitrate and phosphate), the photosynthetic algal symbionts can produce far more photosynthate (i.e., simple sugars and lipids) than inorganic nutrients available to allow algal growth. Instead, the algae excrete their excess photosynthate to the host, providing the host with energy for calcification and feeding, and the latter provides essential nutrients for growth of host and the algae. All these physiological process are generally not observed in the smaller benthic and planktonic foraminifers. The stable oxygen and carbon isotopic composition (δ18O and δ13C ) of different species of live symbiont bearing larger benthic foraminifera from different reef areas of Andaman Islands have been analysed. Processes regulating the isotopic composition of these LBF would be discussed in my presentation.

Entanglement duality in polarization and orbital angular momentum

Date: 2019-10-14
Speaker: Mr. Nijil Lal C.K.
Venue: Photonics group cubicles room, First floor, New building, Thaltej campus

Abstract

Indistinguishability is a profound feature in the quantum world. In order to meaningfully describe a bipartite entangled state of two identical, indistinguishable particles, at least two variables are required. One variable A is used to label the particles while the entangled is observed in another variable B ([A,B] = 0). Hence two identical particles can be shown to be entangled in one variable or the other depending upon which variable is being used to distinguish the photons. Thus just the distinguishability reveals the entanglement. This property is called entanglement duality. In this talk, I discuss about how the entanglement present in two independent variables (polarization and orbital angular momentum (OAM)) of a pair of indistinguishable photons gets revealed as they are separated in one of the variables.

Cold gas in AGN host galaxies

Date: 2019-10-10
Speaker: Dr. J.N.H.S. Aditya (PRL, Ahmedabad)
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Probing the distribution and kinematical properties of cold gas present in the vicinity of active galactic nuclei (AGN) is critical for assessing the nature of interactions between the AGN and its host galaxy, thereby for understanding the AGN-host galaxy co-evolution. Cold atomic gas (HI) present in the surroundings of AGN can be probed via HI 21 cm absorption, that is an efficient technique for observing systems at high redshifts, z > 0.3. Our earlier studies have established that samples of compact radio sources at high redshifts, z > 1.0, have a significantly low HI 21 cm absorption strength compared to samples at lower redshifts. We find that this discrepancy could be caused by multiple factors: (1) a redshift evolution in the AGN host galaxies, (2) a varied gas covering factor, (3) or a systematic bias in the AGN ultraviolet and/or radio luminosities. We use our recent uGMRT observations, and similar searches available the literature, with the aim to identify the dominant cause among the above, if any. In the talk I will discuss about our recent new detection of HI 21 cm absorption at the highest redshift to date, z = 3.53. The source has an ultraviolet luminosity of 1023 W/Hz, a cut-off above which all the neutral hydrogen in the host galaxy is expected to be completely ionized. Our detection of HI 21 cm absorption in this system is thus a contrary to this hypothesis. Finally, I will talk about the importance of near-IR spectroscopic observations to probe the cold molecular gas in the AGN host galaxies.

First result of MAVEN Langmuir Probe plasma density investigation inside the magnetic pile-up boundary of Mars.

Date: 2019-10-04
Speaker: Prof. S A Haider
Venue: Room 113/114, Thaltej Campus

Abstract

Geological assessment of Shackleton Crater at the lunar south pole: Potential EVA targets

Date: 2019-09-27
Speaker: Mr. Harish
Venue: Room 113/114, Thaltej Campus

Abstract

Atmospheric composition over South Asia: Model simulations versus observations

Date: 2019-09-23
Speaker: Ms. Lakhima Chutia
Venue: Ground Floor Lecture Hall

Abstract

Atmospheric composition over South Asia has been changing rapidly in response to anthropogenic activities as well as the changes in the land-use and climate over the region, however, systematic observations over different environments are sparse here. Modeling studies that could fill this gap also remain highly limited in this region. In this direction, a regional (WRF-Chem) and a global atmospheric chemistry model (CAMS) are used to investigate the distribution of trace gases over South Asian region. WRF-Chem results for O3, CO, NOx, and SO2 are seen to be in agreement with in situ observations showing the model’s ability in reproducing contrasting chemical environments across the Indian subcontinent. This model further reveals the western coast, eastern India and the Indo-Gangetic Plain as the regional hotspots of intense photochemistry in agreement with the satellite retrievals. Lower ratio of glyoxal to formaldehyde suggested dominant influences of the anthropogenic emissions on the distribution of Volatile Organic Compounds (VOCs) over the Indian subcontinent, except the northeastern region, where biogenic emissions played important role. Analysis of a long-term CAMS simulation reveals rise in SO2 until 2015 especially over the industrial regions related with power generation. SO2 trend additionally influenced the distribution of sulfate aerosols over this region which has implications for the regional climate.

The Martian Atmospheric Boundary Layer

Date: 2019-09-20
Speaker: Prof. Varun Sheel
Venue: Room 113/114, Thaltej Campus

Abstract

Long term study of the Sun using Kodaikanal Digitized data

Date: 2019-09-19
Speaker: Prof. Dipankar Banerjee
Venue: USO Seminar Hall

Abstract

Solar Physics at ARIES Nainital

Date: 2019-09-19
Speaker: Prof. Wahab Uddin
Venue: USO Seminar Hall

Abstract

Long term study of the Sun using Kodaikanal Digitized data

Date: 2019-09-19
Speaker: Prof. Dipankar Banerjee, Indian Institute of Astrophysics Bengaluru
Venue: USO Seminar Hall

Abstract

At the Kodaikanal (KKL) observatory we have four sets of data which consist of While light photoheliograms since 1904, the Ca-K line spectroheliograms since 1906, H-alpha spectroheliograms from 1912 to 1998, and Ca-K spectroheliograms of prominences from 1912 to 1998. All these data are collected with the same instruments with no change in their optics in the last 100 years. Thus, these uniform and contiguous images are extremely valuable to study the long term variations of the Sun over a century. We have recently digitized all these datasets and made them open to the global community through the portal https://kso.iiap.res.in. In this talk I will present a summary of recent science results from this digitized archive.

Chandrayaan 2 landing site: on the eve of historic landing of Vikram near the south pole region of the Moon

Date: 2019-09-06
Speaker: Mr. Rishitosh K. Sinha
Venue: Room 113/114, Thaltej Campus

Abstract

Mysteries in Error Propagation

Date: 2019-09-03
Speaker: Dr. Arvind Singh
Venue: Ground Floor Lecture Hall

Abstract

We often use “method of error propagation” to determine uncertainty (error) in a dependent variable from the measured uncertainty in the independent variables. Intuitional notion of error propagation in statistics suggests that random relative error in the dependent variable cannot be less than the sum of those in the dependent variable(s). In this talk, I shall explain that some functions, however, do not follow this notion of error propagation. I shall further explain and discuss the behaviour of such functions and their implication to earth science observations.

Model-independent Astrophysical Constraints on Leptophilic Dark Matter in the Framework of Tsallis Statistics

Date: 2019-08-23
Speaker: Atanu Guha
Venue: Theoretical Physics Seminar Room / 469

Abstract

I will discuss model-independent astrophysical constraints on leptophilic dark matter (DM), considering its thermal production in a supernova core and taking into account core temperature fluctuations within the framework of q-deformed Tsallis statistics. In an effective field theory approach, where the DM fermions interact with the Standard Model via dimension-six operators of either scalar-pseudoscalar, vector-axial vector, or tensor-axial tensor type, we obtain bounds on the effective cut-off scale Λ from supernova cooling and free-streaming of DM from supernova core, and from thermal relic density considerations, depending on the DM mass and the q-deformation parameter.

Magnetoconvective Flows and Waves in the Lower Solar Atmosphere

Date: 2019-08-22
Speaker: Dr. Sangeetha C R
Venue: USO Seminar Hall

Abstract

Investigation of Thermosphere-Ionosphere system using Optical and Radio techniques

Date: 2019-08-19
Speaker: Mr. Sovan Saha
Venue: Ground Floor Lecture Hall

Abstract

The low-latitude thermosphere-ionosphere system is influenced by the neutral and electrodynamic processes. These processes are affected by equatorial electrodynamics, neutral winds, plasma densities, etc., which show day-to-day, seasonal, solar activity dependency. Investigations of the upper atmospheric behaviour can be carried out by various remote sensing methods. These include measurement of the optical emissions that originate from the neutral species at different altitudes and the return echoes from the ionosphere of the radio waves transmitted through the radio wave sounding techniques. Conventionally, OI 630.0 nm nocturnal emissions which originate from an altitude of around 250 km are used as a tracer for the investigation of the upper atmospheric behaviour. We use large field of view measurements using a High Throughput Imaging Echelle Spectrograph (HiTIES) for these studies. HiTIES has been commissioned at PRL’s Optical Aeronomy Observatory in Gurushikhar, Mt. Abu (24.5° N, 72.7° E, 16° N Geomagnetic). Several interesting features in night time airglow intensity variations have been observed. Some of the initial results obtained from the analysis of these emissions and their plausible relation with the equatorial processes will be discussed.

Spectral study of X-ray binary MAXI J1659-152

Date: 2019-08-16
Speaker: Mr. Sandeep Kumar Rout (PRL, Ahmedabad)
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Black holes with a low mass star as a companion (LMXB), spend most of their life in quiescence. They become visible in the X-ray sky only during violent episodes of outbursts triggered by an instability in the accretion disk. Much of the information about black holes has been acquired by studying the emission from the accretion disk and its surrounding during these outbursts. In the seminar, I will present the results of a broad-band spectral analysis of an LMXB MAXI J1659-152 during its September 2010 outburst. One important highlight of this work is the unambiguous detection of a retrograde spin of the black hole. The possible implication of spin on the apparent faintness of some BHBs will also be discussed.

X-ray Polarisation in general, its measurements techniques and hard X-ray Spectro-polarimeter

Date: 2019-08-14
Speaker: Mr. Abhay Kumar (PRL, Ahmedabad)
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Polarisation is the fundamental property of light. Polarisation studies can help in verifying different models given for astrophysical systems like in AGN, GRBs, black-hole binaries etc. to explain their geometry, strength of magnetic field etc. It can help in understanding the environment, geometry and magnetic field in the astrophysical systems and will be able to get the more correct model. I will talk about the basics of polarisation, polarisation in X-ray and its different measurement technique. I will talk about what is the importance of hard X-ray polarimeter and my work on the hard X-ray Spectro-polarimeter.

Induced coherence with and without induced emission

Date: 2019-08-14
Speaker: Mr. Subith Kumar P M
Venue: Room no.:-06, Thaltej Campus

Abstract

Scattering vector vortex beams: A comparison with scalar vortex beams

Date: 2019-08-14
Speaker: Dr. Salla Gangi Reddy
Venue: Seminar Room 113/114 (Thaltej Campus)

Abstract

In this talk, I will discuss about the generation of vector vortex beams using polarization sensitive spatial light modulator along with their scattering. We compare the results with the scalar vortex beams.

Degana crater, Mars: Geologic records from Noachian to Amazonian period

Date: 2019-08-09
Speaker: Mr. Harish
Venue: Room 113/114, Thaltej Campus

Abstract

Coincidence Detection Protocol

Date: 2019-08-09
Speaker: Mr. Ayan Biswas
Venue: Seminar Room 113/114 (Thaltej Campus)

Abstract

In this presentation, we introduce a novel quantum key distribution protocol, coincidence detection quantum key distribution protocol (CD BB84-QKD). We show that in this protocol Poissonian nature of weak coherent pulses instead of posing a security risk can be used to the advantage for achieving secure key rate over a longer distance as compared to standard decoy state quantum key distribution. This protocol will also be able to track the presence of Eve (Eavesdropper) from the multi-photon (mainly consisting of two and three photons) coherent weak laser pulses. We show that, using this method the key rate can also be increased as some of the multi-photon pulses will contribute to the final key.

Probing reaction dynamics by interacting intense femtosecond pulses with molecules

Date: 2019-08-09
Speaker: Ms. Rituparna Das
Venue: Theoretical Physics Seminar Room / 469

Abstract

The interaction of intense femtosecond pulses with atoms and molecules gives rise to new phenomena like multiphoton ionization (MPI), above threshold ionization (ATI), and tunnelling ionization (TI). ATI has been well investigated both theoretically and experimentally in atoms, where an electron absorbs energy higher than the threshold energy required for it to be removed from the atom. Similar process has been predicted in molecules and it is called above threshold dissociation (ATD). In this case, a molecule absorbs energy higher than the threshold energy required for it to dissociate. The bond breaking and bond formation in time domain is not well studied as this process occurred in ultrafast timescale ranging from picosecond to femtosecond. In this seminar, I shall discuss these processes, in particular ATD, chemical control and the time-resolved dissociation reactions.

Orbital angular momentum state of light in classical and quantum domain

Date: 2019-08-08
Speaker: Ms. Sarika Mishra
Venue: Seminar Room 113/114 (Thaltej Campus)

Abstract

Light carrying orbital angular momentum (OAM) generally known as optical vortex, find many application in optical tweezers and optical communication. Unlike the polarization of light, which offers a two dimensional Hilbert space, the OAM of photon provide an infinite-dimensional Hilbert space. The higher dimensional OAM correlations realized using spontaneous parametric down-conversion (SPDC) process is generally restricted to a sub-space of single OAM. This is due to the pump carrying a single OAM value. Access to other OAM sub-space can be realized by pumping with the superposition of optical vortex beam. I also talk about the quantum nature of SPDC with Hong Ou Mandel interference.

Temporal & Altitudinal Variations of Equatorial Electrojet: Recent Results

Date: 2019-08-05
Speaker: Dr. Kuldeep Pandey
Venue: Ground Floor Lecture Hall

Abstract

Many characteristics including longitudinal and latitudinal variations of Equatorial Electrojet (EEJ) are already known. However, the temporal variations of EEJ during disturbed space-weather conditions and the difference in altitude of the peak EEJ current based on experiments (~105 km) and theoretical models (~100 km) are still not comprehensively understood by the community. Given this background, the recently obtained results on temporal and altitudinal variations of EEJ are important and will be presented in this talk.

Study of Impact Basins on the Moon: Implications for evolution of the Lunar crust

Date: 2019-08-02
Speaker: Ms. Tanu Singh
Venue: Room 113/114, Thaltej Campus

Abstract

Validation of Hard X-ray Off-axis polarization capability of Cadmium Zinc Telluride Detector

Date: 2019-08-01
Speaker: Ms. Aarthy Essakiappan (PRL, Ahmedabad)
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Ever since the launch of Uhuru in 1970, the field of X-ray astronomy has grown tremendously over the past five decades. Though X-ray imaging, spectroscopy and timing studies have vastly advanced both over soft and hard X-ray regimes, the field of X-ray polarimetry is still under explored due to the difficulties in measuring X-ray polarization. The prime reason is, measuring polarization requires a large number of photons from the source. In case of hard X-rays, there has been no focal plane polarimeters so far, and only open detectors have been used to detect polarization. Cadmium Zinc Telluride Imager (CZTI) is one of the five payloads on-board AstroSat which is capable of doing imaging and spectroscopy over 20 - 200 keV and is proven to measure on-axis polarization over 100 - 400 keV. Besides on-axis sources like Crab and Cygnus X-1, CZTI have been detecting Gamma Ray Bursts (GRBs), which by its isotropic nature occur from any random direction in the sky. This creates a great opportunity to measure Hard X-ray GRB polarization (for which very less reliable results exist so far) using CZTI. Hence it is important to validate that CZT detectors could be used as hard X-ray polarimeter for GRBs. In my talk I would present the work done using the QM of AstroSat CZTI at TIFR, complimented by Geant4 simulations to validate the off-axis polarization capability of CZT detectors

Molecular alignment using ultra-short laser pulses

Date: 2019-08-01
Speaker: Mr. Madhusudhan P
Venue: Theoretical Physics Seminar Room / 469

Abstract

Chasing the electron and nuclear dynamics in atoms and molecules will facilitate in controlling the process. Ultra-short femtosecond pulses have become the key tool for chasing the dynamics and also controlling the reaction dynamics. In polyatomic molecules, at certain energies Born-Oppenheimer approximations break down. These regions of interest (Conical Intersections) are rich in fundamental physics, which when explored not only gives the reaction dynamics but also can be used to explore the quantum mechanics at an experimental level. Probing the wave packet dynamics near conical intersection is not straight forward. We are going to align the molecules and probe the wave packet near conical intersection. In this seminar, I will be addressing the concept of Molecular alignment on a theoretical platform with computational tools and solve the Time Dependent Schrodinger Equation.

Non-separable states of light - generation and analysis

Date: 2019-08-01
Speaker: Mr. Satyajeet Patil
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

For an entangled state of two photons, the probability of detecting the two photons in a given state, cannot be written as the product of individual probabilities of each photon. This is known as non-separability. Non-separability is not only an intrinsic nature of the quantum system but classical light beam can also be shown to possess non-separability, albeit between different degrees of freedom. The classical analogy of quantum entanglement is studied using a laser light beam, which is prepared in a non-separable state of different degrees of freedom (polarization and orbital angular momentum). However, the analogy fails to produce effects of quantum nonlocality. It must be emphasized that Bell's inequality was introduced to measure nonlocal entanglement between two quantum systems. In the present talk, I will discuss classical and quantum non-separable states, their generation and analysis.

Development of FOSC Instrumentation for PRL Telescopes : Commissioning of MFOSC-P and Optical Design of MFOSC-EP

Date: 2019-07-31
Speaker: Mr. Vipin Kumar (PRL, Ahmedabad)
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

FOSC (Faint Object Spectrograph and Camera) series of instruments are one of the most general purpose instruments on optical telescopes around the world. Given their ability to do imaging, spectroscopy and polarimetry within a single optical chain, they are highly desired for any optical observatory. Mt. Abu Faint Object Spectrograph and Camera-Pathfinder (MFOSC-P) is one such instrument which has been recently developed and commissioned on PRL 1.2m telescope; while MFOSC-Echelle Polarimeter (MFOSC-EP) is the next instrument, currently under design, for upcoming PRL 2.5m telescope. In this talk, we shall discuss the development of MFOSC-P including its commissioning observations and some of the on-sky characterization results, showcasing the science capabilities of the instrument. In the latter part of the talk, we shall discuss the proposed specifications and optical design of next instrument-MFOSC-EP. While retaining the FOSC functionalities, MFOSC-EP also consists of an intermediate resolution spectro-polarimetry mode which makes it a highly versatile instrument for upcoming 2.5m telescope. We shall summarize our efforts to overcome some of the challenging design problems with its optical design and expected performance.

HgOH as a prospective candidate to search for new particle physics

Date: 2019-07-30
Speaker: Mr. RAMANUJ MITRA
Venue: Ground Floor Lecture Hall, PRL Main Campus

Abstract

It is assumed that an electron can also have finite electric dipole moment (EDM) as its another intrinsic property like its mass or charge. The EDM of an electron can arise due to simultaneous violations of parity (P) and time reversal (T) symmetries. However,its Standard Model predicted value differs by several orders compared to other models of elementary particle physics. Direct observation of EDM of a single electron is impractical. Therefore,atoms or molecules are used as a means of its detection. In this talk, I shall demonstrate the triatomic molecule HgOH as one of the most promising candidates for electron EDM experiment. In this context, I shall also discuss about roles of studying permanent electric dipole moment and static electric dipole polarizabilities of molecule.

Investigations on ionospheric processes over low latitudes during quiet and disturbed periods

Date: 2019-07-29
Speaker: Mr. Ankit Kumar
Venue: Ground Floor Lecture Hall

Abstract

Ionospheric plasma distribution in the F-region over low latitudes depends on various electrodynamics processes that occur over dip equatorial region. These processes depend on globally generated primary electric field in the ionosphere. In daytime, F-region plasma fountain, driven primarily by this primary electric field, distributes plasma over low latitudes. As a result, higher electron density (F region ionization crest region) is found over low latitudes instead of dip equatorial region (ionization trough region). As ionospheric electric field show day-to-day variability over the dip equatorial region, the plasma density over the ionization crest region also show day to day variability. Meridional wind also contributes to this variability. Further, the effects due to prompt and delayed electric fields and composition changes coming from high latitudes also change the ionization distribution over low latitudes. Based on observations obtained from a number of techniques, these aspects will be discussed in the present talk.

2018 giant outburst study of Be/X-ray binary pulsar 2S 1417-624

Date: 2019-07-29
Speaker: Ms. Shivangi Gupta (PRL, Ahmedabad)
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The accretion powered X-ray pulsars are rotating neutron stars that emit X-rays as a result of mass accretion from their optical companion. They are considered to be an ideal astrophysical laboratory to test the fundamental properties of matter under extreme conditions. During the process of accretion, the interaction between pulsar's magnetic field and accreted gas results in the formation of a column like structure onto the poles of neutron star that acts as the source of X-ray emissions. This accretion column has a complicated geometry, hosting numerous complex processes that shapes the broad-band continuum of these objects. In this talk, I will discuss about these mechanisms, emission beam patterns, and the properties of pulse profiles. A case study of the pulsar 2S 1417-624 during its recent outburst in 2018 and the implications of our study would also be presented in detail.

Solar flares in the context of filament eruptions

Date: 2019-07-26
Speaker: Mr. Suraj Sahu
Venue: USO Seminar Hall

Abstract

Microtextural and Mineralogical study of CM chondrites: Implications of Parent body processes

Date: 2019-07-26
Speaker: Ms. Shivani Baliyan
Venue: Room 113/114, Thaltej Campus

Abstract

Discovery of complex macroscale structures in shock processed biomolecules - Implications to the Origin of life

Date: 2019-07-26
Speaker: Mr Surendra Vikram Singh
Venue: Ground Floor Lecture Hall

Abstract

In 1950's, Miller's experiment on biomolecule (amino acids) synthesis from prebiotic soup revolutionized our understanding on the Origin of life. Carl Sagan et al., in 1970 showed shock processing of simple molecules (ammonia, methane, water etc..) was also a pathway to the formation of amino acids in extreme conditions. Later, since 2000, the astrochemical ices containing simple and complex (purine and pyrimidine) molecules subjected to UV and charged particle irradiation were reported to synthesize amino acids and even nucleobases. However, the fate of biomolecules subjected to extreme conditions are to-date least understood. Recently, we have overcome the experimental limitations and observed complex macroscale structures in shock processed biomolecules. The results suggest the thread like features, so far, reported in meteorites are rather assemblages of biomolecules. In this talk, I will cover our efforts to understand the fate of biomolecules in extreme conditions and the preliminary results.

Interstellar Polarisation: Grain alignment theories and polarisation study towards high opacity LDN clouds

Date: 2019-07-25
Speaker: Ms. Archita Rai (PRL, Ahmedabad)
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Interstellar polarisation at optical and near- infrared wavelength bands is thought to arise when light from the distant stars passes through the interstellar medium consisting of asymmetric dust grains aligned with the magnetic field. Different theories have been developed to explain the process of grain alignment. They depend upon the sizes of the grain particles, the refractive index of the grains and the wavelength of observations. A study of the wavelength dependence of polarisation gives us insight into these features for the interstellar medium. The talk will mainly focus on the theories dealing with interstellar polarization by light passing through aligned grains. Some results from an ongoing work on Lynds Dark Nebulae (LDN) would also be presented.

Study of Noachian aged Volcanic Province: Understanding the Early Geologic History of Mars

Date: 2019-07-19
Speaker: Ms. Alka Rani
Venue: Room 113/114, Thaltej Campus

Abstract

Search and characterization of relic radio galaxies in deep fields

Date: 2019-07-18
Speaker: Mr. Sushant Dutta (PRL, Ahmedabad)
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The typical morphology of a radio galaxy consists of a core, pair of jets, lobes and hot-spots. The phase of radio galaxy evolution after the jets have switched off, is referred as remnant phase. The remnant phase is not well understood due to fact that it is short-lived and only few relic radio galaxies are known. We, therefore, have tried to improve the statistics on radio galaxies that have ceased to be active, or are intermittently active. I shall talk about the search for relic radio galaxies in the VLA-VIMOS VLT Deep Survey (VLA-VVDS) field using deep multi-frequency radio observations.

Modelling the solar and stellar magnetic cycles.

Date: 2019-07-17
Speaker: Dr. Bidya Binay Karak (IIT, BHU)
Venue: Thaltej Seminar Room (113/114)

Abstract

The sun and many other low-main sequence stars have active magnetic fields. The solar magnetic field reverses its polarity in about 11 years, and sunspots are the regions of intense magnetic field seen on the solar surface. The number of sunspots varies cyclically with a period of about 11 years which is popularly known as the solar cycle. However, this cycle is not regular; it has variation within a cycle as well as cycle-to-cycle. In this presentation, I will highlight my contribution in explaining these irregular features of the magnetic cycles of the Sun and other stars. Magnetohydrodynamics (MHD) dynamo process is believed to be responsible for such variation. The fluctuations in the so-called Babcock-Leighton process in generating a poloidal field in the solar dynamo, primarily through the scatter in the sunspot tilt, produce variation in the poloidal field and eventually cause irregularities in the solar cycle. I will further highlight our effort in explaining the features in magnetic cycles in other slowly rotating stars.

Thermodynamic modeling of the inner cometary coma

Date: 2019-07-12
Speaker: Ms. Sana Ahmed
Venue: Room 113/114, Thaltej Campus

Abstract

X-ray studies of GHz-peaked-spectrum (GPS) radio galaxies

Date: 2019-07-11
Speaker: Mr. Abhijit Kayal
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The GHz-peaked-spectrum (GPS) radio sources, a subclass of radio galaxies, are characterized by a convex radio spectrum peaked around 1 GHz. GPS radio galaxies exhibit compact radio size (~ 10 - 1000 pc) and are believed to represent the early stage of radio galaxy evolution. X-ray studies of GPS sources can help us in understanding the nature of environment around AGN and conditions during early phase of AGN activity. We have carried out X-ray spectral modeling of a sample of GPS sources and found that their X-ray spectra are characterized either by absorbed power law with high column density, or relatively flatter power law with Fe K_alpha emission line of high equivalent width. Hence, we conclude that GPS sources reside in dense circumnuclear environment. In this talk I shall also emphasize the need of hard X-ray spectral studies of GPS sources.

Hydro-meteorological processes in southern India: Insights from stable isotopes in precipitation at Hyderabad

Date: 2019-07-09
Speaker: Mr. Harsh Oza
Venue: Ground Floor Lecture Hall

Abstract

Understanding hydro-meteorological processes in southern India is important because it governs the availability and distribution of water in this region. Most of the southern Indian states depends predominantly on precipitation for its water requirement. Hyderabad, located almost at the centre of the Indian peninsula, equidistant from both Arabian Sea and Bay of Bengal, makes it an interesting location to study hydro-meteorological processes such as northward extent of North East monsoon (which is known to bring significant rainfall in the state of Tamil Nadu), effect of locally derived moisture in the rain and seasonal variation in the contribution of various moisture sources. Also, Hyderabad experiences frequent extreme weather conditions such as heat waves, droughts, heavy rainfalls and floods superposed over climatological normal. Understanding of these processes is also important because it has significant political and socio-economic implications especially in the wake of recent water crises in southern India. Stable isotopes of oxygen and hydrogen can be used to trace various hydro-meteorological processes such as vapour source variations, rainout history, vapour recycling, post-precipitation modifications, cloud microphysical processes, etc. Considering this, 182 daily rainfall samples were collected from Hyderabad during 2008-11 as a part of IWIN national programme. The isotopic analysis of these samples in conjunction with ground-based and remotely sensed meteorological parameters will be discussed in this presentation. Also, the importance of isotopes in understanding extreme weather events will be discussed.

Seismic Emission Accompanying Solar Flares

Date: 2019-07-04
Speaker: Mr. Hirdesh Kumar
Venue: USO Seminar Hall

Abstract

Understanding spectral observations of the Sun using numerical simulations

Date: 2019-07-04
Speaker: Shanwlee Sow Mondal
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Spicules are the jets of cold plasma that are chromospheric in origin. Multiple high-resolution imaging and spectroscopic observations have revealed the ubiquitous presence of spicules, especially the type-II spicules, in the solar corona. Such observations have claimed that the spicules play an important role in providing mass and energy to the solar corona and also help in maintaining its million-degree Kelvin temperature. We numerically simulate the propagation of such cold jet in a gravitationally stratified coronal magnetic structure. The simulation shows the heating of the tip of the spicule to million degree Kelvin due to the shock formation. The analysis of the synthetic spectral lines, constructed from the simulation data, lead us to conclude that probably the spicules provide very less plasma to the solar corona.

Gully formation on Mars: Wet or Dry process?

Date: 2019-07-04
Speaker: Mr. Rishitosh Sinha
Venue: Room 113/114, Thaltej Campus

Abstract

Astrochemical ices and residues

Date: 2019-06-25
Speaker: Mr. Rahul K Kushwaha
Venue: Room no 006, Thaltej campus.

Abstract

Comet Wirtanen: Initial target of the Rosetta Mission

Date: 2019-06-24
Speaker: Dr. Kumar Venkatramani (PRL Ahmedabad)
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Comets carry a significant amount of pristine material from the early solar system and become relatively bright when they approach the Sun. They appear brighter if they pass close to the Earth. Such an occasion gives us an opportunity to follow and probe these objects in detail. One such close approach of a comet happened in December 2018. Comet 46P/Wirtanen, the initial target of the Rosetta mission, had its closest approach to Earth (considering all its previous and future apparitions) on 15th of December 2018, three days after its perihelion. This comet was spectroscopically monitored using the low resolution spectrograph LISA on the 1.2m telescope at Mount Abu. High resolution spectra of this comet were obtained at various epochs using the the Hanle-Echelle Spectrograph mounted on the 2m Himalayan Chandra Telescope in Hanle. The comet exhibited various molecular emission lines like C2, C3, CN, NH2 as seen in the low resolution spectra. Many of the ro-vibrational lines of these molecular species have been identified in the corresponding high-resolution spectra. Many of the lines remain unidentified, due to the lack of an exhaustive line lists of various emission lines in a comet spectrum. Although each comet's composition might be different, there is a general pattern in which these emissions arise in various comets originating from different cometary reservoirs. In order to study the behavior of a comet and the evolution of its molecular emissions, we need to monitor the comet, as it travels past its perihelion. Some of the results from the observations of comet 46P will be discussed in this talk.

Optically detected magnetic resonance spectroscopy of NV centers in diamond: A few experimental advancements

Date: 2019-06-21
Speaker: Tanmoy Chakraborty
Venue: Ground Floor Lecture Hall

Abstract

Fluorescent point-defect centers in diamond, especially nitrogen vacancy (NV) center in diamond, have been widely exploited as a potential solid state spin-qubit system which has significantly boosted up research on quantum technology. There is a constant effort on standardizing the experimental protocols to manipulate the NV spins in a controlled fashion. On the other hand, research works have been devoted on optimizing the preparation procedure which can produce defect centers with superior optical properties, controllable spin states and that can be prepared in a reproducible manner. Through this presentation we will demonstrate a few important experimental progresses both in the direction of optimizing of quantum controlled experiments, and spectroscopic characterization of NV centers which are suitable for applications in quantum technology. In addition, our ongoing experimental efforts to explore new quantum defect centers will also be discussed.

Application of Gold encapsulated Carbon Nano-Spheres (Au@CNS) as Gamma Ray Detectors and energy source in space satellites

Date: 2019-06-21
Speaker: Mr. Ramkumar P.R
Venue: Room 113/114, Thaltej Campus

Abstract

Evolution of the Solar System and the importance of studies of the minor bodies

Date: 2019-06-20
Speaker: Mr. Aravind K. (PRL Ahmedabad)
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Our Solar System evolved from various processes like, formation of Sun, accretion of matter in a protoplanetary disk to form solid planets, gas giant planets, ice giant planets, asteroids, comets, Trans-Neptunian objects etc. There are Solar System formation models which say that the giant planets were at much more closer distance to the Sun, during formation, than at present time. This shift in semi major axis of the orbits happened due to various chaotic processes like resonance capture and exchange of angular momentum with planetesimals. These processes created drastic changes resulting in the current orbits of the planets and confinement of the asteroid belt or various cometary reservoirs. The objects in the asteroid belt between Mars and Jupiter are rocky materials since they could not preserve ice at such close distance from Sun. Whereas, objects in the Kuiper belt or the Oort cloud were formed at larger distances due to which the molecules have been preserved in its pristine form. My talk will hence try to uncover some of the mysteries and theories behind the evolution of our Solar System and therein emphasize on the importance of studies of the Minor bodies.

Hard X-ray Optics for Focusing X-ray Telescope

Date: 2019-06-19
Speaker: Mr. Biswajit Mandal (PRL Ahmedabad)
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Focusing optics in hard X-rays (10-100 KeV) require multi-layer coatings. In this framework we are developing the hard X-ray mirrors based on RF Magnetron Sputtering technique. Hard X-ray mirrors consists of multilayer coatings with alternate layers of high Z and low Z materials with typical thickness of 10-100 Angstrom. Coatings with equal spacing are effective for discrete energies but the thickness of the layers can be varied over different layers to obtain broader energy range. Design of such dept requires optimization of coating materials, number of layers, their thicknesses, roughness etc. IMD is a widely used software for such optimization, however, being an IDL based GUI software, it has some limitations in terms of iterative scripting capabilities or complex fitting. In this context we have developed alternate implementation of the Fresnel formalism to calculate reflectivity of multi-layer coatings which can be used with the standard spectral fitting software such as ISIS or XSPEC. In this talk, I will give a broad overview of hard X-ray optics for focusing telescope and the technique to form the hard X-ray mirrors and theoretical modeling of the mirrors.

Nitrogen Fixation during Summer Monsoon in the Bay of Bengal

Date: 2019-06-04
Speaker: Mr. Himanshu Saxena
Venue: Ground Floor Lecture Hall

Abstract

Primary producers are the first link in the food chain. Their production (i.e., primary production) in oceans is limited by the availability of light and nutrients. Dominantly, it is the nutrient (primarily bioavailable nitrogen) that regulates the primary production. Various mechanisms are responsible for providing nutrients to the primary producers. N2 fixation is one such process for supplying bioavailable nitrogen required for the sustenance of primary producers. It has been found that the N2 fixation rates in the Arabian Sea are highest among other oceans. But the Bay of Bengal, north-eastern part of the Indian Ocean, is known for ‘no study’ of N2 fixation rates. Therefore, to contribute to the present knowledge of N2 fixation rates in the Indian Ocean and to know the contribution of fixed nitrogen by N2 fixers to the primary productivity, N2 fixation rates in the Bay of Bengal during summer monsoon were measured. In this seminar, I will be discussing the N2 fixation phenomenon and the potential role of summer monsoon on the N2 fixation in the Bay of Bengal.

Tracking of solar eruptive filaments and finding the temporal connection with associated flare-CME events

Date: 2019-06-03
Speaker: Mr. Suvadip Sinha
Venue: USO Seminar Hall

Abstract

X-ray Studies of Type 1 Active Galactic Nuclei

Date: 2019-05-31
Speaker: Ms. Neeraj Kumari (PRL, Ahmedabad)
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

An active galactic nucleus (AGN), as its name suggests, is a compact region at the center of a galaxy which outshines the rest of the galaxy. It is strongly believed that the central super massive black hole (mass range between 10^6-10^10 solar mass) accretes matter from its surrounding medium and converts the gravitational potential energy into radiation. These are the most luminous persistent sources found in the Universe which emit in the entire range of electromagnetic spectrum. AGNs are classified broadly into radio-quiet and radio-loud AGNs depending on their emission in radio. In this talk, I will give a broad overview of AGNs, specifically my area of interest, in this vast field. I will discuss about X-ray properties of Seyfert galaxies which generally fall under the category of radio-quiet AGNs. The UV/X-ray spectrum of a Seyfert galaxy exhibit the following features apart from power law continuum: A Compton hump above 10 keV, a broad/narrow Fe k-alpha line at 6.4 keV, a soft X-ray excess below ~1 keV and a big blue bump (BBB) in UV range. Although the origin of the soft excess is still unclear, there are different physical models which successfully explain soft excess in one or the other Seyfert galaxies and quasars. The X-ray spectrum of Seyfert galaxies also shows signature of warm absorbers. In this talk, I will discuss the current understanding on the origin of various spectral components.

Autonomous generation of three dimensional magnetic nulls

Date: 2019-05-21
Speaker: Ms. Sushree Sangeeta Nayak
Venue: USO Seminar Hall

Abstract

Investigation of a long duration X-ray flare on an active RS Cvn-type eclipsing binary SZ Psc

Date: 2019-05-16
Speaker: Dr. Subhjeet Karmakar (PRL, Ahmedabad)
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

In this talk, I will discuss about a long duration X-ray flare observed on an partial eclipsing RS CVn-type binary SZ Psc. The flare was detected by the Neil Gehrels Swift Observatory on 2015 January 15 simultaneously using BAT, XRT, and UVOT. The SZ Psc system consists of a spotted chromospherically active ptimary K1 IV subgiant and a less luminous inactive F8 V secondary companion. The primary subgiant is filling 80-90% of its Roche lobe. With a duration of >1.3 days, this flare is one of the longest duration X-ray flares ever observed. The exponential rise and decay time of the flares were derived to be 3.5 and 5.5 hr, respectively. The peak X-ray luminosity in 0.3-10 keV energy band reached to a value of 4.8 x 10^{33} erg s^{-1}, which is 89 times more than that of the observed minimum value. Spectral analysis indicates a presence of two-temperature corona (11 and 49 MK) near the secondary eclipse whereas at the flare peak the temperature is 258 MK. The peak stellar abundances were derived to be 0.7 times more than solar abundances, which is also 10 times more than that of the minimum abundance observed on SZ Psc. The flare energy estimated to be ~1.98 x 10^{36} erg, and it can also be categorized as a Superflare. The total magnetic field estimated to produce the flare is 1.5 kG. Such large magnetic field at the coronal height is probably due to the presence of extended convection zone of the sub-giant and the high rotational velocity of this tidally locked system.

Spectroscopic and photometric study of cool and evolved stars

Date: 2019-05-09
Speaker: Supriyo Ghosh
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The cool and evolved stars with low-to intermediate-mass (0.8–8 Msun) lie in the Red Giant Branch (RGB) and Asymptotic Giant Branch (AGB) in post-main-sequence evolutionary phase. Precise estimation of fundamental parameters of these stars is very important to characterize the stellar populations in the galactic and extra-galactic environments. The atmospheres of AGB stars are strongly affected by the radial pulsation, and therefore, the time-dependent spectroscopy provides the understanding of ongoing physical processes in its atmosphere. I shall talk about the precise estimation of fundamental parameters from dominant spectral features of K–M giants derived by constructing a new near-infrared (1.50–2.45 μm) spectral library of 72 K–M giants using TIRSPEC instrument on 2m HCT. We also derive new empirical correlations between fundamental parameters and 12CO bands strength and study their relative effectiveness for the estimation of parameters. The presentation focuses on the characterization of a red optical transient, which was found as an O-rich (C/O<1) Mira variable, and a poorly known OH/IR star, using long-term optical/near-infrared photometric and spectroscopic observations.

Observationally Constrained Analytical Model for Predicting Magnetic Field Vectors of ICMEs at 1 AU

Date: 2019-05-09
Speaker: Mr. Ranadeep Sarkar
Venue: USO Seminar Hall

Abstract

Accurate relativistic calculations of molecular properties relevant to the search for new physics beyond the Standard Model

Date: 2019-05-08
Speaker: Dr. Srinivasa Prasannaa V
Venue: Ground Floor Lecture Hall, PRL Main Campus

Abstract

The parity (P) and time reversal (T) violating electric dipole moment of the electron (eEDM) is an extremely important non-accelerator probe of particle physics, and is also relevant to our understanding of the matter-antimatter asymmetry in the universe. This particle physics property can obtained by measuring a shift in the energy of a molecule in some state due to the eEDM, and combining it with a quantity that can only be calculated using relativistic many-body theory, the effective electric field (Eeff). The eEDM has not yet been detected; the best upper bounds have been obtained using ThO, followed by HfF+ and YbF. Advances in experimental techniques, as well as search for better molecular candidates, therefore, become imperative to probe new physics. In this presentation, we shall discuss our work, where we propose mercury alkalis (HgLi, HgNa, and HgK) as promising eEDM candidates, based on both theoretical as well as experimental considerations. We find that these reasonably large values of Eeff, in combination with attractive experimental features, lead to estimated sensitivities of ~10-30 e-cm, which is an order of magnitude better than the current best candidate, ThO. We shall also discuss our results of our calculations on the triatomic system, YbOH, on which an experiment has just commenced.

Spectral and timing evolution of long spin-period X-ray pulsars : Case study of 4U 2206+54

Date: 2019-05-07
Speaker: Dr. Prahlad Epili
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

In the frame of traditional scenario of spin period evolution in accretion powered X-ray pulsars, the spin down of neutron star (NS) pulsations beyond ~500s is very rare. However there are a few slow X-ray pulsators residing in binary stellar systems that show pulsations of the order of ~1000’s of seconds. To begin with the evolution of such slow pulsations require a magnetar field strength (~10^14 Gauss) of the NS. In order to understand the such peculiar slow pulsations in X-ray pulsars, we have studied the the X-ray timing and spectral properties of one such long-period (i.e ~5550s pulsation) X-ray pulsar in 4U 2206+54 using our recently proposed Astrosat observations. The timing studies indicate that the pulsar is showing a recent spin-up trend after its prolonged spin-down episodes. Alongwith the associated spectral evaluation the discussion would include the spin-evolution of very slow pulsation accreting neutron stars in binary systems reminiscing as accreting magnetar candidates.

Photochemical age of an urban air mass: A study using measurements of volatile organic compounds (VOCs)

Date: 2019-05-06
Speaker: Ms. Nidhi Tripathi
Venue: Ground Floor Lecture Hall

Abstract

VOCs are ubiquitous trace constitutes of the Earth’s atmosphere. Despite their low concentrations, VOCs impact the Earth’s climate and air quality. VOCs control the oxidative capacity of the atmosphere due to fast reactivity with hydroxyl (OH) radicals and lead to the formation of secondary compounds such as ozone, oxygenated-VOCs (OVOCs) and SOA. VOCs are emitted from both natural and anthropogenic sources. The contributions of different primary and secondary sources to ambient OVOCs are highly variable due to complex emission and atmospheric processes. In the atmosphere, fresh emissions are subject to mixing with different air masses and complex photochemical processes leading to change in concentration and composition of trace gases. The “photochemical age” has been used as a reference to investigate the evolution and transformation of an air mass on the exposure to OH radicals. A pair of VOCs emitted from similar source but with different removal rates can be used to calculate the photochemical age of an air mass. The role of different primary and secondary sources of OVOCs such as acetone and acetaldehyde measured at the Delhi during winter season has been investigated.

Quantum information with structured light

Date: 2019-05-06
Speaker: Mr. Anindya Banerji
Venue: Seminar Room #113/114 (Thaltej Campus)

Abstract

Photons with orbital angular momentum can be used for encoding information beyond one bit per single photon. This provides a great resource for the study of various fundamental properties of nature as well as utilise these properties for carrying out certain quantum information tasks. Also, photons with orbital angular momentum represent higher dimensional quantum systems or qudits. In this talk, we will discuss the generation and entanglement of photons produced by spontaneous parametric down conversion in the orbital angular momentum basis. We will also discuss the possiblity of using orbital angular momentum of the photons along with polarization for generating hyper and hybrid entangled quantum states.

Meta-material based antennas

Date: 2019-05-03
Speaker: Dr. Trushit Upadhyaya
Venue: Room 113/114, Thaltej Campus

Abstract

Interaction of Essential Climate Variables and marine aerosols: impact on climate

Date: 2019-04-29
Speaker: Dr. Aditya Vaishya
Venue: Ground Floor Lecture Hall

Abstract

Marine aerosols emission budget greatly surpasses any other source of natural or anthropogenic aerosol emission budget. This is due to the fact that approximately 70% of the Earth’s surface is covered by the ocean. Given the fact that the ocean surface is dark and marine aerosols readily act as efficient CCN, cloud layers formed by, or modified by marine aerosols effectively act as mirrors, reflecting back to space part of incoming solar radiation thus modulating global radiation budget. Modulations in the marine aerosol physical, chemical, and optical properties on account of interactions by a select set of ‘Essential Climate Variables (ECV’s)’ may influence the properties, extent, and lifetime of marine haze and clouds. In the present talk I will discuss about interactions between a select set of ECV’s, including aerosols, and its influence and impact on marine aerosol physicochemical properties and radiation budget. Decade long measurements from a Global Atmosphere Watch observatory at the western periphery of Europe indicate significant changes in marine aerosol properties on account of changes in ocean surface biology. Also, under typical marine boundary layer humidity fields, it was observed that marine aerosols enriched with oceanic surface organics are optically less active. The parameterized hygroscopic growth of such aerosols reveals a dual state of hygroscopicity flipping from high-hygroscopicity to low-hygroscopicity as the organic volume fraction increases from below ~ 0.55 to above ~ 0.55. Such changes in marine aerosols have significant impact on Top of Atmosphere (TOA) direct radiative forcing (ΔF) by reducing the cooling contribution of marine aerosols by ~ 5.5 times compared to pure marine salt spray. Further, using multi-instrument coherent measurement of aerosols properties it was shown that difference in aerosol scattering properties are not just due to a change in aerosol chemical composition but also due to change in aerosol dominant size mode. A shift in dominant aerosol mode to lower sizes, due to organic matter enrichment of marine aerosols, resulted in increase of aerosol sub-micron scattering fraction by over 2.5 times. Combining the effects of changing chemistry and size modes, we show that cooling contribution of marine aerosols enriched in oceanic organics is suppressed over 30% under humidity fields associated with cloud base as compare to marine boundary layer humidity fields. The results presented here highlight a significant coupling between the marine biosphere and the direct radiative budget through alteration of marine aerosol chemical composition. The shift to smaller sizes is likely to significant increase the lifetime of the marine aerosols in the atmosphere, possibly extending the duration and impact of marine haze in the global climate system.

Meteoritic evidence of Superflares in early evolving Sun

Date: 2019-04-26
Speaker: Dr. Kuljeet K Marhas
Venue: Room 113/114, Thaltej Campus

Abstract

Solar flares from delta sunspots: Insights from a simulation

Date: 2019-04-22
Speaker: Dr. Piyali Chatterjee
Venue: USO Seminar Hall

Abstract

A comprehensive study of comet dust at different heliocentric distances for varying radiation pressure.

Date: 2019-04-18
Speaker: Dr. Prithish Halder
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The study of light scattering properties of comet dust aggregates (0.7μm ≤ RC ≤ 2.0μm) with a wide range of porosity (P = 0.59 to 0.98) has been carried out using the High-Performance Computation (HPC). The results indicate that, when the porosity of the aggregates decreases, keeping characteristic radius RC same for all structures, there is an enhancement in the negative polarization branch which is accompanied by a substantial increase in the anisotropies present in the material. At the exact back-scattering region, the anisotropies are found to be linearly correlated with the porosity of the aggregated structure. Dust in the interstellar medium manifests in the form of extinction and polarization of starlight. To study this, I had carried out polarization observations of the dark cloud CB26 using 1.04-meter telescope at ARIES, Nainital. It has been found that the local magnetic field of the cloud is almost aligned with the Galactic magnetic field. Additionally, the extinction map reveals the presence of an active central core and a second low dense core. The visual extinction of field stars background to CB26 is estimated from 2MASS and Gaia archives using the Near-Infrared Technique. Details of the above studies will be discussed in this seminar.

Use of Brown Carbon Spectra as a Tool to Understand Their Broader Composition and Characteristics: A Novel Approach

Date: 2019-04-09
Speaker: Dr. Neeraj Rasotgi
Venue: Ground Floor Lecture Hall

Abstract

SHARAD Observations of Multiple Subsurface Reflections in Mangala Fossa Region, Mars

Date: 2019-03-29
Speaker: Mr. Rajiv R. Bharti
Venue: Room 113, Thaltej Campus

Abstract

Multi-wavelength Investigations of Magnetic Reconnection, Triggering and Stability of Solar Eruptions

Date: 2019-03-28
Speaker: Dr. Navin Chandra Joshi
Venue: USO Seminar Hall

Abstract

MSTIDs and their role in the mid and low latitude coupling processes

Date: 2019-03-25
Speaker: Dr. Sivakandan M.
Venue: Ground Floor Lecture Hall

Abstract

In contrary to the equatorial ionospheric irregularities which are generated by the Generalised Rayleigh-Tailor instability (GRT), it is believed that nighttime medium scale traveling ionospheric disturbances (MSTIDs) are generated in the mid-latitude ionosphere by Perkins instability. The unique feature of the nighttime MSTID is that its phase fronts are aligned in the north-west to south-east direction and propagates towards the equator. The equatorward propagation of the MSITDs is primarily controlled by the existence of the crest region of equatorial ionization anomaly (EIA) around ~15-20o Geomagnetic latitude. Furthermore, there are studies that suggest that the MSITDs can act as a seed perturbation for the equatorial plasma bubbles (EPB), particularly during solar minimum period when their ingression into low latitudes is deep in latitudes. There are studies that also brought out the interaction of MSTID and equatorial plasma bubbles (EPB). Therefore, MSTIDs are not only capable of providing seed perturbations but can directly interact with the EPBs. However, the background conditions that will determine the degree of interactions are not understood comprehensively till date. In the present talk, some insights about the MSTIDs characteristics and possible background condition for the low latitude propagation will be discussed.

The Radiation Belt Revolution

Date: 2019-03-22
Speaker: Dr. G. D. Reeves
Venue: Ground Floor Lecture Hall

Abstract

The discovery of the Earth’s radiation belts in 1958 was the first discovery of the satellite era. Very quickly after that, theories were developed that completely explained the observed structure and dynamics of the radiation belts. This “textbook” view persisted until the early 1990’s when new observations started a revolution in thinking about the radiation belts. Observations from CRRES, Polar, LANL-GEO, GPS, SAMPEX and others showed our textbooks were incomplete or even wrong - a gap in understanding that led to the Van Allen Probes mission. Since 2012 Van Allen Probes and other missions have fundamentally changed our understanding of the radiation belts while, at the same time, raising new questions that remain unanswered.

Daytime Studies of Earth's Upper Atmospheric Behavior Using Multiwavelength Imaging Echelle Spectrograph

Date: 2019-03-20
Speaker: Dr. Deepak Kumar Karan
Venue: USO Seminar Hall

Abstract

A new ANN based global 3D dimensional Ionospheric Model (ANNIM-3D) - Approach, Merits, Limitations and scope for improvements

Date: 2019-03-18
Speaker: Dr. S. Tulasiram
Venue: Ground Floor Lecture Hall

Abstract

Great efforts have already been made to model the terrestrial ionosphere, conventionally, by solving the conservation equations (physics based models) and fitting the large observational databases using predefined analytical functions (empirical models). While the both methods have their own advantages and limitations, we have adopted a new approach of using artificial neural networks to develop a global three dimensional ionospheric model by assimilating long term ionospheric observations from nearly two decades of ground based Digisonde, satellite based topside sounders and global positioning system – radio occultation (GPS-RO) measurements. The model predicted vertical electron density profiles have been validated with independent ground based incoherent scatter radar measurements at Jicamarca and Millstone Hill. Further, the model predictions are found to be quite promising with respect to ground-based Digisonde and topside satellite in-situ observations beside the well-established IRI-2016 model. The merits and limitations of this model and the scope for the potential improvements will be discussed.

The magnetic structure of a flux emerging region in the photosphere and the chromosphere.

Date: 2019-03-18
Speaker: Dr. Rahul Yadav
Venue: USO Seminar Hall

Abstract

The emerging flux region (EFR) at the solar surface shows a complex structure with magnetic bipolar (MBP) fields. The magnetic loops generated in MBPs connect the photosphere and the upper solar atmosphere. The interaction between the loops of opposite direction can trigger various explosive heating events located at different heights of the loop. Thus, their study is crucial in understanding the coupling of the solar atmosphere. An emerging magnetic loop was recorded by GRIS/GREGOR in 1083 nm spectral region, which includes a chromospheric He I triplet and a photospheric Si I line. In this talk, I will discuss how we can extract the magnetic field vector and other physical parameters of the magnetic canopies from the spectropolarimetric observations in He I 1083 nm.

The Development of MFOSC-P : Mount Abu Faint Object Spectrograph-Camera – Pathfinder on PRL 1.2m Telescope.

Date: 2019-03-15
Speaker: Dr. Mudit K. Srivastava
Venue: USO Seminar Hall

Abstract

Mt. Abu Faint Object Spectrograph and Camera-Pathfinder (MFOSC-P) is a fully in house developed instrument on PRL 1.2m telescope at Mt. Abu. MFOSC-P is designed to provide seeing limited imaging in Bessell's B,V, R and I filters over the field of view of ~5X5 arc-min^2. Slit limited resolutions of 2000, 1000 and 500 around 6500, 5200 and 6500 angstroms would be provided using three plane reflection gratings. The instrument has been designed fully in-house including its optical, mechanical, electronics motion control system and user's interface software, while commercially available off-the-shelf ANDOR 1KX1K CCD camera system is used as the detector. MFOSC-P has seen telescope first light in February 2019 very successfully and has been successfully verified for its imag/spectrum quality. We shall be discussing various design and development aspects of MFOSC-P in the talk.

Landing site for the Mars 2020 rover mission: New insights from remote sensing observations

Date: 2019-03-15
Speaker: Mr. Rishitosh Kumar Sinha
Venue: Room 113, Thaltej Campus

Abstract

Association of dawn-dusk asymmetry in the ring current with field-aligned currents under different space weather conditions

Date: 2019-03-11
Speaker: Dr. Sandeep Kumar
Venue: Ground Floor Lecture Hall

Abstract

Geomagnetic storms are the most important component of space weather studies. During a geomagnetic storm, global depressions in the horizontal component (H) of geomagnetic field are observed. This depression in H is mainly caused by the westward ring current encircling the Earth around 2-7 RE. The ring current is highly asymmetric during the main phase of the geomagnetic storm and a dawn-dusk asymmetry is observed in H components at low latitudes. This dawn-dusk asymmetry is generally attributed to the development of the partial ring current (PRC) which closes via region 2 field aligned currents (FACs) through auroral ionosphere. PRC is generally located in the dusk sector (1700-2100 MLT) and thus H variations on dusk side are more negative than the dawn side (0300-0700 MLT). The variation of dawn-dusk asymmetry under different solar wind interplanetary conditions and its association with FACs has been investigated. The results will be discussed during the talk.

Quantum walk of light in optical waveguides

Date: 2019-03-08
Speaker: Mr. Amit Rai
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Photonic waveguides have emerged as an ideal system for the study of quantum optical effects. In addition, they find interesting applications in quantum information science. I will describe my work on the transport and quantum walk of light in optical waveguides.

Where the energy during solar flare is released?

Date: 2019-03-07
Speaker: Dr. Susanta Kumar Bisoi
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

An outstanding question in solar physics is how and where the large amount of energy (up to 10^33 erg) is released during solar flare? The energy released during flare accelerates non-thermal electrons in solar corona which propagate along coronal magnetic field lines as electron beams and produce short-lived radio emission that appear as rapidly drifting structures in a radio dynamic spectra. They are known as Type III radio bursts. Such bursts are commonly associated with electron acceleration and flare energy release, particularly those Type III bursts identified in the decimetric frequency range (400-2000 MHz). Coronal X-ray and extreme Ultra-Violet observations have shown evidences of such electron acceleration. However, the observational evidence of the location of electron acceleration and so the flare energy release is still remained elusive. The ultra-high cadence radio dynamic imaging spectroscopy of Miangtu Spectra Radio Heliograph (MUSER), a radio interferometer located in China that operates in the decimetric frequency range of 400-2000 MHz, can be effectively used to solve this mystery. I will present in my talk MUSER imaging spectroscopy observations of such Type III decimetric bursts observed during flares with high spectral (25 MHz), spatial (1.3 to 50 arcsec) and ultra-high temporal (25 ms) resolution, and discuss how we can use the high resolution and high dynamic range radio imaging of Type III bursts to find the location of electron acceleration, and in turn, the location and nature of flare energy release.

The eruptive tempo of Deccan volcanism and Dinosaur extinction

Date: 2019-03-05
Speaker: Prof. J.S. Ray
Venue: Ground Floor Lecture Hall

Abstract

Investigation of gravity waves spectral characteristics using ground-based and satellite observations

Date: 2019-03-04
Speaker: Dr. Priyanka Ghosh
Venue: Ground Floor Lecture Hall

Abstract

Gravity waves (GWs) generated in the lower atmosphere are ubiquitous in nature. They significantly influence the local and global atmospheric dynamical and thermal structures through various dissipation processes. The perturbations in wind and temperature associated with upward-propagating GWs increase exponentially throughout their propagation from lower to higher atmosphere (due to decreasing atmospheric density). The amplified perturbations induce convective or shear instabilities at some altitude levels in the atmosphere where the GWs breaks or dissipates. Consequently, these GWs impart energy and momentum to the surroundings, while their power of wavenumber spectra and spectral slope gets saturated to preserve overall stability. Earlier studies reported that the GW power spectra of horizontal mesoscale velocity fluctuations exhibit universality in frequency, horizontal and vertical wavenumber (in the troposphere and lower stratosphere) regardless of any other parameters (e.g., topographical location, meteorological phenomenon, season, altitude, etc.). In this seminar, the GWs spectral characteristics obtained using ground-based and satellite observations will be discussed.

Design and Development of a Hybrid Laser-Induced Breakdown Spectroscopy (LIBS)-Raman System using Echelle Spectrograph for Material Characterization

Date: 2019-02-27
Speaker: Dr. Muhammed Shameem K. M
Venue: Ground Floor Lecture Hall

Abstract

A novel table-top Laser-induced breakdown spectroscopy (LIBS) and Raman spectroscopy hybrid system have been developed using a single pulsed Nd:YAG laser and a high-resolution ICCD coupled echelle spectrograph for more advanced material characterization. The complimentary elemental and molecular information of the analyte provides comprehensive information about the sample and help to omit the ambiguity while explain the inherent properties of the materials. The synergy between LIBS and Raman data has been successfully used for the analysis of clinical samples (kidney stones, teeth), plastics, chemicals, minerals, archeological samples, etc. The feasibility of collecting information from a remote distance has also been investigated using the combined measurements. The developed hyphenated remote LIBS-Raman system has been tested for security and mineralogical applications.

Role of Hall-MHD in coronal magnetic reconnection.

Date: 2019-02-26
Speaker: Ms. Kamlesh Bora
Venue: USO Seminar Hall

Abstract

Ultrafast tunable mid-infrared higher-order optical vortex source

Date: 2019-02-25
Speaker: Mr. Varun Sharma, SRF, PRL
Venue: 113/114 Thaltej Campus

Abstract

Development of coherent sources of laser radiation in mid-infrared (mid-IR) spectral domain is of major interest due to variety of applications ranging from remote sensing to optical communication. The advent of mid-IR sources, together with the spatial shaping into optical vortex profiles have led to interesting applications in the field of material lithography, studying chiral materials, microscopy etc. Optical vortices are beams with helical phase variation along propagation direction. Such beams have azimuthal phase variation represented by exp(ilθ), where l is the topological charge or order of the vortex. However, generation of optical vortices with wide wavelength coverage and high output power in ultrafast temporal domain requires exploration of alternative techniques. In this talk, I will present ultrafast optical parametric oscillators (OPOs) as a robust source of optical vortices in mid-IR spectral region. I will discuss challenges in designing such sources and performance of a vortex pumped picosecond OPO in mid-IR region up to 4035 nm.

Understanding supernovae diversity and exploring the rare and unusuals

Date: 2019-02-21
Speaker: Dr. Subhash Bose
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Supernovae (SNe) are among the most energetic and luminous events in the cosmos, and thus they are the important probe at extragalactic scales. SNe are produced from a wide range of progenitor and host environments, and so their observed properties are also diverse. Despite several decades of studies of these objects, various aspects are still poorly understood and highly debated. With the emergence of several all-sky and untargeted surveys, we are now able to find several extreme and unusual SNe which were previously unknown and challenges our present understanding of these objects. It is important to examine the rare and peculiar behaviors of these SNe to find clues to the missing links in our present understanding. With a growing sample of large number of observed SNe, It is also important to re-visit existing taxonomy schemes. In this context, I will talk about ASAS-SN survey and some of the rare and very unusual SNe discovered.

Application of Stable Isotopes in delineating recharge areas and identifying the sources of recharge

Date: 2019-02-21
Speaker: Prof. Gh. Jeelani
Venue: Ground Floor Lecture Hall

Abstract

The effect of ice albedo on Mars’ atmosphere through laboratory observations and modeling

Date: 2019-02-15
Speaker: Dr Deepak Singh
Venue: Room 113, Thaltej Campus

Abstract

Triggering and evolution of the largest solar flare of solar cycle 24

Date: 2019-02-13
Speaker: Mr. Prabir Kumar Mitra
Venue: USO Seminar Hall

Abstract

Geological and archaeological implications of drainage morpho–dynamics in NW Indo–Gangetic plains

Date: 2019-02-12
Speaker: Dr. Ajit Singh
Venue: Ground Floor Lecture Hall

Abstract

Indo–Gangetic plains is one of the largest alluvial plains adjacent to orogenic mountains. It comprises of alluvial sediment transported and deposited mainly by the Himalayan sourced antecedent rivers. This resulted in diverse geomorphic settings across the east–west strike of the Indo–Gangetic plains. The inter–basinal area between the Yamuna in east and the Sutlej in west is presently devoid of any major drainage except for the small ephemeral Ghaggar river. However earlier field based studies by geographers and later based on remote sensing approach have suggested presence of Ghaggar–Hakra paleochannel, in the Ghaggar plains, as a manifestation of a large river in the region. Pal et al. identified, few major paleochannels of Sutlej and Yamuna river and proposed that both these rivers were flowing into Ghaggar–Hakra paleochannel to form the large river. Also the largest concentration of Harappa civilisation is located near the Ghaggar–Hakra paleochannel. This led to a hypothesis that perennial Himalayan river flow sustained Harappan settlements in this region. However, such hypotheses have never been tested due to absence of data on subsurface stratigraphy, and provenance of buried sediment beneath the paleochannel. This seminar will deal with new results on shallow stratigraphy, sediment provenance, and chronology that respectively show fluvial architecture, Himalayan sources, and timing of fluvial activity of Ghaggar–Hakra paleochannel. Results will be presented from a new project focused to test the proposed connectivity of Yamuna catchment with the Ghaggar–Hakra paleochannel. This project is designed to understand the hydrology of Ghaggar-Hakra river system that possibly sustained the Harappan civilization.

Understanding the Geochemical Evolution of the Earth’s Mantle: Story from Carbonatites

Date: 2019-01-29
Speaker: Mr. Milan Kumar Mahala
Venue: Ground Floor Lecture Hall

Abstract

The Earth’s surface processes are expressions of its dynamic mantle. It has been established that despite billions of years of mantle convection, Earth’s mantle remains chemically heterogeneous. Therefore, understanding of the chemical evolution of the mantle and its implications for various processes in Earth through time requires study of various mantle derived products at different times in the Earth’s geologic past. Basalts are the obvious choice of such studies; however, to known the nature of fluids that are responsible for mobility of elements within the mantle one needs to study carbonatites. Carbonatites are magmatic rocks, rich in fluids and a whole host of trace elements, that carry and preserve the chemical information of the source regions more efficiently. In this seminar I will introduce the audience to these peculiar magmatic rocks and discuss their usefulness in tracing the mantle evolution through time.

Properties of Chromospheric Magnetic Field of Sunspots

Date: 2019-01-22
Speaker: Dr. Jayant Joshi
Venue: USO Seminar Hall

Abstract

The photospheric structure of magnetic field of sunspots has been studied extensively in the last few decades through Zeeman diagnostics of various magnetically sensitive spectral lines. Observation of magnetic field in the chromosphere is much more challenging than that in the photosphere. Therefore, the chromospheric magnetic field of sunspots has remained lesser explored. In addition to understanding three-dimensional structure of sunspots, knowledge of the chromospheric magnetic field is very essential for understating the small scale transient events in sunspots, e.g. ,penumbral micro-jets, transition region penumbral bright dots, and chromospheric oscillations. Using ground based telescopes, 1.5-meter GREGOR telescope and Swedish 1-meter Solar Telescope (SST), different aspects of chromospheric magnetic field of sunspots have been explored. In this seminar, I will focus on the fine-structure of magnetic field in a sunspot penumbra in the upper chromosphere. I will also present results from our recent study on the chromospheric magnetic field variations associated with umbralflashes and running penumbral waves.

Integrated photonics technology for quantum information

Date: 2019-01-11
Speaker: Dr. Jasleen Lugani
Venue: Room. 113/114 Thaltej

Abstract

Integrated optics platforms are widely explored nowadays for implementing different quantum information protocols and quantum optics experiments. In comparison to their bulk counterparts, on-chip circuits offer advantages in terms of scalability, reconfigurability and phase stability. In addition, integrated waveguides also offer higher non-linear interaction strengths and different degrees of freedom for quantum state preparation. With this motivation, several examples of on-chip linear optical networks based on different material platforms have been used to implement various quantum optics experiments such as bosonic transport simulations on silicon-on-insulator [1], universal linear optics circuit on doped silica [2] and so on. In this talk, I will focus on a few of such waveguide devices for state preparation and our recent work on an 8 x 8 reconfigurable transformation circuit which acts as an optical photonic processor based on Si3N4 waveguides [3]. The advantage of this platform compared to others is the unique combination of high index contrast, enabling a dense waveguide arrangement, ultra-low straight-propagation loss and offers spectrally wide transparency range. In addition, the device is reprogrammable, remotely controllable, and enables any 8x8 transformation. Our preliminary single photon experiments on this device, illustrates strong potential of this platform for quantum information processing protocols and quantum technologies. If time permits, I will also introduce my work on light-matter interaction in metastable helium vapours for optical memories and parametric amplification based on coherent population oscillations. [1] N.C. Harris, et al., "Quantum transport simulations in a programmable nanophotonic processor" Nature Photonics 11, 447 (2017). [2] J. Carolan et al., "Universal linear optics" Science 349 (6249), 711 (2015). [3] C. Taballione et al., "8 x 8 programmable quantum photonic processor based on silicon nitride waveguides", arXiv:1805.10999

History of Astronomy in TIFR and making of AstroSat mission

Date: 2019-01-10
Speaker: Prof. R.K. Manchanda
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

N/A

Isotopic characterization of Groundwaters of India: insights into hydrogeological processes

Date: 2019-01-01
Speaker: Mr. Amit Pandey
Venue: Ground Floor Lecture Hall

Abstract

Only 3% of the global water is fresh water, of which only 30% is groundwater (0.009% of total water on earth). In an agrarian country like India, where rainfall is erratic and unevenly distributed, groundwater becomes the important source of irrigation as well as domestic usage. Availability and quality of groundwater is adversely affected due to overexploitation, geogenic and anthropogenic contamination and climate change. While the adverse effects on groundwater, and the dependent economy and ecology, are obviously realised, the mechanism of underlying geohydrological processes is not so well understood. Hence, the knowledge about spatially variable geohydrological processes has become crucial not just from the academic perspective but in order to provide societally relevant information which can be useful in efficient water resource management in the field. In the above backdrop, I will pursue my Ph.D. research in the field of groundwater hydrology whereby I propose to use isotope characteristics of groundwater of first unconfined aquifer to answer some of the emergent scientific questions pertaining to geohydrological processes. In this talk, I would provide a broad outline and objectives of my future doctoral research work, major scientific questions to be addressed, challenges and limitations.

2018

Quarternary glaciation studies using terrestrial cosmogenic nuclides

Date: 2018-12-18
Speaker: Mr. Partha Sarathi Jena
Venue: Ground Floor Lecture Hall

Abstract

Advances in Himalayan glaciers have been found to be linked with regional factors, unlike glaciers from extratropical regions which are controlled by orbital forcing. Previous studies have demonstrated contrasting glaciation pattern in Himalayan region possibly as a result of the orography and climate of the region. Several researchers observed that advancement and retreat of the Himalayan glaciers is affected by the monsoonal or westerlies precipitation. In order to study the paleoclimate, it is a prominent approach to analyze Time, Duration and Extent of glaciation in the geological past. 10Be is a cosmogenic radionuclide produced by interaction of cosmic ray particles with materials in the earth’s atmosphere and surface. By using the production rate and concentration of 10Be in surface rocks samples, estimates of chronology of past glaciation cycles can be made. In this presentation, exposure age dating of glacially eroded rock surfaces and moraine boulders will be discussed along with a brief insight into the past glaciation studies in the Himalayan region using Terrestrial Cosmogenic Nuclide (TCN) Method

Advances and Challenges in Space Plasma Modelling and Its Application to Space Weather Forecasting

Date: 2018-12-18
Speaker: Dr. Bhargav Vaidya
Venue: USO Seminar Hall

Abstract

Numerical simulation, which provides a natural bridge between theory and observations, is an essential tool for understanding complex plasma behaviour. Space plasma modelling typically span a tremendous scale of densities and temperature with scales ranging ten orders of magnitude in space and time. Additionally, multiple processes developing at the electron, ion and global scales strongly interact with each other. For example, processes like supersonic shocks, magnetic reconnection and turbulence play a very crucial role at these different scales and significantly alter the structure of space plasma. These physical phenomena are also responsible for acceleration of particles to very high energies. I will describe our recent development of an hybrid framework with PLUTO code to study space and astrophysical plasmas at various scales. As a potential application to this novel framework, I will present some the very recent and ongoing work on space weather forecasting. Developing prediction models for space weather has lately come into tremendous focus within the space science community. The key ingredient to develop such a model requires a detailed understanding of the magnetic activities on the Sun, formation of CMEs and associated high energy particles, propagation of CME shocks through the heliosphere and finally its impact on Earth's magnetosphere. In this talk, I will review recent advances in developing a numerical framework for space weather forecasting. Further, I will also outline some of the challenges that the space plasma modelling community is facing today and in the future.

Dust Charging kinetics in a Plasma

Date: 2018-12-14
Speaker: Dr. Sanjay Kumar Mishra
Venue: Room no 113, Thaltej Campus

Abstract

Marine Heterotrophic Nitrogen Fixation

Date: 2018-12-11
Speaker: Mr. Himanshu Saxena
Venue: Ground Floor Lecture Hall

Abstract

The fixed nitrogen is the most important nutrient fuelling phytoplankton growth in the ocean. Thanks to the N2-fixers, a special group of marine plankton that are able to convert dissolved nitrogen gas into bioavailable nitrogen such as ammonium. Marine nitrogen-fixing cyanobacteria play a central role in the open-ocean microbial community. Once thought ocean to be dominated by cyanobacteria in the warm oceans, it is now clear that marine N2-fixing organisms in the ocean are more diverse, and are geographically more widespread than expected. In this talk, I will be discussing the types of N2 fixers and how they contribute to the nitrogen budget of the ocean. In addition, lack of knowledge about nitrogen fixation in the Indian Ocean will also be discussed.

Parametric source: Trends and applications

Date: 2018-12-10
Speaker: Dr. S. Chaitanya Kumar
Venue: Room No. 113/114, Thaltej

Abstract

Practical solid-state sources of tunable coherent radiation extending from the ultraviolet to mid-infrared can have an immense impact not only on the research and industry, but also on our daily life. In particular, mid-infrared wavelength range covering the molecular finger-print region is of great interest for variety of applications including spectroscopy and biomedicine. Nonlinear frequency conversion sources such as optical parametric oscillators have emerged as powerful tools, enabling access to these different spectral regions and are capable of providing broad and continuous wavelength coverage, operating in all time-scales from continuous-wave to ultrafast femtosecond regime. In this talk, I will present some of the recent advances in the development of parametric sources together with some interesting applications.

LA-ICPMS: Calibration Technique and Data Analysis

Date: 2018-12-07
Speaker: Ms.Garima Arora
Venue: Room no 113, Thaltej Campus

Abstract

Complex Evolution of Magnetic Helicity in Active Regions

Date: 2018-12-06
Speaker: Dr. B. Ravindra
Venue: USO Seminar Hall

Abstract

Active regions on the Sun emerge on different scales, latitudes and time of the solar activity. These active region magnetic fields are believed to be generated through dynamo action at the shear layer located beneath the convection zone. These magnetic fields are concentrated into flux tubes which rise through the convection zone and form bipolar sunspots at the photosphere. The simulations show that magnetic fields emerge from the photosphere with a twist. Some of the active regions show more twist than the others. The twists in the active regions are measured through a quantity called magnetic helicity. With the available long time sequence of magnetograms, several studies have been reported in the literature about the measure of helicity flux density in active region coronae. In this talk, I will discuss the components of helicity flux measured through the partitioning of the magnetograms into a set of unipolar regions; the methodology adapted for the magnetograms partitioning; the magnitude of the helicity flux components and its application to rotating and emerging sunspot regions.

Sources and sinks of nitrous oxide in the ecosystem

Date: 2018-12-04
Speaker: Mr. Mohammad Atif Khan
Venue: Ground Floor Lecture Hall

Abstract

Nitrous oxide is an undervalued but an important long-lived greenhouse gas and ozone-depleting entity, which has increased by almost 20 percent compared to the pre-industrial era, thus becoming a global concern. In this talk, the concepts of global warming, the greenhouse effect, and global emission rates of N2O from various reservoirs will be discussed. N2O production by different microbial pathways and factors influencing its emission in the terrestrial ecosystem will also be discussed. At last, the importance of the stable isotopic composition of N2O in identifying the processes responsible for its production and major sources will be introduced.

Quantification of contribution of biomass burning to the observed black carbon concentrations using FLEXPART

Date: 2018-12-03
Speaker: K. Renuka
Venue: Ground Floor Lecture Hall

Abstract

Black carbon is an atmospheric pollutant that comes from incomplete combustion of fossil and biomass fuels. It affects human health by causing cancer, respiratory diseases and cardiovascular dysfunctions. It also affects the earth’s climate by interacting with radiation either directly or indirectly. There exist large uncertainties in estimates of radiative forcing of BC due to uncertainty in emission fluxes and variations in optical properties for BC emitted from biomass burning. Using an emission inventory based on MODIS fire counts and a Lagrangian particle dispersion model we have quantified the contribution of biomass burning emissions to the observed BC concentrations at Ahmedabad. The results will be discussed in the seminar.

Global distribution of overlapping lobate deposits in gullies found on Mars

Date: 2018-11-30
Speaker: Mr Rishitosh Kumar Sinha
Venue: Room no 113, Thaltej Campus

Abstract

Solar Wind Density Turbulence from 2 to 45 Rsun

Date: 2018-11-28
Speaker: K. Sasikumar Raja
Venue: USO Seminar Hall

Abstract

Various types of remote sensing observations have been used so far to probe the weakly compressible density turbulence in the extended solar corona and solar wind. Using the angular broadening observations of radio celestial point like sources, we have studied various turbulent parameters in the solar wind: anisotropic broadening, amplitude of density turbulence, density fluctuations, proton heating rate and the dissipation scales. For this study, we used the observations of Gauribidanur radioheliograph, Very Large Array and other historical observations carried out during 1952-2017. In this talk, I will discuss, the way these parameters vary with heliocentric distance and the solar cycle. The newly launched Parker Solar Probe and upcoming Solar Orbiter missions are going to play a crucial role in understanding long standing mysteries of the solar wind. Apart from these, I will briefly discuss the CALLISTO spectrometer which we have recently installed at IISER Pune to monitor the transient radio emissions from the solar corona.

Strengthened Indian summer monsoon precipitation susceptibility linked to dust-induced ice cloud modifications

Date: 2018-11-19
Speaker: Piyushkumar N. Patel
Venue: Ground Floor Lecture Hall

Abstract

Most previous studies have focused on the impacts of anthropogenic aerosols on monsoon rainfall and variability. However, recent studies showed that only 25% contribution of global emissions are from anthropogenic aerosol, whereas natural dust sources globally account for 75% of emissions. A growing body of research has underscored the radiative impact of mineral dust in potentially influencing the Indian summer monsoon rainfall variability. However, the various mechanisms remain poorly understood especially from an dust-cloud-precipitation interaction perspective, which is among the largest sources of uncertainties in climate forcing. Additionally, the radiative forcing due to aerosol-ice cloud interactions (reported to be between -0.67 W m-2 and 0.70 W m-2), represents the largest source of uncertainty in climate forcing, which needs to be better understood and constrained. This demands improved sub-grid scale process-level understandings using precise, stable and long-term measurements of dust and ice-cloud properties at regional and global scales. In this context, 11-years of multi-satellite observations along with reanalysis data revealed a dust-induced microphysical-dynamical coupling leading to the deepening of ice-clouds and strengthening of precipitation susceptibility. Some of these results and their relevance to climate change will be discussed in this seminar.

Type II radio bursts, coronal mass ejections and geoeffectiveness

Date: 2018-11-16
Speaker: Dr. A. Shanmugaraju
Venue: USO Seminar Hall

Abstract

A BRIEF INTRODUCTION TO VENUS NEUTRAL AND ION MASS ANALYSER (VENIMA)

Date: 2018-11-16
Speaker: Mr Amogh Auknoor
Venue: Room no 113, Thaltej Campus

Abstract

Density turbulence in the solar wind using low frequency angular broadening observations

Date: 2018-11-15
Speaker: Dr. K. Sasikumar Raja
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Various remote sensing observations have been used so far to probe the weakly compressible density turbulence in the solar wind. Using the angular broadening observations of radio celestial point like sources, we have studied the various turbulent parameters in the solar wind: anisotropic broadening, amplitude of density turbulence, density fluctuations, proton heating rate and the dissipation scales. For this study, we used the observations of Gauribidanur radioheliograph, Very Large Array and other historical observations carried out during 1952-2017. In this talk, I will discuss, how these parameters vary with heliocentric distance range ~2-40 Rsun and the solar cycle. The newly launched Parker Solar Probe may provide valuable insights in understanding these long standing issues of the solar wind.

Mineral phase transformation: Earlier classical ideas to modern concepts

Date: 2018-11-13
Speaker: Dr. Alik Sundar Majumdar
Venue: Ground Floor Lecture Hall

Abstract

Most of our mineralogical concepts bear the legacy of material sciences where minerals are considered as materials and a "dry solid-state" mindset is applied in explaining mineralogical features. However, natural systems are not "dry" and "closed" rather it is commonly "wet" and "open". Following this, I will start the talk with little bit idea about the development of ideas on mineralogy, specially on mineral phase transformation to explain why are all the interpretations of processes in minerals and rocks dominated by “solid-state” mechanisms? Next, I will discuss the fundamentals of mineral stability diagram calculation using "equilibrium thermodynamics" in "dry" system, its pros and cons. Finally, I will focus on - (1) modern observations on mineral phase transformation from nano-scale perspective, (2) concept of "wet" system, non-equilibrium thermodynamics, and (3) the role of fluid on mineral phase transformation and deformation.

Nonlinear generation of ultrafast higher-order Poincare beams

Date: 2018-11-02
Speaker: Dr. Ravikiran Saripalli
Venue: Room No. 113/114, PRL Thaltej

Abstract

Light beams carrying both spin angular momentum (SAM) and orbital angular momentum (OAM) can be represented by mapping the total angular momentum onto a higher-order Poincare sphere. Due to their non-separable nature and infinite dimensionality in OAM degree of freedom, these beams have vast applications in optical communication. Thus it is highly beneficial to generate higher-order Poincare beams with large OAM order and at different wavelengths. However, the wavelength tunability is restricted in typical techniques to generate such beams which mainly rely on q-plates, spatial light modulators, or interferometric methods. The polarization dependence on phase matching condition makes it challenging to use nonlinear interactions of these beams to generate different wavelengths. In this talk, we present the nonlinear second harmonic generation of ultrafast, higher-order Poincare beams with large OAM orders (up to 24) at 405 nm wavelength.

Versatile Readout ASIC For Multi-Channel Large Area X-Ray Silicon Drift Detectors

Date: 2018-11-02
Speaker: Mr Nishant Singh
Venue: Room no 113, Thaltej Campus

Abstract

Gamma-ray emitting narrow-line seyfert 1 galaxies

Date: 2018-11-01
Speaker: Dr. C.S. Stalin (IIA, Bangaluru)
Venue: Thaltej Seminar Room (113/114)

Abstract

Not available

Report on the current radiocarbon measurements by PRL-AMS

Date: 2018-10-30
Speaker: Dr. M. G. Yadava
Venue: Ground Floor Lecture Hall

Abstract

AMS (Accelerator Mass Spectrometry) is nowadays a commonly adopted method for the measurement of natural radioisotopes having very low abundance such as radiocarbon. The greatest advantage that AMS radiocarbon dating has over conventional methods is small sample size. AMS needs 1milligram carbon or less for an analysis whereas conventional methods require at least a few grams of carbon. PRL-AMS presently tuned for radiocarbon, is successfully being used for dating variety of small size carbon samples. Basic features of the machine, efforts towards target preparations and some results on sub-milligram level carbon samples will be presented.

Quantitative elemental analysis of Rock samples by using the Laser Induced Breakdown Spectroscopy

Date: 2018-10-29
Speaker: Dr. Nageswara Rao Epuru
Venue: GF Lecture Hall

Abstract

The quantitative elemental estimation in rock samples is studied using Laser induced breakdown spectroscopy and in house developed the ratio-based CF-LIBS algorithm and synthetic spectrum generation methods. Main aim of this study is to estimate the accurate elemental compositions. As LIBS elemental analysis is based on some assumption such as Local thermodynamic equilibrium (LTE) conditions, optically thin, etc. the estimation by usual LIBS analysis does not give accurate elemental compositions. We have developed the ratio-based CF-LIBS algorithm as well as synthetic spectrum generation method. In synthetic spectrum method, the self-absorption effect is incorporated and results based on this is matching with the reference value obtained from the X-ray fluorescence (XRF) spectroscopy. In this seminar, I will discuss about the recent LIBS experiment on Rock samples and results. We have recently developed the Double pulse-LIBS setup in PRL and perform experiments for signal enhancement. The results on double pulse will be also discussed.

A Summary of Dust Detectors flown in past missions

Date: 2018-10-26
Speaker: Mr Srirag Nambiar
Venue: Room no 113, Thaltej Campus

Abstract

Mineralogy and Chronology of Domical Craters on the Moon

Date: 2018-10-12
Speaker: Nandita Kumari

Abstract

Impact cratering on Moon and Mars

Date: 2018-10-05
Speaker: Dr S Vijayan
Venue: Room no 113, Thaltej Campus

Abstract

Solar Radio Astronomy "CALLISTO instrument and the e-Callisto network"

Date: 2018-10-04
Speaker: Mr. Christian Andreas Monstein
Venue: USO Seminar Hall

Abstract

Evolution of 67P/Churyumov–Gerasimenko cometary coma as observed by Rosetta

Date: 2018-09-28
Speaker: Dr. Susarla Raghuram
Venue: Room no 113, Thaltej Campus

Abstract

Why and How Do You Experimentally Locate Local Minima? Some Case Studies using Matrix Isolation Infrared Spectroscopy

Date: 2018-09-20
Speaker: Prof. K Viswanathan
Venue: Room No. 006, PRL Thaltej

Abstract

Oftentimes, in the study of molecular conformations and weak non-covalent complexes, multiple minima are encountered. Molecules may exhibit more than one conformation of nearly equal energies. Likewise, non-covalent complexes, such as hydrogen bonded complexes may manifest more than one isomeric form of the complex, with comparable interaction energies. It is a non-trivial problem to study such multiple minima systems. Moreover, the multiple-minima may have a profound influence in the chemistry of such systems and hence warrants a detailed study. In the talk, we will discuss the importance of studying such systems and the experimental methodology that is best suited for such studies, with special reference to weak intermolecular interactions and conformations.

Evolution and characteristics of fine organic aerosol in the urban atmosphere through highly time resolved measurements

Date: 2018-09-18
Speaker: Dr. Atinderpal Singh
Venue: Ground Floor Lecture Hall

Abstract

Sub-micron particles are an integral part of Earth's atmosphere with significant impacts (direct and indirect) on air quality and climate. An unprecedented increase in sub-micron particles concentrations over urban regions is a serious threat to both air quality and climate. Organic aerosol (OA), although reported to be a dominant fraction of submicron aerosol, are least understood the component of fine aerosol due to their numerous sources, complex composition, tedious formation mechanism, and complicated atmospheric evolution. The OA can either be primary or of secondary origin. The primary OA (POA) are emitted directly in particulate form from various sources, whereas, secondary OA (SOA) is produced from the oxidation of volatile organic compounds (VOCs) coming from different sources. Furthermore, the composition and properties of both POA and SOA may change dynamically throughout the aerosol lifetime, because of intertwined processes including emission, oxidation, fragmentation, and gas-to-particle partitioning. Until recent years, most of the studies have reported the properties of OA using filters based measurements (offline) which has limitations in capturing OA evolution in the atmosphere due to a low time resolution of measurements. Toward this, the present study investigates the evolution of OA in real-time using high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) during the post-monsoon season over Ahmedabad.

Propagation characteristics of Coronal Mass Ejections

Date: 2018-09-18
Speaker: Mr. M. Syed Ibrahim
Venue: USO Seminar Hall

Abstract

Propagation characteristics of Coronal Mass Ejections (CMEs) are very important in the concept of space weather studies. In this presentation, I want to discuss three published works; these papers are published during my PhD. First, we tried to understand the CME propagation differences between the rising phase of solar cycles 23 and 24. Second, we analyzed the relationship between CME initial parameters and corresponding Geo-effectiveness (i.e. Dst, geomagnetic storm disturbances index). Using these relationships, we developed empirical equations for Dst forecasting with the function of CME initial parameters. Finally, we predicted ICME arrival times for four major Geo-effective CMEs during the rising phase of solar cycle 24 using Empirical CME Arrival model (ECA), and these estimated arrival times are compared with the observational results.

Quantum Ghost Imaging, Quantum Microscope and Entanglement Generation in Telecommunication regime

Date: 2018-09-17
Speaker: Dr. Sanjit Karmakar
Venue: Room No 113, PRL Thaltej

Abstract

In a broader sense, the exploitation of strange quantum mechanical phenomenon in practical applications to achieve more advantages than as usual is my interest. In this seminar, I will show that interest via both theoretical and experimental studies of quantum ghost imaging, the design of quantum microscope and theoretical studies of entanglement generation in telecommunication wavelengths. In the first part of this seminar, I will talk about quantum ghost imaging and its practical implication of a design of a quantum microscope with very high resolving power and non-invasive features. In quantum communication networks, the rules of quantum mechanics are used in practical communication networks. Quantum networks are capable of fulfilling the needs of secure networks: by using the technique of propagation of entanglement via an optical fiber link or free space, data are transferred as quantum states in these networks. For the future quantum network, it demands a highly efficient generator of entanglement states. In the final part of this seminar, I will present theoretical studies on efficient generation of entangled photon pair in the wavelength of telecommunication regime. In addition, I will talk about optical imaging through scattering media in brief.

Shockwaves in materials research

Date: 2018-09-17
Speaker: Dr. V Jayaram
Venue: Room No. 113, PRL Thaltej

Abstract

A review of shock tubes is made based on the various modifications starting from simple shock tube to high enthalpy shock tube such as free piston driven shock tube (FPST) to produce shock waves of short duration for materials research. Shock tubes are required in various fields such as material science, astro-chemistry, astro-physics, chemical kinetics, biomedical and aerospace applications. To produce high enthalpy test gases we designed and developed material shock tubes (MST1, MST2) and free piston driven shock tube (MST3). These shock tubes are used to produce reflected shock pressure and temperature of about 10-100 bar and 1500-25000 K for 1-2 ms duration. These facilities are used to studied interaction of different types of materials with shock heated test gases in the form of pellets and fine powders. These thermodynamic conditions can be controlled by changing test gas pressure and diaphragm thickness. Application of these shock tube facilities are presented briefly for material research.

The Largest Particle Accelerators of the Universe

Date: 2018-09-13
Speaker: Dr. Kamlesh Rajpurohit (TLS Observatory, Germany)

Abstract

Galaxy clusters are the most massive, gravitationally bound systems in the Universe and are unique laboratories to probe the physics of particle acceleration and magnetic field properties. Galaxy clusters are formed by accretion of gas and mergers with other clusters and galaxy groups. During cluster formation processes, some of the energy released is channeled into merger driven shocks and turbulences, leading eventually to the acceleration of particles to relativistic energies. However, the underlying particle acceleration mechanism is still being debated. In this talk, I will discuss how merging galaxy clusters can act as giant cosmological particle accelerators and about the magnetization of the intra-cluster medium.

Dynamical and chemical study of exoplanets and their host stars

Date: 2018-09-07
Speaker: Dr Shashanka Gurumath
Venue: Room no 113, Thaltej Campus

Abstract

TBA

Date: 2018-09-04
Speaker: Rukmani
Venue: Room No. 469

Abstract

TBA

Continuous variables quantum communications

Date: 2018-09-04
Speaker: Dr. Rupesh Kumar
Venue: Room No. 113, PRL Thaltej

Abstract

Circular differential scattering of achiral structures

Date: 2018-08-31
Speaker: Dr. Apurv Chaitanya N
Venue: Room No. 113, PRL Thaltej

Abstract

The differential optical response of a system for left and right circular polarized illumination has been widely used for the structural characterization of stereoisomers. Circular differential scattering is one of such techniques, which has become synonymous to "chiral geometry" of the system under consideration. In this talk we will discuss our recent findings claiming that even achiral structures can give raise to large differential optical response between right and left circular polarized excitation. We consider, plasmonic structure with mirror symmetry and show that the angular profile and intensity of the electric field in the farfield depends on the handedness of the circular polarized light with which it is illuminated. We investigate the individual contribution of the multipole moments to understand the source of the differential response of such achiral systems.

A photochemical model for Nitric Oxide in the upper atmosphere of Mars

Date: 2018-08-31
Speaker: Dr. Maneesha Dharwan
Venue: Room no 113, Thaltej Campus

Abstract

Some comments on Thapa-Pandey's discovery of room temperature superconductivity at IISc Bangalore

Date: 2018-08-30
Speaker: Dr. Navinder Singh, (THEPH, PRL)
Venue: Room No. 469

Abstract

Silver and gold are not good superconductors, they superconduct at micro Kelvin temperatures. At IISc Bangalore, Thapa and Pandey discovered that their amalgam consisting nanoparticles can superconduct at room temperature! If true and verified independently,this will be greatest discovery in the field of superconductivity. However, the discovery is veiled by an unexpected correlations in data. We present some comments on these developments.

C:N:P Ratio: A Driver of Ocean Biogeochemistry

Date: 2018-08-24
Speaker: Ms. Deepika Sahoo
Venue: Nano Sims Hall

Abstract

Until recently, carbon, nitrogen, phosphorous have been known to remain in a specific proportion (C:N:P = 106:16:1) in the ocean. This ratio is known as the Redfield ratio. Recent studies have reported that the C:N:P ratio in the dissolved inorganic nutrients and phytoplankton communities deviate from the canonical Redfield ratio. Growth rate and nutrient limitation hypotheses have been proposed to understand this variation in the world ocean. However, no stoichiometric studies have been undertaken in the northern Indian ocean, despite that this region is believed to provide a natural in situ laboratory to understand biogeochemical processes. In this talk, I will discuss the basic understanding of variation in stoichiometry in general, and the role of environmental factors affecting the variation in the Bay of Bengal using a conceptual model in particular.

The Orientale Basin on the Moon: Significance, Present Day Understanding & Potential for Future Exploration

Date: 2018-08-24
Speaker: Dr Neeraj Shrivastava
Venue: Room no 113, Thaltej Campus

Abstract

Paleoenvironmental study using Himalayan lake sediments.

Date: 2018-08-21
Speaker: Mr. Abdur Rehman
Venue: Ground Floor Lecture Hall

Abstract

environmental conditions at the regional scale and its linkages with past global climatic events. Stable isotopic compositions of different constituents of lake sediments, like organic matter and diatom, can be used as a powerful proxy to decipher palaeoenvironmental and biological conditions. During this talk, preliminary results obtained from high altitude Himalayan Lake sediments along with methodological endeavour towards measurements of oxygen isotopic composition in silicates will be discussed.

Approximate methods to model cosmological non-linear large scale structure

Date: 2018-08-20
Speaker: Dr. Sharvari Nadkarni-Ghosh (IIT Kanpur)
Venue: Room No. 469

Abstract

cosmological observations have shown that on large scales, matter is distributed into high density regions such as galaxies, clusters etc. and low density voids. Understanding how this large scale structure (LSS) arose from tiny quantum fluctuations set during inflation, is one of the important aims of cosmology today. The reason for this is because the evolution history depends sensitively upon the cosmological model and observations of LSS can help constrain the modelâ€™s parameters. Numerical simulations are widely employed to track the evolution into the non-linear regime; however they are slow. Given the wide range of cosmological models, this proves to be prohibitive and alternate analytic methods are necessary. Although approximate, they are not only faster but also provide valuable insight into the results of simulations. In this talk, I will describe two such approximate methods to model the non-linear evolution of large scale structure: Lagrangian perturbation theory (LPT) and ellipsoidal collapse. I will discuss the domain of validity of these methods and illustrate some applications.

Dark matter direct detection

Date: 2018-08-20
Speaker: Dr. Gaurav Tomar, Sogang Univ. Korea
Venue: Room No. 469

Abstract

Guided by non-relativistic EFT, we classify the most general interactions between scalar or fermionic WIMP and nuclei. Recently, we studied exclusion plots for different types of interactions which in WIMPs direct detection are the measure of the relative sensitivity of different experiments. We analyzed exclusion plots for newly arising non-standard interactions for existing experiments including the effects of isospin violation. We also discussed the spectral shape in WIMPs effective models and present the exclusion plots for current as well as future experiments. In this talk, we will talk about it in more details including the lastest result from DAMA phase-2 experiment.

Measurements of volatile organic compounds (VOCs) in marine boundary layer of Arabian Sea

Date: 2018-08-20
Speaker: Nidhi Tripathi
Venue: Ground Floor Lecture Hall

Abstract

Ozone in the troposphere is produced from the photochemical reactions of VOCs and other trace gases. Globally, VOCs are emitted from both anthropogenic and natural (oceanic and terrestrial) sources. The northern Indian Ocean particularly the Arabian Sea is one of the most productive regions where studies of oceanic VOCs are scarce. Dissolved organic carbon (DOC) in the seawater is an important source of many VOC compounds. My presentation is based on the measurements of important VOCs including alkenes and isoprene in the marine boundary layer of Arabian Sea during a cruise campaign in the pre-monsoon season. The objective is to determine the relation between the mixing ratios of VOCs in marine boundary layer with oceanic productivity and role of several environmental parameters. The preliminary analysis indicates significantly higher levels of VOCs compared to those measured over the Bay of Bengal. I will highlight the implications of elevated VOCs to the levels of ozone observed during the INDOEX campaign.

Constraining TeV scale Seesaw Models from electroweak vacuum stability/metastability.

Date: 2018-08-20
Speaker: Mr. Vishnudath, Physical Research Laboratory
Venue: Room No. 469

Abstract

The discovery of the Higgs boson with a mass of 125 GeV was a mileston in particle physics and it indicates that the Standard Model (SM) electroweak vacuum is metastable. But this is under the assumption that SM is the true theory up to the Planck scale. One of the major issues that SM does not have an answer to is the non-zero masses of the neutrinos as indicated by various neutrino oscillation experiments. Among the various proposals for neutrino mass generation, seesaw mechanism is the most famous one. In this talk, I will discuss how the new physics parameters could be constrained from the stability/metastability arguments in the context of natural type-3 seesaw model. We also consider the constraints coming from charged lepton flavor violating decays. Finally, I will also discuss a class of gauged U(1) extensions with inverse seesaw mechanism.

Probing Inert Higgs model with Jet-substructure

Date: 2018-08-20
Speaker: Ms. Akanksha Bhardwaj (PRL)
Venue: Room No. 469

Abstract

The Inert Higgs doublet model (IDM) is a theoretically well-motivated model among the Minimal Consistent Dark Matter (MCDM) models and provides many interesting signatures at the LHC. For hierarchical IDM scalar spectrum, the usual searches at the LHC are not efficient enough. In this ongoing work, we propose a new signature (2 Fat-jet + MET) to search for this interesting parameter space of this model. We choose the benchmark points by performing the parameter scan which satisfies all the theoretical and experimental constraints. We perform our analysis for light DM scenarios with the mass of 50-70 GeV, where we probe both the charged and the CP-odd Higgs in 300-700 GeV mass range. We exploit the characteristics of the jet substructure techniques which can lead to the discovery of the 2 fatjet + MET signal with the integrated luminosity of 3000 $fb^{-1}$ at the 13 TeV LHC.

Photon correlation properties of twisted single photons

Date: 2018-08-17
Speaker: Mr. Nijil Lal C K
Venue: Room No; 113, PRL Thaltej

Abstract

The demand for secure communication and high precision measurements have led to the emergence of single photon sources (SPS). Heralded single photon sources are considered as one of the most preferred SPS candidates. Incorporating the orbital angular momentum (OAM) as a degree of freedom, these single photon sources become more useful in many quantum information applications. The quantum nature of these sources is measured and characterized in terms of second order correlation function. During the talk, I will discuss the non-classical behaviour of single photons carrying orbital angular momentum. I will also discuss the analogous nature of photon OAM and number states in terms of second order correlation function.

NICSPol, A Near Infrared polarimeter for the 1.2m telescope at Mount Abu Infrared Observatory

Date: 2018-08-16
Speaker: Ms. Aarthy E. (PRL, Ahmedabad)
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

NICSPol is a near infrared imaging polarimeter developed for the Near Infrared Camera and Spectrograph (NICS), one of the back end instruments of the 1.2 m Cassegrain telescope at the Mount Abu Infrared Observatory (MIRO), India. The polarimeter consists of a rotating wire grid polarizer which is mounted between the telescope optics and NICS. NICSPol is a general purpose instrument which could be used to study various astrophysical sources like star forming regions, AGNs, Pulsars, XRBs, GRBs, Supernovae et cetera. The observations are carried out for sources by rotating the polarimeter at multiple angles to determine the Stokes parameters, which are then converted into the polarization fraction and polarization angle. In this talk I would brief about the instrument, data acquiring and analysis procedure. The performance of NICSPol is verified with polarimetric standards along with which a preliminary science result will also be discussed.

Understanding elementary processes in surface chemistry using state resolved molecular beam surface scattering experiments

Date: 2018-08-16
Speaker: Dr. Pranav R. Shirhatti
Venue: Room No. 113, PRL Thaltej

Abstract

Chemical reactions occurring on metal surfaces is a subject of wide interest, primarily because of its direct connections to heterogeneous catalyst technology. These processes are often complex and are composed of several elementary steps such as adsorption, diffusion, bond breaking/making and desorption. Moreover, each of these steps are accompanied by energy exchange with the underlying catalyst surface (often a metal) via different pathways and spanning different time scales. Understanding the energetics and dynamics of these elementary steps can have profound implications on our understanding of surface chemistry. In this talk, I will give an overview of some recent efforts in this direction especially focusing on studies involving quantum state resolved molecular beam surface scattering– experiments. Here, the incident molecules (on the target surface) are prepared in a precise quantum state distribution using a combination of molecular beam/laser pumping methods and the scattered molecules are detected using laser spectroscopy based techniques. In particular, I will discuss the case of unusually slow vibrational relaxation rate of CO on Au(111) surface,as suggested by the state resolved scattering experiments and its possible implications for reaction mechanisms in surface chemistry.

Gutzwiller mean field theory and exact diagonalization method for Bose-Hubbard model.

Date: 2018-08-16
Speaker: Mr. Soumik Bandhopadhyay
Venue: Room No. 469

Abstract

Bose-Hubbard model stands as the prototypical model to capture the physics of ultracold bosons in optical lattices. During this talk, I will describe three different methodologies, that is, single-site Gutzwiller mean field (SGMF), cluster Gutzwiller mean field (CGMF), and exact diagonalization (ED), which we have used to solve the model Hamiltonian in our studies. In order to emphasize the merits and drawbacks of each method, we will discuss on distinct quantum phases and their characteristics, exhibited by neutral and dipolar bosons in perfect or disordered optical lattices.

Oxidative potential of ambient aerosol over the Arabia Sea

Date: 2018-08-14
Speaker: Mr. Anil Patel
Venue: Ground Floor Lecture Hall

Abstract

In addition to in-situ production of reactive oxygen species (ROS) as a part of their metabolism during photosynthesis and respiration by phytoplankton in the marine system, atmospheric deposition of aerosol may also enhance ROS concentration in surface water. When the level of ROS exceeds the defense mechanisms, oxidative stress is generated which can pose a threat to cells by causing damage to bio-molecules such as DNA, lipids and nucleic acids. ROS have been hypothesized to reduce marine ammonia oxidation (nitrification) which may affect ocean biogeochemical cycle. To identify aerosol species responsible for ROS generation in the atmosphere and their major sources over the marine atmospheric boundary layer, aerosol samples were collected onboard SS-359 cruise over the Arabian Sea during April 2017 as a case study. Preliminary results of this study will be discussed.

Investigations of neutral wave dynamics using radio measurements

Date: 2018-08-13
Speaker: Mr. Subir Mandal
Venue: Ground Floor Lecture Hall

Abstract

Gravity waves (GWs) play an important role in the energy budget of the upper atmosphere. As they propagate though the atmosphere they modulate the atmospheric parameters like temperature, pressure, density of atmospheric species. Conventionally, GWs in upper atmosphere are measured using optical airglow emissions which are centered at some particular altitudes and hence carry information corresponding to those altitudes.The information on vertical propagation features of GWs in thermosphere are limited due to the fact that optical airglow emissions are integrated over a range of altitudes. We present results obtained using Digisonde measurement wherein analysis of height variation of iso-electron densities corresponding to different transmission frequencies are carried out. As vertical propagation of waves perturbs the electron density at different altitudes, we obtain GW scale sizes in the vertical direction in addition to other parameters. As Digisonde measurements are not limited to sky conditions, this approach enables investigations of GW behavior in the upper atmosphere in all seasons and all times. Using Hines dispersion relation we derive horizontal scale sizes. In this background, I will present the results obtained and describe the details of the method of obtaining the propagation characteristics of GWs. The results from the radio measurements compare well with those obtained from the established optical measurements, both in day and nighttime.

Spectral and Timing studies of Be X-ray binary pulsar 2S 1417-624

Date: 2018-08-13
Speaker: Shivangi Gupta
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Be/X-ray binaries are among the brightest transient X-ray sources in our Galaxy. The compact object in these systems (which is a mostly a neutron star), revolves in a wide eccentric orbit around massive Be spectral type optical companion. These sources show periodic or Type-I X-ray outbursts, usually associated with periastron passage of binary. It is believed that neutron star accretes matter from a circumstellar disk around the Be star and powers such a strong outbursts. Another kind of X-ray enhancements, Type-II outbursts are also displayed by these systems, which are quite rare and independent of the orbital phase of the binary system. These rare events provide a unique opportunity to probe the emission geometry of these binary system. In this talk I will present results obtained from the spectral and timing studies of such a source, 2S 1417-624 during a Type-II outburst in 2009, using RXTE observations.

Venus Cloud Dynamics and Meteorology Experiment for Venus Balloon

Date: 2018-08-10
Speaker: Chandan Kumar
Venue: Room no 113, Thaltej Campus

Abstract

An Infrared study of dark cloud : LDN1340

Date: 2018-08-09
Speaker: Ms. Archita Rai (PRL, Ahmedabad)

Abstract

Lynds dark nebulae (LDN) are dark patches seen against the background stars of the Milky Way. They are thought to be the birth places for stars. A catalog of these dark nebulae was made in 1960 by Beverly Turner Lynds, who visually inspected large areas of the Milky Way on the Palomar-Schmidt Survey Plates (POSS). As these regions have large opacity (range ~ 1 to 6) & extinction caused by high density and interstellar dust, the stars embedded in the dark clouds may not be visible in the optical band. To study them, infrared wavelength are expected to provide us with more penetration depth to study the core of the clouds. Hence more stars can be detected and the phenomena like polarisation and extinction which depend upon the distribution of the interstellar dust and the interstellar magnetic field can be studied in detail. In my talk, I will give a brief introduction to one of the Lynds clouds (LDN1340) and discuss its behaviour and properties. I will be discussing the observational aspects of using NICSPOL at the Mt. Abu Infrared Observatory along with other archival photometric data for this study.

Sea water δ18O and δD dynamics over the Northern Indian Ocean

Date: 2018-08-07
Speaker: Mr. Kiran Kumar P.
Venue: Ground Floor Lecture Hall

Abstract

Sea water oxygen isotopic composition (δ18O) is a widely used proxy to study modern and past dynamics of the ocean. δ18O-Salinity relation in the surface ocean is a useful tracer to study imprints of physical processes, such as runoff, sea ice melting, large-scale ocean mixing and also paleo-salinity. Effect of precipitation (P), runoff (R) and evaporation (E) in the surface ocean as a ‘P+R-E’ budget on δ18O, δD and S is relatively well understood, however in the subsurface waters it still remains elusive. In this seminar I will discuss a new data set of δ18O, δD and Salinity for the surface and subsurface sea water samples collected from the northern Indian Ocean during pre and post-monsoon months in 2016 and 2017 and highlight various controlling processes

Evolution of Coronal Cavity from Quiescent to Eruptive Phase in Association with Coronal Mass Ejection

Date: 2018-08-07
Speaker: Mr. Ranadeep Sarkar
Venue: USO Seminar Hall

Abstract

The initiation mechanism of coronal mass ejections (CMEs) remains among the most elusive topics in solar physics. The initiation and triggering of CMEs can be studied by observing the coronal cavities in the lower coronal regions. These cavities appear as dark features and are believed to be the density depleted cross-sections of the magnetic flux ropes, where the magnetic field strength attains a much higher value compared to the background corona. Cavities may last for days or even weeks and evolve as the dark core part of the CME during the eruptive phase. In order to understand the pre-eruptive stability conditions for quiescent cavities and the triggering mechanisms for those structures to erupt, it is important to study the morphological evolution of the coronal cavities. In this work, we study the evolution of a cavity in lower corona using the observations from STEREO SECCHI/EUVI and PROBA2/SWAP EUV imager. In the quiescent phase, the cavity centroid height slowly rises from 1.10 to 1.23 RS during its passage on the visible solar disc from May 30 to June 13, 2010 and its initial circular shaped morphology gradually expanded and evolved into elliptical shape prior to the eruption from the western solar limb. The extended field-of-view of SWAP fills the observational gap between 1 to 2 RS. It enables us to capture the complete evolution of the erupting cavity starting from its EUV counterpart in the lower corona up to the white light cavity morphology seen in LASCO C2/C3 field-of-view. During the eruptive phase, we have observed a significant non-radial motion of the cavity at a very low coronal height of 1.3 RS. Furthermore, the geometrical fitting to the cavity morphology in different time-steps during its eruptive phase reveals that it exhibits non self similar expansion in the lower corona. We also discuss the role of the background magnetic field and the possible instabilities which may lead to the non-radial motion and initiation of the cavity eruption respectively.

Sterile Neutrino Search

Date: 2018-08-06
Speaker: Mr. Kaustav Chakraborty (PRL)
Venue: Room No. 469

Abstract

The recent MiniBooNE data is consistent in energy and magnitude with the excess of events reported by the Liquid Scintillator Neutrino Detector (LSND). This excess corresponds to a ∆m2 ∼ 0.04eV which hints towards the presence of a light sterile neutrino. I will talk on the evidence of sterile neutrino and the future prospects of sterile neutrino search. I will also talk on ‘partial µ-τ ’ reflection symmetry in the context of sterile neutrino. The predictions of this symmetry is compared with the allowed area in the sin2θ23 − δCP plane as obtained from the global analysis of neutrino oscillation data.

Noble gases and HED meteorites

Date: 2018-08-03
Speaker: Ramakant R Mahajan
Venue: Room no 113, Thaltej Campus

Abstract

A ROBUST SIGNATURE OF ELECTRON HYDRODYNAMICS IN 2D MATERIALS

Date: 2018-08-02
Speaker: Prof. Deshdeep Sahdev, Quazar Tech, (New Delhi)
Venue: Room No. 469

Abstract

Electron transport can transition from Ohmic to hydrodynamic when electron-electron scattering dominates, as shown in several recent experiments in systems such as Graphene. We show that microwave-frequency AC sources can excite hydrodynamic behavior involving vigorous vortex generation and reconnection, far more easily than the DC sources used so far. We identify the change of sign in a nonlocal current-voltage phase as a robust probe of the transition to the electronic hydrodynamic regime.

Analysis of atmospheric effects on satellite-based quantum communication: A comparative study

Date: 2018-08-02
Speaker: Mr. Vishal Sharma
Venue: Room 113, PRL Thaltej

Abstract

Quantum Key Distribution (QKD) is a key exchange protocol which is implemented over free space optical links or optical fiber cable. When direct communication is not possible, QKD is performed over fiber cables, but the imperfections in detectors used at the receiver side and also the material properties of fiber cables limit the long-distance communication. Free-space based QKD is free from such limitations and can pave the way for satellite-based quantum com-munication to set up a global network for sharing secret messages. To implement free space optical (FSO) links, it is essential to study the effect of atmospheric turbulence. Here, an analysis is made for satellite-based quantum communication using QKD protocols. The results obtained indicate that SARG04 protocol is an effective approach for satellite-based quantum communication.

Lakshadweep corals and their paleoclimate proxy records

Date: 2018-07-31
Speaker: Mr.Harsh Raj
Venue: Ground Floor Lecture Hall

Abstract

Corals are important natural archives of paleoclimate proxy records. They provide high resolution proxy records of past climate and ocean. These high-resolution proxy records can be used to study past changes in monsoon and sea surface conditions. In Indian context, earlier studies were carried out on Lakshadweep corals establishing them as faithful recorder of sea surface temperature changes. In recent years Lakshadweep corals show reduced growth rate, which could be related to warming of surface waters in the region. Lakshadweep also receives good amount of rainfall during summer monsoon season, however in previous studies no correlation has been observed between monsoon precipitation in coral proxy records. In this talk, I will discuss coral proxy data and possibility of coral recording monsoon signatures.

Inflationary Cosmology: Theory and Observations

Date: 2018-07-30
Speaker: Ms. Richa Arya (PRL)
Venue: Room No. 469

Abstract

Cosmological Inflation is a phase of accelerated expansion for a very brief duration in the early Universe. It provides a solution to many shortcomings of the Standard Big Bang Model of cosmology. As a bonus, it also generates the density fluctuations that explain the anisotropies in the Cosmic Microwave Background (CMB) radiation and seeds the growth of Large-Scale Structures (LSS) at the late time. In this talk, I will review the inflationary paradigm and discuss various inflationary models and their status from the current CMB observations. I will also discuss some results of our study on the Warm Inflationary models.

Vega Balloon System and Meteorology Suite

Date: 2018-07-27
Speaker: Chandan Kumar
Venue: Room no 113, Thaltej Campus

Abstract

Non-holomorphic supersymmetry and scalar sequestering

Date: 2018-07-27
Speaker: Sabyasachi Chakraborty, TIFR Mumbai
Venue: Room No. 469

Abstract

Scalar sequestering ensure vanishing masses for supersymmetric scalars at high scales. This interesting feature is a result of strong dynamics in the hidden sector and highly motivated from the perspective of electroweak fine tuning. In such a scenario, gaugino mediated loop suppressed contributions generate scalar masses at the TeV scale. Naturally, right handed sleptons turn out to be the lightest SUSY particles rendering a cosmologically unfavorable spectrum. In this work, we solve this issue by considering non-holomorphic soft susy breaking operators. We found out that the presence of such operators leaves a non-trivial imprint on the renormalization group evolutions of the scalar masses, resulting in a viable spectrum. Extension of this result can also be applied to other frameworks such as no-scale SUGRA, gaugino mediation, anomaly mediation etc.

TBA

Date: 2018-07-26
Speaker: Mr. Ashish Narang (PRL)
Venue: Room No. 469

Abstract

TBA

Aqueous Alteration Characteristics of Mukundpura Meteorite: A preliminary study using EPMA

Date: 2018-07-20
Speaker: Dipak Kumar Panda
Venue: Room no 113, Thaltej Campus

Abstract

Constraint on viscosity of dark matter from the 21 cm signal

Date: 2018-07-19
Speaker: Mr. Arvind Kumar Mishra (PRL)
Venue: Room No. 469

Abstract

Recently the Experiment to Detect the Global Epoch of Re-ionization Signature (EDGES) has reported an absorption signal of 21cm emitted from the hyperfine splitting of the neutral hydrogen in the cosmic dawn era. The amplitude of this absorption dip indicates that the baryons were much cooler than as expected from the standard cosmology. This can be explained by considering the interaction between dark matter and baryonic matter. In the standard cosmology, one assumes the dark matter to be an ideal fluid. In our work, we consider dark matter as a viscous fluid and try to constraint its viscosity from the 21 cm signal. In this talk, I will discuss about the 21 cm signal and show some preliminary results of our work.

Cold gas in high redshift galaxies

Date: 2018-07-16
Speaker: Dr. J.N.H.S. Aditya
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Cold HI gas at high redshifts can be probed using HI 21 cm absorption against background radio-loud Active Galactic Nuclie (AGN). The distribution and kinematics of this gas, present in the vicinities of the AGN, can be studied using this technique. A large number of surveys in last 50 years have reported nearly 140 detections of such `associated' HI 21 cm absorbers. However, most of these studies are limited only to low redshifts (z < 1). Using GMRT we have carried out a search for associated HI 21 cm absorption in a large and uniformly selected sample of 76 flat-spectrum radio AGN that inclues 50 sources at z > 1. For the first time, we find a statistically significant evidence (~3-sigma) that the strength of associated HI 21 cm absorption in the high-z sub-sample is lower than that of the low-z sub-sample. Also, we detect four new HI 21 cm absorbers at z > 1, increasing the total number of known absorbers at z > 1 to eight. The possible causes for the low absorption strength at higher redshifts can be : (1) redshift evolution in the AGN environments, (2) high UV and/or radio luminosity of high-z AGN, and (3) low gas covering factor in high-z AGN. These plausibilities are further investigated in Giga-Hertz Peaked Spectrum (GPS), High-Frequency Peaker (HFP) and other AGN with compact radio-jets. I shall present the details of our surveys and the studies of individual cases of newly-detected HI 21 cm absorbing systems.

Study of multi-wavelength emissions from solar flares

Date: 2018-07-16
Speaker: Mr. Prabir Kumar Mitra
Venue: USO Seminar Hall

Abstract

Caused by magnetic reconnection and a sequence of subsequent physical processes, huge amount of energy is radiated over the entire electro-magnetic spectrum during solar flares. Multi wavelength observation and analysis are extremely important to understand the different physical processes during flares, which occur at different layers of the Sun (i.e., Photosphere, Chromosphere, Corona). During September 4-10, 2017, an active region (NOAA 12673) became very active and produced a series of many large flares (27 M-class and 4 X-class) including the largest flare in the solar cycle 24 which occurred on September 6, 2017. We have analyzed the evolution of the active region during the aforementioned time interval and conducted a multi-wavelength study of the homologous X-class flares on September 6, 2017.

Quarkonia: A probe of QGP

Date: 2018-07-12
Speaker: Mr. Balbeer Singh (PRL)
Venue: Room No. 469

Abstract

Quark-gluon plasma (QGP) is the deconfined state of strongly interacting matter. Experimentally, this phase is accessible by colliding two heavy nuclei at sufficiently high energy. In view of this, RHIC@Brookhaven and LHC@CERN have created a unique opportunity to study the properties of QGP. In addition, a very strong magnetic field is also created at the initial stages of the collision which however decreases very rapidly and has a significant effect on the medium. The global properties of this deconfined matter are characterized by measurement of particles in low and high transverse momentum regime, jets, elliptic flow etc. In this regard, suppression of Quarkonium is considered as one of the important probes for QGP. In this talk, I will talk about the effect of magnetic field on heavy quark complex potential. Furthermore, I will also talk about the matrix model of semi QGP.

Magnetic reconnection in solar corona

Date: 2018-07-12
Speaker: Ms. Sushree Sangeeta Nayak
Venue: USO Seminar Hall

Abstract

Rearrangement in the magnetic field configuration due to the fundamental process called magnetic reconnection accompany eruptive phenomena like flares and coronal mass ejection in the solar atmosphere. There are different potential sites of magnetic reconnection in both 2D (X-type, Y-type, and O-type)and 3D(Spine -fan configuration and quasi-separatrix layers). These configurations are ubiquitous in the solar corona and are also proved to be responsible for dynamics observed there. In this talk, I will discuss the aforementioned structures which are constructed numerically from the photospheric field. For the purpose of the understanding of the involved dynamics, I will also present their magnetohydrodynamics evolution.

$\sigma_8$ tension and neutrino mass in dark energy models

Date: 2018-07-09
Speaker: Mr. Priyank Parashari (Physical Research Laboratory, Ahmedabad)
Venue: Room No. 469

Abstract

The current observations indicate that the present Universe is undergoing the accelerated expansion, which can be explained by the presence of dark energy (DE). The cosmological constant is the simplest candidate for dark energy but it has some problems. In this talk, I will discuss two DE models, (1) Hu-Sawicki (HS) Model of f(R) gravity and (2) Chavallier-Polarski-Linder (CPL) parameterization of dynamical dark energy (DDE), both of which explain the cosmic expansion. Also, in the standard model of cosmology it has been pointed out that there exists a tension in $\sigma_8-\Omega_m$ measurement between CMB and LSS observation. We compute $\sigma_8$ consistent with the parameters of HS and DDE models.I will discuss the status of $\sigma_8$ tension in the HS and DDE models. Since modified cosmology models change the matter power spectrum which also depends upon the neutrino mass, bound on neutrino mass gets modified. I will also discuss the bound on neutrino mass in the HS and DDE models.

Accretion on to LMXBs: A multi-wavelength approach

Date: 2018-07-06
Speaker: Mr. Sandeep Rout (PRL, Ahmedabad)
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Most Low mass X-ray binaries (LMXBs) show a transient behavior wherein they spend most of their life in quiescence and occasionally undergo outbursts due to instability in the accretion disk. These sources pose a unique opportunity to study the properties of the entire accretion disk especially of the relatively cool outer disk as the contribution of the companion star is negligible. One such soft X-ray transient GRS 1716-249 had been in an outburst during December 2016 and was observed in optical and infrared bands from Mt Abu Infrared Observatory. Towards the end of the outburst period, it was also observed by AstroSat as a ToO source. Combining the data obtained from Optical/IR and X-rays (3.0 - 100 keV) a multiwavelength analysis is attempted which promises to provide better constraints on black hole mass, disk outer radius etc. and help in expanding our understanding of various energetic processes occurring at the disk. In the seminar, I will discuss the general theory of accretion disks followed by the work carried on so far on the above object.

Methods of lunar refractory elements mapping: application to the Moscoviense basin - part 2

Date: 2018-07-06
Speaker: Dr. Megha Upendra Bhatt
Venue: Room no 113, Thaltej Campus

Abstract

Pinning the light pseudoscalar in Lepton Specific 2HDM

Date: 2018-07-03
Speaker: Mr. Siddharth Dwivedi, (Harish-Chandra Research Institute, Allahabad)
Venue: Room No. 469

Abstract

We investigate the detectability as well as reconstructibility of a light pseudoscalar particle $A$, of mass in the 50 -- 60 GeV range, which is still allowed in a Type-X (lepton-specific) two-Higgs doublet scenario. Such a pseudoscalar can be pair-produced in the decay $ h\to AA$ of the 125 GeV scalar $ h $. The light pseudoscalar in the aforementioned range, helpful in explaining the muon anomalous magnetic moment, has not only substantial branching ratio in the $\tau^+ \tau^-$ channel but also one of about $0.35\%$ in the $\mu^+\mu^-$ final state. We show how to faithfully reconstruct the $A$ mass using the $\mu^+\mu^-$ mode, and establish the existence of a pseudoscalar around 50 -- 60 GeV, using the process $pp \to h \to AA \to \mu^+\mu^- , \tau^+ \tau^-$. This is one of the most reliable ways of reconstructing the light $A$ mass, with a statistical significance that amounts to discovery, within the luminosity reach of Run-II at LHC.

Coronal magnetic field extrapolation techniques

Date: 2018-07-03
Speaker: Ms. Kamlesh Bora
Venue: USO Seminar Hall

Abstract

The most magnificent and dangerous indication of solar activity, flares and coronal mass ejections (CMEs), occur in the solar corona, and are believed to be powered by free magnetic energy stored in the coronal magnetic field. Modeling and measurement of the coronal magnetic field have been urgent targets of solar physics for many years. We have studied extrapolation techniques: potential or current-free, linear force-free, and non-force-free respectively. For this purpose we choose vector magnetogram of AR12673 on 06-09-2017 at 11:48UT from HMI/SDO. We have also developed codes for potential and linear force-free extrapolations. We compared the field line topology over and near the polarity inversion line(PIL) and noted that EUV brightenings in 131 and 304 angstrom channel along with vector magnetogram matches exactly with non-force-free extrapolation. We have found a 3-D null point using linear force-free technique over the PIL where the flare took place.

Photon probes at colliders

Date: 2018-06-29
Speaker: Ms. Disha Bhatia (TIFR Mumbai)
Venue: Room No. 469

Abstract

In this talk, I will be mainly concentrating on two new physics scenarios--- light and heavy, which could give rise to apparent diphoton signatures at LHC. I will be describing their phenomenological implications and detection methods in detail.

Methods of lunar refractory elements mapping: application to the Moscoviense basin

Date: 2018-06-29
Speaker: Dr. Megha Upendra Bhatt
Venue: Room no 113, Thaltej Campus

Abstract

TBA

Date: 2018-06-28
Speaker: Mr. Bhavesh Chauhan
Venue: Room No. 469

Abstract

TBA

Characteristics of Solar flares on Martian ionosphere

Date: 2018-06-22
Speaker: Siddhi Shah
Venue: Room no 113, Thaltej Campus

Abstract

Topic- Color Superconductivity for Magnetized three flavour quark matter

Date: 2018-06-21
Speaker: Mr. Aman Abhishek
Venue: Room No. 469

Abstract

At high enough density the quark matter becomes deconfined and the fermi surface is unstable to cooper pair formation. Such a phenomenon is known as Color superconductivity. There are various phases of color superconductivity which can be modified in the presence of external background magnetic field. Such a phase may be present in the interior of neutron stars. In the present work we study the color superconductivity in three flavor quark matter in the presence of magnetic field within the framework of Nambu-Jona Lasinio model. I will also discuss the effect of charge neutrality on color superconductivity.

Surface modifications due to soft landing on Moon

Date: 2018-06-15
Speaker: Sanjeev Kumar Mishra
Venue: Room no 113, Thaltej Campus

Abstract

Decoding cosmic fingerprints: constraining the generation and evolution of primordial fluctuations

Date: 2018-06-14
Speaker: Dhiraj kumar hazra
Venue: Room No. 469

Abstract

It is the origin and evolution of quantum fluctuations that eventually lead to the formation of the Large Scale Structure (LSS) in the Universe. The primordial perturbations emerge through the radiation and thereafter the matter dominated epochs and finally to today's dark energy dominated epoch, leaving their distinct fingerprints in the photons that we observe. Photons from the Cosmic Microwave Background (CMB), quasars, galaxies and clusters, supernovae, stars etc. can be analyzed to trace these fingerprints. In this talk, I will mainly discuss decoding three different fingerprints originating from three different epochs in the timeline of the Universe, namely, CMB from the last scattering surface, Lyman-alpha observations from reionization and post-reionization eras and the galaxies observed in the LSS. Since signals from different cosmological processes are convolved in our observations, effective joint analyses are required to converge towards the most probable model of the Universe. I will outline the standard model and few extensions beyond that agree remarkably with the present data. I will also discuss model independent reconstruction methods that can lead to possible scenarios of the Universe directly from the data. I will conclude with forecasts from the upcoming and proposed cosmological missions.

Oldest to infant rocks: Hadean mantle story

Date: 2018-06-12
Speaker: Dr. Ikshu Gautam
Venue: Ground Floor Lecture Hall

Abstract

The Hadean Eon, representing the first five hundred million years of Earthâ€™s history, was one of the most eventful periods when the planet got differentiated to various chemical layers based on density. One of these major events was the segregation of core and mantle from bulk Earth. Direct evidence for subsequent differentiation of the earliest differentiation of mantle is difficult to find, as the preserved Hadean rock record is scanty. However, information about these events can be obtained with the help of extinct radioactivity, in particular from 146Sm-142Nd systematics (Half-life of 103 Ma). Surprisingly, such evidence is not only restricted to the oldest rocks but also found in some infant rocks. In this talk I will discuss recent findings which provide a new perspective on the preservation of such evidence through geologic time. Some similar efforts by us in this direction will also be discussed.

Water-rock interaction on Mars: In-situ and microscopic observations

Date: 2018-06-08
Speaker: Dr. Amit Basu Sarbadhikari
Venue: Room no 113, Thaltej Campus

Abstract

Karst Geomorphology, Cave Development, and Hydrological Characterisation of Karst Aquifers in the Kashmir Valley, Western Himalaya, India.

Date: 2018-06-05
Speaker: Dr. Rouf Ahmad Shah
Venue: Ground Floor Lecture Hall

Abstract

Karst aquifers contribute substantially to freshwater and thermal water supplies in many region of the world. Kashmir Valley, one of the largest karst region on the Indian Subcontinent and the Himalaya, provides significant karst geomorphic imprint due to wide distribution of carbonate rocks. Karstified carbonate rocks has a high hydraulic conductivity ~1000m d-1, thereby, represents a major hydrogeological unit and a regionally important groundwater reservoir. Dissolution of carbonate rocks, (development of exokarstic and endokarstic features), abundant water resources in the form of large cold and warm springs, and subsequent development of floating gardens designed at spring outlets, has led to label the karst areas in the region as State Geoparks, which features the region a popular holiday destination, a backbone to regional economy. Past phreatic morphology and present relict nature suggest that the landscape evolution has changed the hydrologic conditions from phreatic to vadose, and thereby, modified the processes of speleogenesis and the characteristics of the caves. The uplift and erosion in Pilo-Plestocene is dynamic cause which governed the processes of karst development, likewise, climatic oscillations in the same period changed the solutional rates, and dominance of either chemical or mechanical. Although the spring ﬂow is dominantly controlled by the melting of snow and/or glaciers, rain events produce sharp spikes in spring hydrographs, primarily responsible for the undulating/seasonal trend in the δ2H and δ18O of the karst springs. Furthermore, the study provides new insights in understanding the dominant factors affecting the isotopic composition of the precipitation, snowpack, glacier melt, streams and springs. δ18O/ or δ2H of precipitation, snowpacks, glacier melt and karst springs show wide variation both in space and time, and are strongly inﬂuenced by the basin relief and meteorology. Similar temporal trends of isotopic signals in streams and karst springs reflect the rapid flow transfer due to karstification of the carbonate aquifers. Tracer breakthrough curves (TBC), retrieved for different springs suggest short travel time (2 to 7 d) and rapid conduit flow, which has practical consequences like, deterioration of water quality and variation in magnitude of groundwater flux in the region.

TBA

Date: 2018-06-04
Speaker: Mr. Arun Kumar Pandey
Venue: Room No. 469

Abstract

TBA

Determination of Martian Atmospheric Heating Rates

Date: 2018-06-01
Speaker: Mr. Masoom Jethwa
Venue: Room no 113, Thaltej Campus

Abstract

Monitoring of Himalayan and Polar Cryosphere using Earth observation data from orbiting satellites

Date: 2018-05-29
Speaker: Dr. Ishmohan Bahuguna
Venue: Ground Floor Lecture Hall

Abstract

Competing pathways in odd oxygen photochemistry of the Martian atmosphere

Date: 2018-05-18
Speaker: Mr Ashimananda Modak
Venue: Thaltej Campus

Abstract

Magnetohydrodynamic simulation of magnetic null-point reconnections in NOAA AR12192 initiated with an extrapolated non-force-free-field

Date: 2018-05-08
Speaker: Dr. Avijeet Prasad
Venue: USO Seminar Hall

Abstract

Magnetohydrodynamics of the solar corona is simulated numerically. The simulation is initialized with an extrapolated non-force-free magnetic field using the vector magnetogram of the active region (AR) NOAA 12192 obtained on the solar photosphere. Particularly, we focus on the magnetic reconnections occurring close to a magnetic null-point that resulted in appearance of circular chromospheric flare ribbons on October 24, 2014 around 21:21 UT, after peak of an X3.1 flare. The extrapolated field lines show the presence of the three-dimensional (3D) null near one of the polarity inversion lines, where the flare was observed. In the subsequent numerical simulation, we find magnetic reconnections occurring near the null point, where the magnetic field lines from the fan-plane of the 3D null form a X-type configuration with underlying arcade field lines. The footpoints of the dome-shaped field lines, inherent to the 3D null, show high gradients of the squashing factor. We find slipping reconnections at these quasi-separatrix layers, which are co-located with the post-flare circular brightening observed at the chromospheric heights. This demonstrates the viability of the initial non-force-free field along with the dynamics it initiates. Moreover, the initial field and its simulated evolution is found to be devoid of any flux rope, which is in congruence with the confined nature of the flare.

Effects of Solar X-ray flare and CME on the Martian Ionosphere

Date: 2018-05-04
Speaker: Prof. S A Haider
Venue: Room 113, Thaltej Campus

Abstract

Efficient generation of quantum twisted photons

Date: 2018-05-04
Speaker: Mr. Ali Anwar M A
Venue: Room No. 113, PRL Thaltej

Abstract

Light carrying orbital angular momentum (OAM), generally known as optical vortex, finds applications mainly in optical tweezers and optical communication. Conventional optical vortices have their limitations in applications involving transmission of OAM modes through optical fibers, as the size of the vortex strongly depends on its topological charge, therfore, coupling to fixed core fibers becomes difficult for higher order OAM modes. A new class of optical vortex beam, termed as 'perfect optical vortex' (POV) solves the size effects of a normal vortex beam. Conventioanally, POVs are formed as a Fourier transform of Bessel-Gaussian (BG) beams. In my talk, I'll explain about the generation of heralded single photons carrying OAM (quantum twisted photons) using spontaneous parametric down-conversion. Further, I'll show that the efficiency of generated twisted photons can be improved for higher OAM values with the use of BG beams or POVs as pump. The present studies may be useful in the efficient generation of higher dimensional OAM entangled states.

X-ray Superflares on Solar-type Stars

Date: 2018-05-03
Speaker: Dr. Subhajeet Karmakar

Abstract

Flares on the Sun and the stars are generally interpreted as a rapid and transient release of magnetic energy in coronal layers driven by reconnection processes, associated with electromagnetic radiation from radio waves to γ-rays. The typical total energy of a solar flare ranges from 10^29 to 10^32 erg, whereas Superflares are defined as the flares with the total energies of 10^33–10^38 erg. Although there are few hundreds of Superflares have been already discovered in optical waveband, the discoveries of X-ray superflares are still rare events (only nine have been discovered). The study of superflares on solar-type stars provides us important constraints of the upper end of the dynamical behavior of stellar corona as well as it helps us to probe the possibility of superflares on the Sun. In this seminar, I will talk about the analysis of three X-ray superflares. The first two superflares occurred on a fast-rotating (period of 1.56 day) main-sequence star CC Eri, and the third one occurred on an evolved 3.966-day period RS CVn type eclipsing binary system SZ Psc. In case of the superflares from CC Eri, it has been found that the flares decay faster in the hard X-ray band than in the soft X-ray band. Both flares are highly energetic with respective peak X-ray luminosities of ∼10^{32.2} and ∼ 10^{31.8} erg s^{−1} in 0.3-50 keV energy band. The time-resolved spectral analysis during the flares shows the variation in the coronal temperature, emission measure, and abundances. The observed peak temperatures in these two flares are found to be 174 and 128 MK. Using the hydrodynamic loop modeling, we derive loop lengths for both the flares as 1.2+/-0.1 x 10^{10} cm and 2.2+/-0.6x10^{10} cm, respectively. The Fe Kα emission at 6.4 keV is also detected in the X-ray spectra and we model the Kα emission feature as fluorescence from the hot flare source irradiating the photospheric iron. These superflares are the brightest, hottest, and shortest in duration observed thus far on CC Eri. On the other hand, the superflare on SZ Psc lasted very long duration for more than 100 ks, which is the longest duration X-ray flare ever observed as the best of our knowledge. Spectral analysis indicates a presence of one temperature corona, which represents the flare temperature. The temperature is one of the highest observed spectroscopically with a peak at 258 MK, which is ∼10 times more than the observed minimum value. The length of the flaring plasma was derived to be 7.3 x 10^{11} cm. The longer coronal loop and high level of magnetic activity at the coronal height for the RS CVn type binary star is probably due to the presence of extended convection zone of the sub-giant and the high orbital velocity.

Astronomy & Astrophysics Division Seminar

Date: 2018-05-01
Speaker: Mr. Kumar Venkataramani (PRL, Ahmedabad)

Abstract

Comets are cold, icy bodies in the Solar system that were formed in the early solar nebula. They are considered to be the signature bodies for investigating the formation of the Solar system. As a comet nucleus makes its journey towards the Sun, the ices start sublimating, giving rise to a mixture of gas and dust that forms the coma. Cometary molecular emissions are well known and have been studied since a long time. A typical optical spectrum of a comet with well developed coma shows molecular emissions dominated by carbon chain molecules like C2 and C3. NH2 and CN are two other species which show prominent emission lines in the optical spectrum. In general, these molecular emissions start appearing sequentially when the comet comes closer than 3 AU to the Sun. The most likely emission to appear first is that of CN molecule at around 3 AU, followed by the rest of the emissions. There are very few instances, when these pristine ice balls show a distinct behavior as compared to the regular oort cloud and jupiter family comets. Such a behaior is a consequence of its distinctive processing at the location of its formation in the early solar nebula. The spectroscopic observations of the comet C/2016 R2 have revealed its unusual behavior in the last few months. The results from the study of this distinct visitor to the inner solar system would be discussed in this talk.

The Martian Ionosphere -Theory and Observations

Date: 2018-04-27
Speaker: Prof. Varun Sheel
Venue: Room 113, Thaltej Campus

Abstract

Nitrogen dynamics in ecosystems with contrasting climate

Date: 2018-04-24
Speaker: Ms. Niharika Sharma
Venue: Ground Floor Lecture Hall

Abstract

Study of biogeochemical cycling of elements is very important in understanding the changes and responses of ecosystems towards the changing climate. Elemental circulation, its amount and availability within an ecosystem defines the health of ecosystem and species present in it. Nitrogen (N) is one such element which is required by all the species, as it serves as a growth limiting nutrient. Plants also require N for photosynthesis: a process to fix atmospheric CO2 into biomass, thus acts as carbon sink. N, if present in excess, can cause severe damage to ecosystems by emitting greenhouse gases (N2O) in the atmosphere, polluting water bodies (eutrophication) and result in biodiversity loss. In my talk, I will discuss about biogeochemical cycling of N in two different terrestrial ecosystems. These ecosystems differ from each other in terms of vegetation, land-use and climate. I will also compare the N dynamics within these ecosystems to address the differences and controls of N cycle.

Enigma of Be/X-ray binary pulsars near the critical luminosity

Date: 2018-04-24
Speaker: Mr. Prahlad Epili
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Be/X-ray binaries (BeXBs) form a major sub-group of High mass X-ray binaries. In these systems, a neutron star (also a pulsar) co-rotates with a normal O or B-type star, and accretes a copious amount of matter from an extended disk. Accretion of the matter into the enormous gravitational field of neutron star gives rise to X-ray outbursts. Most of the high energy emission originates from a tiny region on the surface of the pulsar, known as accretion column. For the present study, two BeXB pulsars were probed using RXTE, Suzaku and NuSTAR observations to understand the column emission, its geometry, and spectral characteristics as a function of mass accretion rate. We have also seen that the luminosity dependence of pulse profiles and spectral parameters could explain the existence of different accretion regimes (above and below a specific or critical luminosity) in these sources. It also helped us in estimating the magnetic field of neutron star that was remained ambiguous due to non-detection of cyclotron line(s) in them. The findings from our work will be discussed in detail in this talk.

Chandrayaan-2 landing site on the Moon: A remote sensing perspective

Date: 2018-04-13
Speaker: Mr. Rishitosh Sinha
Venue: Room 113, Thaltej Campus

Abstract

Size resolved black carbon content of aerosols and its influence on the hygroscopic growth of aerosol

Date: 2018-04-09
Speaker: Bighnaraj Sarangi
Venue: Ground Floor Lecture Hall

Abstract

Aerosols are ubiquitous and undergo a continuous transformation during their residence in the atmosphere. Aerosol generated from gas to particle conversion or condensation of non-volatile vapours on the surface of pre-existing particles is termed as secondary aerosols. Aerosols originated through secondary formation process get activated to cloud condensation nuclei (CCN)and influence aerosol cloud indirect effects. For this, a detailed characterisation of aerosol size, chemical composition and their state of mixing is very much essential. In this seminar observation of nucleation and growth events and identification of aerosol components (e.g. organics or inorganics) responsible for these events, size selective refractory black carbon measurement and determination of their mixing state, and size selective refractory black carbon measurement and their influence over hygroscopic growth of atmospheric aerosols will be discussed.

Formation of gas-phase water in the interstellar medium

Date: 2018-04-09
Speaker: S. Sunil Kumar
Venue: Ground Floor Lecturer Hall

Abstract

One of the major mechanisms by which water molecules are formed in the interstellar medium (ISM) is via a series of ion-molecule reactions in gas phase involving hydroxyl cations and hydrogen molecule. The abundance of water molecules in the ISM is governed by the rate at which these reactions occur. Therefore, the measurements of the rate coefficients of these reactions in the interstellar conditions is crucial to the understanding of the formation of water in the ISM and several related processes. In this talk, I will present the results from the first measurements of the rate coefficients of the reactions relevant to the formation of gas-phase water molecules in the ISM.

Mean horizontal winds for a Vortex system

Date: 2018-04-06
Speaker: Shefali Uttam
Venue: Room 113, Thaltej Campus

Abstract

Constraining black-hole spins with gravitational wave observations

Date: 2018-04-06
Speaker: Dr. Vaibhav Tiwari (Cardiff University, UK)
Venue: Room No. 469

Abstract

Observations of gravitational waves from merging black-hole binaries are beginning to teach us about the population of stellar-mass black holes in the universe. An individual observation allows measurements of the black-hole masses, but only limited information about the black-hole spins, both their magnitude and orientation. Previous work has shown that from multiple signals we can infer the distribution of spin orientations, which allows us to distinguish between formation and evolution scenarios. In my presentation, I will go over some basics of population analysis and will show how by taking into account the variation in the signal strength with spin magnitude, the mass distribution of black holes, and the signal degeneracy between mass-ratio and spin the scenarios can be greatly constrained.

Quantum simulation with ultracold atoms in optical lattices

Date: 2018-04-06
Speaker: Dr. Bodhaditya Santra
Venue: Ground Floor Lecturer Hall

Abstract

Predicting the dynamics of an interacting many-body system is often a challenging task either by an analytical method or by numerical simulation. The way to a faster and more accurate solution was embedded in the vision of Feynman’s quantum computers for universal quantum simulations. Ultracold quantum gases offer unique possibilities to simulate quantum dynamics in a highly controllable and precisely tuneable setup. In this talk, I will present an introduction of the field providing a state-of-the-art picture. Specifically, I will present the results obtained with a rubidium Bose-Einstein condensate loaded in an optical lattice. Using a scanning electron microscope [1], we prepared the initial state and observed “Negative differential conductivity” in an interacting quantum gas [2]. Finally, I will present my future research plan. [1] B. Santra and H. Ott, J. Phys. B. 48, 122001 (2015) [2] R. Labouvie, B. Santra, S. Heun, S. Wimberger, H. Ott, Phys. Rev. Lett. 115, 050601 (2015)

Heavy quarks as probes of longitudinal structure of the fireball in relativistic heavy ion collisions

Date: 2018-04-03
Speaker: Dr. Sandeep Chatterjee ( AGH Univ. Of Science and Tech, Krakow)
Venue: Room No. 469

Abstract

While the transverse dynamics of relativistic heavy ion collisions has been studied in great details, understanding the longitudinal structure and the related breaking of boost invariance along the beam direction is still at an early stage. In this talk, we will discuss our recent proposal of the use of heavy quarks as excellent probe of this forward-backward symmetry breaking.

Recent developments in QCD thermodynamics from HTL effective theory

Date: 2018-03-22
Speaker: Dr. Najmul Haque
Venue: Room No. 469

Abstract

Hard-Thermal-Loop (HTL) perturbation theory is a gauge-invariant reorganization of usual perturbation theory at finite temperature and chemical potential where higher order diagrams contribute to the lower order one. In this talk, I will summarize recent developments in the HTL approach to QCD, specially the study of QCD Equation of State. First I will briefly discuss about the HTL perturbation theory and then I will present the finite-temperature and -density calculation of QCD thermodynamics at NNLO from the HTL perturbation theory. Then I will discuss generalization of the HTL framework including the magnetic scale (g^2T) resummation and also including finite quark masses and finally the results of the second order susceptibility at this two new frameworks.

Heating in solar active regions and the importance of X-ray observations

Date: 2018-03-22
Speaker: Giulio Del Zanna
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

I review a few key observational aspects about how we constrain the heating theories in the cores of active regions. Most of our recent knowledge comes from EUV/UV observations, where very little information on the hot plasma, formed above 3 MK, can be obtained. The soft X-rays around 100 Angstroms are a promising candidate in the future, although important constraints will soon be obtained from X-ray spectroscopy around 10 Angstroms, where measurements of chemical abundances are also possible.

Low Energy Electron Induced Chemistry: A New Frontier in Astrochemistry

Date: 2018-03-21
Speaker: Dr. Daly Davis
Venue: Room No 006, Thaltej Campus

Abstract

Low energy electrons (LEE) can be used as a tool to control chemical reactions at the single molecular level, in gas phase, and in condensed phase. Electron-induced chemical processes at low energies can proceed either via charge transfer followed by electronic excitation of the target, or by the way of dissociative electron attachment (DEA). The DEA process is initiated when the molecule resonantly captures a LEE to form a molecular negative ion (NIR), which is a short-lived electron-molecule compound state. An exciting new aspect of DEA is the possibility of chemical control. The recent discovery of functional group dependence in DEA allows selective bond dissociation (1). Control and selection of chemical reactions using electrons have become more fascinating after it was proposed recently by us that a low energy electron can be used as a catalyst for selective multi-bond breaking reactions (2, 3). This theoretical discovery of formation of neutral molecules by electron catalysed multiple bond breaking mechanism endorse more control over electron induced chemistry. Also, the interest in electron-induced chemistry has recently been renewed by the discovery that low energy electrons play a significant role in damaging and also repairing DNA. Further, there is an increasing realization of its importance in plasma devices and nanolithography. Moreover, electron induced chemistry introduces a new frontier in astro-chemistry. Recent studies identified one hundred eight molecular species in the Interstellar Medium (ISM) through vibrational emission bands (obtained from telescopes such as ALMA) and (sub) millimetre rotational transitions. These species include simplest diatomics (H2 and O2) to complex organic molecules (aldehydes esters, ketones and poly aromatic hydrocarbons). Understanding the mechanism for the formation of such molecules in the ISM opens up the secret of molecular universe. One of the proposed mechanism for the prebiotic synthesis occurs on ice mantles surrounding micron sized dust grains through energetic processors. Recent studies showed that low energy electron can also be an important energy source to initiate this prebiotic synthesis (4). Prebiotic synthesis by low energy electrons can be studied by understanding the chemical reactions through several mechanisms which are active in the low energy regime such as DEA, catalytic electron, excitation and dissociation. Post irradiation interactions inside the ice mantles or inside thick monolayers of films can also shed light on the ISM organic syntheses. For these studies low energy electron collision experiments in condensed phase is one of the ideal situation to stimulate the ISM’s cold (<10K) and empty (>10-12 Torr) environment in laboratory conditions. This talk will focus on astro-chemically relevant LEE induced chemical reactions those we have studied in our laboratories (5, 6) and state of the art design and fabrication of experimental apparatus for LEE-molecule collisions in the condensed phase.

Where did all the sand of the Thar Desert come from?

Date: 2018-03-20
Speaker: Dr. Anirban Chatterjee
Venue: Ground Floor Lecture Hall

Abstract

Deserts with their massive dune fields and vast wilderness have always inspired human imaginations. Understanding origin, evolution, ecology and anthropology of deserts has been a fascinating scientific pursuit. The Thar desert of Indian sub-continent is the 9th largest sub-tropical desert of the world that covers an area over 4000 sq. km. It is located along the eastern most stretch of the great Sahara-Arabian desert system of horse latitudes and hosts a variety of sand dunes. Yet it is one of the most populated deserts of the World. Even the first Indian civilisation developed along its margins. In spite of its apparent geographic and geologic importance, the sources of its sand remain largely speculative. In this context, I will discuss findings of previous studies and our effort using geochemical principles.

Exploration of space using comets as Probes

Date: 2018-03-16
Speaker: Dr. Susarla Raghuram
Venue: Room 113, Thaltej Campus

Abstract

High peak power segmented Bessel beams of tunable range

Date: 2018-03-13
Speaker: Mr. A. Srinivasarao
Venue: Room No 113, PRL Thaltej

Abstract

The credentials of Bessel beam with reference to Gaussian, Hermit Gaussian, Laguerre Gaussian are smallest spot size and long-range non-diffraction. Such properties make the Bessel beams indispensable for a variety of applications including fine alignments of the laser beam, optical power transport and atomic guiding. Typically, the Bessel beams are generated by propagating Gaussian beam through axicons. However, the Bessel beams generated though the conventional techniques have the common drawback of fixed range. Additionally, due to the imperfection in the tip of the axicon, the Bessel beams have intensity modulation in the central lobe along the propagation direction. In this talk, I will discuss our new results on a novel experimental technique of Bessel beam generation using hollow Gaussian beam. Since the hollow Gaussian beam has no intensity at the center, it eliminates the effect of the axicon tip and produce a Bessel beam without wiggling in the intensity distribution along beam propagation. Additionally, using higher order hollow Gaussian order, we showed the control in the range of the Bessel beam. We also observe the increase in the peak intensity of Bessel beam using single-pass second harmonic generation (SHG) in lithium tantalate (MgO:sPPCLT) and lithium niobate (MgO:sPPCLN) crystals. I will also cover the basics of Bessel beams and nonlinear optics.

Model-based analyses of an Ocean acidification mesocosm experiment

Date: 2018-03-13
Speaker: Dr. Shubham Krishna
Venue: Ground Floor Lecture Hall

Abstract

Studies suggest that Ocean acidification (OA) has severe effects on marine phytoplankton. Mesocosm experiments allow investigations on impacts of OA on plankton communities in the vicinity of their natural habitats. Marine ecosystem models serve as an efficient tool to analyze and interpret mesocosm data, as they use mathematical equations to describe processes controlling dynamics of planktonic ecosystems. I will discuss results from a study that investigated effects of OA on phytoplankton growth dynamics by analyzing data from an ocean acidification mesocosm experiment using different model approaches. Applied methods yield the optimized model solutions (with optimised parameter values) that maximize the likelihood probability of models explaining mesocosm data. The model-based data analysis of the experiment suggests that the large variability that was observed in calcification could have been generated due to small differences in initial abundance of coccolithophores during initialization (filling) of mesocosms. The model seems to suggest that OA may enhance carbon fixation rates in phytoplankton, but at the cost of elevated metabolic stress

Beauty of doing science: A rear mirror view

Date: 2018-03-12
Speaker: Prof. A. Jayaraman
Venue: Ground Floor Lecture Hall

Abstract

This presentation is a recollection of my research career in PRL starting from my PhD days. It is also the story of evolution of aerosol studies starting from fundamental measurements to its current relevance to contemporary climate change studies. The beauty of doing science is told in a narrative way, how solving one scientific problem leads to further questions and so on. In parallel it is also the story of evolution of rocket technology in ISRO, from small sounding rockets which could hardly reach 100 km to the present heavy launch vehicles going to outer space.

Floor fractured craters on Moon

Date: 2018-03-09
Speaker: DR. S Vijayan
Venue: Room 113, Thaltej Campus

Abstract

Simultaneous generation of 1D- and 2D- Airy beams and their frequency doubling characteristics

Date: 2018-03-06
Speaker: Dr. Raghwinder Singh
Venue: Room No 113, Thaltej Campus

Abstract

Airy beams, 1D and 2D, are the optical fields with very peculiar properties of non-diffraction, self-healing and self-acceleration. Typically, the optical Airy beams are generated through the Fourier transformation of a cubic phase modulation Gaussian beam. The cubic phase modulation to the Gaussian beam is done using different phase modulators including spatial phase modulator (SLM), cubic phase mask (CPM), non-linear quadratic crystal, and cylindrical lens. However, none of the existing techniques can provide both 1D and 2D Airy beams simultaneously. Here we report on an experimental scheme using a pair of concave and convex cylindrical lenses and some common optical elements available in standard optics lab, producing 1D and 2D Airy beams at same time of high power over a wide wavelength range. The efficiency of our experimental setup for 1D Airy beam generation is more than 80 % and for 2D Airy beam, it is around 70 %, which is much higher than the other techniques, for example, CPM and SLM. We have also studied the frequency doubling characteristics of 1D and 2D Airy beams using a 5-mm-long BIBO crystal. In second harmonic process the power conversion efficiency of 2D Airy beam is higher than 1D Airy beam.

Paleogene sequences of Jaisalmer basin, Rajasthan - a paleoclimate archive

Date: 2018-03-06
Speaker: Dr. Amitava Patra
Venue: Ground Floor Lecture Hall

Abstract

The Jaisalmer basin is the eastern extension of the shelf part of the Indus basin and represents a more or less central part of the "West Rajasthan Shelf" tectonic province that is located to the west of the Aravalli ranges in western India, occupies an area of 42000 sq km and much of it is covered by the modern sand-dunes. Shallow-water sedimentary successions from the Jaisalmer carbonate platform offer a rare opportunity to learn about the Paleocene–Eocene Thermal Maximum (PETM; 55 Ma) and its impact on the shallow-water ecosystems. The PETM representing the extreme warming event in the Cenozoic Era is of particular interest to the Geoscientists since it is considered as an analog to the present climate change. In the studied carbonate samples, the Mn and Sr concentrations and low Mn/Sr ratio (<1) together with the stable and radiogenic isotope data suggest that they are pristine with little diagenetic alterations and have retained their primary isotopic signatures. A prominent negative excursion in δ13C curves of bulk-rock (- 3‰) is interpreted as the carbon isotope excursion during the PETM. Also, the δ18O (-6.4 to -9.3‰), values are very similar to PETM carbonate values in the studied samples.

Inferences of the Deep Solar Meridional Flow

Date: 2018-03-01
Speaker: Dr. Vincent Boening
Venue: USO Seminar Hall

Abstract

The solar meridional flow is a crucial ingredient in modern dynamo theory. Seismic estimates of this flow have, however, been contradictory in deeper layers. Here, we develop and validate a method for computing spherical Born approximation kernels for time-distance helioseismology and we employ these kernels to invert for the deep solar meridional flow using 652 days of GONG data from 2004 - 2012. Above about 0.85 solar radii, our inversions confirm the result obtained by Jackiewicz et al. with the ray approximation regarding the general structure of the flow. This especially concerns a shallow return flow at about 0.9 solar radii, although some differences in flow magnitude are apparent. Below about 0.85 solar radii, we obtain several different results that are consistent with the measured travel times within the measurement errors. While one result is similar to the original single-cell flow found by Jackiewicz et al., the other results exhibit a multi-cell flow structure in the southern hemisphere. To reach an unambiguous conclusion on the meridional flow in this region, the errors in the measured travel times have to be considerably reduced. From this, I conclude that an unambiguous detection of the meridional flow is limited to a much shallower region than previously thought. This is a partial relief to the controversy about measurements of the deep solar meridional flow.

Long-term Trends in Solar Photospheric Fields and Solar Wind Micro-Turbulence

Date: 2018-02-27
Speaker: Prof. S. Ananthakrishnan
Venue: USO Seminar Hall

Abstract

Solar activity has been monotonically decreasing over the past ~ 25 years with each new solar cycle being less active than the previous one. What could this mean in the near term period? We will explore this aspect based on photospheric and heliospheric data.

A very low frequency space-payload to study interplanetary plasma turbulence

Date: 2018-02-27
Speaker: Prof. S.Ananthakrishnan
Venue: USO Seminar Hall

Abstract

At the S.P.Pune University, we are making an effort to put a small tri-axial electric and magnetic space payload in the frequency range from 0.3 to 16 MHz, called SEAPS (Space Electromagnetic And Plasma Sensor) into a L1 or Lunar orbit with multiple objectives. It will serve as a training effort for the University students, as a technology demonstrator and as a tool to investigate the lowest radio frequencies hitherto unopened, to understand solar flares and reconnection mechanisms, as a precursor for a future interferometric mission, etc. We will give a brief description of the efforts.

Filament Dynamics on Small to Moderate Scales

Date: 2018-02-26
Speaker: Dr. Anand D. Joshi
Venue: USO Seminar Hall

Abstract

Sunspot and synoptic science at the World Data Center SILSO

Date: 2018-02-26
Speaker: Dr. Frédéric Clette
Venue: USO Seminar Hall

Abstract

Since 1940, the solar physics team of the Royal Observatory of Belgium has developed a solar station dedicated to synoptic observations of the Sun (photosphere and chromospere). Since 1981, it also runs the World Data Center (WDC) for the sunspot index, a unique 400-year record of solar activity, further expanding its expertise in the long-term monitoring of the solar cycle. We present the evolution and the present capabilities of the Uccle station (USET) and the ongoing digitization of its sunspot drawing and photographic collections. Our production include both near real-time CCD images of the Sun and a new detailed sunspot group catalog covering more than 70 years. Next to our own observations, we also present the recent deep modernization of the WDC SILSO. In particular, we describe the recent end-to-end recalibration of the sunspot and group number series, which led to the release of the first-ever revised version of this unique reference. >From a static data set, the sunspot number has now evolved towards a dynamical data series open to continuous improvements and quality control, back to year 1610. We conclude on our future plans for synoptic ground-based imaging at USET, in coordination with other stations worldwide, and on the continuing improvement to the sunspot number. We will evoke the current and future implications of those new long-term datasets on key scientific issues in solar physics and other disciplines.

1. Radon emission from moon revisited , 2. Sea level fluctuations along Eastern/South-Eastern coast of India

Date: 2018-02-23
Speaker: Prof. Debabrata Banerjee
Venue: Room 113, Thaltej Campus

Abstract

National Nanofabrication Centre: Facilities and collaboration opportunities

Date: 2018-02-22
Speaker: Dr. Y. P. Prabhakara Rao & Dr. Vijayaraghavan
Venue: Room No.113, Thaltej Campus, PRL

Abstract

The Centre for Nano Science and Engineering (CeNSE) was established at the Indian Institute of Science (IISc), Bengaluru to pursue interdisciplinary research on the nanoscale. Activities of interest to the Centre include, materials, electronics, MEMS/NEMS, photonics, biotechnology, and solar cells. CeNSE houses state-of-the art National Nanofabrication Centre (NNfC), Micro and Nano Characterisation Facility (MNCF) and Packaging facility. NNfC is capable of realizing micro and nano scale devices on various substrates including Si, GaN, SiC, quartz, glass, graphene, and III-V. The facility houses industry standard tools geared to realize a wide variety of Semiconductor Devices, MEMS/NEMS, Photonics, Photovoltaics, Microfluidic and Biosensors. MNCF conducts virtually any type of electrical, optical, mechanical and material characterization. Both of these are national user facilities and are accessible to outside researchers.

National Nanofabrication Centre: Facilities and collaboration opportunities

Date: 2018-02-22
Speaker: 1. Dr. Y. P. Prabhakara Rao and 2. Dr. Vijayaraghavan
Venue: Room 113, Thaltej Campus

Abstract

Generation of biphoton orbital angular momentum eigenmodes with asymmetric optical vortex beam

Date: 2018-02-21
Speaker: Mr. Jabir M. V
Venue: Room No 113, PRL Thaltej

Abstract

Quantum entanglement, the quintessential curious phenomenon, shows strong non-classical correlations in joint two separate quantum systems, and plays a crucial role in many important applications in quantum information processing, including quantum communication, quantum cryptography and teleportation. Orbital angular momentum (OAM) entanglement in the biphoton eigenmodes has high potential in the field of quantum communication as it can give high dimensional entanglement between the photon pairs. We report a study of biphoton OAM eigenmodes generated in the spontaneous parametric down-conversion process using asymmetric vortex beam. With the help of spiral phase plate (SPP) we generate the symmetric optical vortex beam. The OAM content for different asymmetry is verified using OAM projective measurements. Using the tailored OAM pump beam we have studied the biphoton OAM eigenmodes in the SPDC process, and shown that one can tune or select the desired eigenmodes by simply controlling the asymmetry in the pump beam. Calculation of Schmidt number(K) of the total OAM Hilbert space spanned by the biphoton modes showed that proper tailoring of OAM in the pump beam will increase the dimensionality of the state.

Chemical and Isotopic Studies of Atmospheric Aerosol: Sources, Deposition Fluxes and Surface Ocean Biogeochemistry

Date: 2018-02-21
Speaker: Mr. A. K. Sudheer
Venue: Ground Floor Lecture Hall

Abstract

Glaciation on Mars: Recent findings

Date: 2018-02-16
Speaker: Mr. Rishitosh K. Sinha
Venue: Room 113, Thaltej Campus

Abstract

Photohadronic process: a novel mechanism to explain the multi-TeV flaring from high energy blazars

Date: 2018-02-15
Speaker: Dr. Sarira Sahu
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Many high-energy blazars (HBLs) are observed flaring in multi-TeV gamma-rays and the emission mechanism is not understood well. The traditional leptonic model has difficulties to explain these emissions. These high-energy gamma-rays get attenuated due to extragalactic background light. So we can't see very-high energy gamma-rays from far-off sources. We have developed a photohadronic model to explain these flarings and are able to explain most of them very well. However, our model prediction depends on the spectral energy distribution (SED) of the synchrotron self-Compton (SSC) photons which is so far not been measured but fitted using leptonic processes. In this talk I shall discuss about few flaring blazars and their interpretation using our model. Also, I shall comment on the importance of observing the photon flux in SSC band by satellite-borne experiments to understand the emission mechanism in blazar jet. This observation will also shed more light on the production of very high energy neutrinos by IceCube and also dark matter in the mass range (few keVs to about 100 MeV).

The Lunar Magma Ocean (LMO) - Myth or Misconception?

Date: 2018-02-09
Speaker: Dr. Dwijesh Ray
Venue: Room 113, Thaltej Campus

Abstract

Astrochemistry 2017 - Where we stand?

Date: 2018-02-09
Speaker: Dr. B Sivaraman
Venue: Room No 006, PRL Thaltej

Abstract

Probing the central engine in Seyfert 1 galaxies

Date: 2018-02-08
Speaker: Dr. Main Pal
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Understanding the nature of the unresolved central engine has reached to a great level in Seyfert 1 galaxies. Though we do not understand actual character of the central engine, we study these sources through timing as well as spectroscopic tools. Using these tools, we investigate them in the multi-wavelength range such as the UV/Optical as well as the X-ray bands. One of the major interest is to understand the UV/Optical emission variability and its connection to the X-ray emission. In this direction, I will be discussing about the recent results on a narrow line Seyfert 1 galaxy NGC 4593 and a broad line Seyfert 1 galaxy 1H 0419-577. In the NGC 4593, I have made a detailed study on strongly correlated UV/Optical/X-ray emission and I found that the real disk may not be as the predicted one Shakura-Sunyaev standard disk. In the 1H 0419-577, the marginally correlated UV/Optical/X-ray emission show a complex origin of the UV/Optical variability possibly a mixture of reprocessing and the changes in the geometry of X-ray emitting corona. I will also present some ongoing work on a NLS1 Mrk 766. This shows moderate harder when brighter state and soft emission is leading to the hard emission.

Generation of optical vortices in mid-IR with the help of optical parametric oscillators

Date: 2018-02-05
Speaker: Mr. Varun Sharma
Venue: Room No: 113, PRL Thaltej

Abstract

Optical parametric oscillators (OPO) have proved their versatility as a source of coherent radiation over a wide range of wavelengths, which is not possible to achieve with conventional Lasers. For example, the mid-IR wavelength range which is also known as fingerprinting region due to the presence of fundamental absorption bands of various molecules and widely used for high resolution molecular spectroscopy, can not be accessed without the use of nonlinear parametric processes and or OPOs. The OPO sources conventionally produce output radiation in Gaussian intensity distribution. However, generating mid-IR radiation in vortex spatial intensity profile, one can extend the advantages of such sources in terms both spectral and spatial parameters. Using a PPLN based OPO we have transferred optical vortices at near-IR wavelength directly to the mid-IR region and produced high power and higher order optical vortices continuously tunable across 2.3 μm to 3.3 μm. In this talk, I will discuss about the generation technique for optical vortices in mid-IR and their characteristics.

XSM payload FPGA RTL code development process and its qualification

Date: 2018-02-02
Speaker: Mr. Arpit R. Patel
Venue: Room 113, Thaltej Campus

Abstract

Characterisation of organic matter source and sediment distribution in Ashtamudi Estuary, southern India

Date: 2018-01-30
Speaker: Dr. Praveen Mishra
Venue: Ground Floor Lecture Hall

Abstract

Modern climate study is essential to develop an understanding of past climate change. The present study is focused on the surface sediments of Ashtamudi Estuary (Kerala, southern India) to understand (i) the fate and sources of organic matter by investigating lipid biomarker (n-alkanes) distribution in modern sediments and vegetation samples; and (ii) the factors controlling the sediment distribution into the lake basin using geochemical approach. A number of n-alkane indices have been calculated to illustrate the variability in space by considering separately the river dominated northern reaches and marine-influenced southern part of Ashtamudi Estuary. The P-aqueous (Paq) and terrigenous/aquatic ratio (TAR) indices demonstrate maximum aquatic productivity (plankton growth and submerged macrophytes) in the tidal dominated region of the Ashtamudi Estuary. The carbon preference index (CPI) and average chain length (ACL) provide evidence for high terrestrial input in the river dominant region, whereas the lower end of the estuary is dominated in high aquatic productivity. The geochemical approach enabled us to delineate natural (fluvial and marine) versus anthropogenic factors in controlling the sediment distribution into the basin.

Characterisation of organic matter source and sediment distribution in Ashtamudi Estuary, southern India

Date: 2018-01-30
Speaker: Dr. Praveen Mishra
Venue: Ground Floor Lecture Hall

Abstract

Investigation of Sun-like G Stars and Their Exoplanets

Date: 2018-01-29
Speaker: Shashanka R. Gurumath

Abstract

Humans' quest is to understand how the universe is originated and has been evolved; how the stars, planets and finally, life is emerged on the Earth? How the Sun and Solar system are formed? Although it is too naive, nebular hypothesis of solar system formation doesn't explains many of these intriguing observations of solar system, especially the angular momentum problem and architecture of solar system, etc. In order to find clues for some of these problems, by employing exoplanetary data, we have carried out a research on understanding the influence of dynamics, chemical abundance and magnetic field structure of Sun-like G stars on the formation and orbital migration of their exoplanets. During this talk, I will also discuss some of the results (possible solution for the faint young sun paradox, missing mass in the vicinity of the sun, etc..,) that are emerged from this study

Orbital Angular Momentum Entanglement - Effect of Turbulence

Date: 2018-01-25
Speaker: Dr. Shashi Prabhakar
Venue: Thaltej campus Room no : 006

Abstract

The orbital angular momentum (OAM) states of photons are suitable candidates for the implementation of quantum systems for use in high-dimensional quantum key distribution. Unlike the polarization of light, which offers a two-level Hilbert space, the OAM of photons provides an infinite-dimensional Hilbert space. The effect of atmospheric turbulence on such high-dimensional OAM entanglement will be presented. The evolution of high-dimensional quantum states in an OAM basis shows that the amount of entanglement between two qutrits does not decay fast compared to higher order OAM state. This is in contrast to the situation that was observed for qubits in weak scintillation. Also to implement quantum teleportation, one needs to perform joint Bell measurements using Hong-Ou-Mandel (HOM) interference. Similar to the prior case, turbulence can cause considerable distortion of optical modes traversing atmospheric channels. In this talk, the effect of turbulence on the HOM interference effect will also be discussed. Under certain conditions, turbulence does not have any effect on the quantum interference of OAM entangled state. This opens up the use for quantum communication and quantum synchronization via free-space communication channels.

Terahertz light emission and detection in graphene-based van der Waals 2D heterostructures

Date: 2018-01-24
Speaker: Dr. Deepali Yadav
Venue: Thaltej campus Room no : 006

Abstract

Graphene has attracted considerable attention due to its massless and gapless energy spectrum. This talk will cover graphene based three different device geometries with experimental evidences of their operation in the THz frequency regime. Dual-gate lateral p-i- n graphene channel transistor (DG-GFET) structure under complementary dual-gate bias and forward drain bias, promotes spontaneous incoherent THz light emission. A laser cavity structure implemented in the active gain area can transform the incoherent light emission to the single-mode lasing. We designed and fabricated a DG-GFET incorporating a distributed feedback (DFB) cavity by using toothbrush-shaped dual-gate metal electrodes. Recently we succeeded in observing broadband (1-7.6 THz range) amplified spontaneous incoherent LED- like emission as well as single mode lasing at the DFB fundamental mode frequency of 5.2 THz at 100K. Asymmetric dual-grating- gate meta-surface structures may promote plasmonic superradiance and/or plasmonic instabilities giving rise to a giant THz gain enhancement at the plasmonic resonant frequencies. Further improvement will be given by a gated double- graphene-layer (G-DGL) nanocapacitor vdW 2D heterostructures. Exploitation of the graphene plasmonics in vdW 2D heterostructures will be the key to realize room-temperature, intense THz lasing.

Mukundpura Carbonaceous Chondrite

Date: 2018-01-23
Speaker: Dr. A. D. Shukla
Venue: Ground Floor Lecture Hall

Abstract

The little chunks of rock and debris in space are called meteoroids. They become meteors or shooting stars when they fall through a planet's atmosphere and leave a bright trail as they are heated to incandescence by the friction of the atmosphere. Pieces that survive the journey and hit the ground are called meteorites. The meteorites, holding immense information of the outer space strike on our planet Earth. However, they are noticed in areas of high human population on the basis of the fireball and the impact on the ground. Mukundpura meteorite is the most recently reported meteorite fall in India. It took place on June 6, 2017 at 5:15 IST, at Mukundpura village in the district of Jaipur, Rajasthan. This is found to be the 6th carbonaceous chondrite type meteorite fall documented in India. Preliminary results will be discussed in the seminar.

On the multiple scale variability of the Disturbance Storm Time (Dst) Index

Date: 2018-01-23
Speaker: Prof. R. Rajaram
Venue: Ground Floor Lecture Hall

Abstract

The origin of the Dst index can be traced to the work initiated by Nanabhai Moos at the Colaba Observatory in the last decades of the nineteenth century. The studies carried out showed that geomagnetic storms started simultaneously at longitudes widely separated but considerable local effects, not attributable to standard diurnal patters, also overlapped. Several methodologies have been developed in the years that followed to understand the global and longitudinal components of the geomagnetic disturbances using methods that were strongly influenced by original philosophy. With the improvement of the geomagnetic Observatory network it became possible to define a uniformly acceptable index for geomagnetic disturbance suitably named as the Disturbance Storm Time index or Dst. Dst has been used almost universally as a global measure of geomagnetic disturbance. It is also used as principal parameter around which the magnetosphere models are built. Over 57 years of continuous and robust data of Dst index is now available and the talk will try to provide a comprehensive view of multiple scale variability of the geomagnetic disturbance recorded over the period.

Impact craters in the vicinity of Valles Marineris on Mars

Date: 2018-01-19
Speaker: Mr. Harish
Venue: Room 113, Thaltej Campus

Abstract

Modeling and analysis of food data to leverage it for nutrition and health

Date: 2018-01-18
Speaker: Dr Ganesh Bagler (Center for Computational Biology, IIIT-Delhi)
Venue: Room No. 469

Abstract

Cooking is central to the identity of Homo sapiens. Starting with a seemingly simple question, ‘Why do we eat what we eat?’, data-driven research conducted from our lab have led to the serendipitous discovery of ‘contrasting food pairing’ in Indian cuisine. Our studies have also revealed ‘culinary fingerprints’ of regional cuisines and role of spice as the molecular fulcrum of Indian recipes. Apart from answering one question, our research has opened up many more questions that are leading us into divergent frontiers of food, nutrition, and health: models for the evolution of recipes, molecular basis of ingredient flavors, emergence of the flavor in a recipe, algorithms for novel recipe generation, fooddisease associations, the therapeutic potential of phytochemicals and strategies forleveraging food as medicine, among others. Through the construction of relevant data resources and hypothesis-driven investigations of food, our data-driven explorations of food have opened a whole new paradigm for food data analytics and show the potential for leveraging food for better health as well as nutrition.

Foraminifera, A key to Quaternary Ocean

Date: 2018-01-16
Speaker: Ms. Nisha Bharti
Venue: Ground Floor Lecture Hall

Abstract

Foraminifera forms major part of ocean microfossils and has served as a good archive for paleo-oceanographic processes for decades. There are ~40,000 species found all over the global ocean. These organisms are sensitive to the changes in the environment where they reside. Foraminifers record variations in oceanic conditions in their calcareous shell. Geochemical and isotopic signature of foraminiferal shells extracted from marine sediments have been extensively used to study paleo-circulation, paleoclimate, paleobathimetry, stratigraphy, coastal pollution and sea level changes. This talk would attempt to explain possibility of deciphering past global ocean circulation and ventilation of water masses in Indian ocean using various planktonic and benthic foram species.

Outgassing Ocean Worlds

Date: 2018-01-12
Speaker: Dr. Apurva Oza
Venue: Room 113, Thaltej Campus

Abstract

Jupiter's icy moon Europa is perhaps one of the most intriguing 'Ocean Worlds' in the Solar System in that recent Hubble Space Telescope (HST) observations appear to suggest a transiently venting saltwater ocean (located ~25 km below the ice). A dusk-over-dawn O2 exospheric asymmetry was also found suggesting a large reservoir of O2 in the ice (Oza et al. 2018), possibly feeding the ocean underneath. In this work we analyze the spectral signatures of oceanic volatiles, possibly present in the O2-dominated exosphere. Recent 3-D Monte Carlo exosphere models when compared with HST observations underestimate the O2 in Europa's corona by a factor of 3, suggesting either plasma-driven or water-driven coronal expansion. Furthermore, the hydrogen predicted by sputtering and sublimation of H2O ice also underestimates the column density of Europa's recently discovered hydrogen corona in Ly-alpha. More generally, Ly-alpha signatures in exoplanetary exospheres have been used as a probe of evaporating ocean worlds (e.g. TRAPPIST-1, Kepler-444). We therefore provide order of magnitude estimates of H2O loss for several candidate ocean worlds, considering several physical mechanisms.

X-ray and radio views of galaxy clusters

Date: 2018-01-11
Speaker: Dr. Viral Parekh
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Galaxy clusters are the most massive bound and quasi-relaxed objects in the Universe. In recent years multiwavelength observations have shown the presence of substructures related to merging events in a high fraction of galaxy clusters. Radio interferometry observations have shown the existence of diffuse large scale emission from the intracluster medium (ICM), suggesting that non-thermal components, magnetic fields and relativistic particles, are mixed with the hot ICM. Currently diffuse radio sources are grouped in two classes. One class is known as radio halos located at the cluster centre and other class is radio relics situated at the cluster periphery. In this seminar, I will talk about our recent findings of new clusters which show varieties of X-ray features, and its corresponding radio observations. I will also talk about the GLEAM (GaLactic and Extragalactic All-sky MWA survey) survey which helps us to investigate new galaxy clusters. GLEAM is a survey of the entire radio sky south of declination +25 deg at frequencies between 72 and 231 MHz made with the MWA (Murchison Widefield Array), the low-frequency Square Kilometre Array (SKA1 LOW) precursor located in Western Australia. Finally I will present some of our results obtained using the upgraded GMRT.

Elemental stoichiometry in the Ocean

Date: 2018-01-09
Speaker: Ms. Deepika Sahoo
Venue: Ground Floor Lecture Hall

Abstract

Around eight decades ago, Alfred C. Redfield established that the plankton elemental composition is similar to the composition of inorganic nutrients in the ocean (C:N:P =106:16:1). This elemental stoichiometric similarity, called as Redfield Ratio, has been the cornerstone in ocean biogeochemistry as it is used to infer ocean biogeochemical processes including the patterns of phytoplankton nutrient limitation and the linkages between different nutrient cycles. Studies based on numerical models, field observations and laboratories have shown variable C:N:P among ocean plankton communities. During the talk, I will discuss the latitudinal variation in stoichiometry in global ocean and the possible mechanisms behind such variation. Multiple nutrient limitation concept will be discussed to understand the optimal stoichiometry of plankton and their different growth phases.

Summer Mesospheric Upwelling and Cooling at High-Latitudes

Date: 2018-01-08
Speaker: Fazlul I. Laskar
Venue: Ground Floor Lecture Hall

Abstract

Although summers are associated with high temperature at the surface of the earth, this is not true for all latitudes and altitudes. Due to dynamical changes, the altitude around summer mesopause (at about 90 km) over high-latitudes is the coldest region in the earth’s atmosphere. Physically, the cooling in the high-latitude mesosphere arises because of the upward motion and associated adiabatic cooling. The experimental quantification of the vertical motion is a challenging task as the expected vertical velocity is of the order of a few cms-1, which is smaller than the typical uncertainties involved in the Doppler velocities derived from atmospheric radars. We have used multistation meteor detections from two VHF-radars in Northern-Norway to measure the wind field and thus gradients, horizontal divergence, and relative vorticity in winds. With these sets of observations the vertical velocities in the summer mesosphere have been quantified. These results would be presented in light of their consequences on other mesospheric phenomena related to summer mesospheric cooling.

The Study of blazars with AstroSat and prospectives in multi-messenger era

Date: 2018-01-04
Speaker: Dr. Sunil Chandra
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The blazars are subclass of Active Galactic Nuclei (AGN), having a bipolar jet of ultra-relativistic plasma oriented very close of our line of sight. Seen at very close angles, the emission from blazars is mostly dominated by the jet. Therefore, the blazars provide a unique sample to understand the acceleration and collimation mechanisms, taking place very close to the central engine. It also enables us the diagnostics of magnetic field, jet morphologies and particle energy distributions. We have been monitoring a sample of bright blazars, utilizing the unique capacity of AstroSat, i.e., the strictly simultaneous coverage from opt/UV to hard X-rays. These observations are mostly co-ordinated with optical/IR observations by ground based observatories, namely MIRO and HCT. During this seminar I aim to discuss a number of interesting results obtained from the studies performed over the course of last two years. The blazar's jet can also be treated as very efficient particle accelerator. The neutrino events are expected to coincide with the flares in blazars. The recent observations by ICECUBE and HAWC have shown some positive hints to this hypothesis, however, still no firm confirmation is obtained. I will also try to discuss the possible contributions of multi-messenger approach to understand the blazar's jet.

Probing the self-couplings of the Higgs boson at the LHC: Current status and future prospects

Date: 2018-01-02
Speaker: Ambresh shivaji
Venue: Room No. 469

Abstract

In the standard model (SM) of particle physics, the Higgs potential depends on two parameters: \mu, the coefficient of the quadratic term and \lambda, the coefficient of the quartic interaction. As a result of the electroweak symmetry breaking, the Higgs potential gives rise to the mass and the self-couplings (trilinear and quartic couplings) of the Higgs boson. Knowing the scale of the electroweak symmetry breaking (v) and the Higgs boson mass (MH), fixes the self-couplings of the Higgs boson completely. However, in presence of new physics affecting the Higgs potential, the predictions for the Higgs self-couplings might change. Therefore, in the light of ongoing searches for new physics signals beyond the SM, it is important that we measure the self-couplings of the Higgs boson independently. In my talk, I will describe direct and indirect methods of probing Higgs self-couplings at the Large Hadron Collider (LHC). I will review the current and future sensitivities towards the measurements of Higgs self-couplings in multi-Higgs production channels, and emphasize the role of the observables and higher-order effects in achieving a better sensitivity at the LHC.

2017

Holocene floods in the middle Satluj valley and their climatic implications

Date: 2017-12-27
Speaker: Ms. Shubhra Sharma
Venue: Ground Floor Lecture Hall

Abstract

Projections based on the climate change scenario predict increased frequency and/or increased magnitude of floods in the Himalayan region due to more intense and frequent coupling between the Indian Summer Monsoon (ISM) and the mid-latitude westerlies. In view of this, studies pertaining to the geological evidence of extreme hydrological events (paleo-floods) become important as these extend beyond the instrumental records and ensure better understanding of the river response to the climate variability. The Satluj River in the north-western Himalaya is frequented by devastating floods in the recent past thus suggesting its sensitivity towards extreme hydrological events. We studied the sedimentary records of palaeofloods in the middle Satluj which has preserved around 27 flood events of increasing magnitude. The geochemical fingerprinting (based on CIA) indicates that the floods were generated in the Higher Himalayan Crystalline with contribution from the trans-Himalaya. Optical chronology allowed us to constrain the floods into four major clusters (viz. 13-11 ka, 8-5 ka, ~4 ka and <2 ka). Climatically, these clusters represent the transitional climatic conditions during the Holocene and are contrary to the earlier studies where intensified Indian Summer Monsoon (ISM) was implicated for the floods in the Himalaya. In this presentation, I would be giving a broad overview of the existing studies on paleo floods in the Indian Himalaya, with an emphasis on the causes of Holocene floods in the middle Satluj valley and their implications towards understanding the synoptic scale coupling (Arctic and North Atlantic Oscillation).

Non-equilibrium spin dynamics of interacting quantum systems

Date: 2017-12-21
Speaker: Dr. Manan Vyas (Instituto de Ciencias Físicas, UNAM, MEX-62210 Cuernavaca, Morelos, Mexico)
Venue: Room No. 469

Abstract

We analyze relaxation dynamics of the survival probability and information entropy of a many-particle fermionic (bosonic) system in a mean-field, quenched by a random two-body interaction (preserving many-particle spin) as a function of spin degrees of freedom. The system Hamiltonian is represented by an embedded Gaussian orthogonal ensemble (EGOE) of random matrices (for time-reversal and rotationally invariant systems) with one plus two-body interactions for fermions (bosons). A simple general picture, in which the spectral variances play a central role, is achieved for describing the short-time spin dynamics of the survival probability and information entropy.

Did life originate in ocean-ridge settings?

Date: 2017-12-19
Speaker: Dr. Alik Sundar Majumdar
Venue: Ground Floor Lecture Hall

Abstract

Recent investigations demonstrate that life most likely have originated in the deep ocean when H2 reacted with CO2 to form CH4 via Fischer-Tropsch reaction mechanism. Although it is established that concentration of CO2 was high in the Archean (4-2.5 Ga) ocean water, uncertainty remained on the process of H2 generation in the early Earth. Following this, I will show an example of geosphere (rock) - hydrosphere (water) interaction predominantly at ocean-ridge settings, which has the potential to release H2 as reaction product. Using a combination of natural observations, experimental studies and numerical modeling, I will present how the chemistry of the interacting fluid can influence the reaction products and also how temperature plays an important role on controlling the amount of H2 generation during such process. This study may therefore provide an insight on the origin of life in the early Earth.

Emergent quantum heat pump in a driven quantum gas

Date: 2017-12-13
Speaker: Dr. Arko Roy (Max Planck Institute for the Physics of Complex Systems, Dresden, Germany)
Venue: Room No: 469

Abstract

We propose a novel scheme for quantum heat pumps powered by rapid time-periodic driving. We focus our investigation on a system consisting of two coupled driven quantum dots in contact with fermionic reservoirs at different temperatures. Such a configuration can be realized in a quantum-gas microscope. Theoretically we characterize the device by describing the coupling to the reservoirs using the Floquet-Born-Markov approximation.

Paleoclimate reconstruction using high altitude lake sediments

Date: 2017-12-12
Speaker: Mr. Abdur Rahman
Venue: Ground Floor Lecture Hall

Abstract

Lake sediments form an important archive to study paleoclimate and paleobiological condition in the continental interior. Stable isotopic composition of carbon and nitrogen in organic matter of the lake sediment provide an important insight into the paleovegetation and nutrient conditions. However, reconstruction of paleotemperature and paleoprecipitation in high altitude environment lacking in situ calcite formation remains challenging. Oxygen isotopes measurement of diatoms using laser fluorination technique in lake sediments has the potential to provide a robust proxy for the same. During this talk, I will explain the methodology, its importance and analytical challenges regarding this technique along with preliminary results of carbon isotopic composition in organic matter from a sediment core in a Himalayan lake.

Gearing up for India's Large Optical-NIR Telescope

Date: 2017-12-06
Speaker: Prof. Padmakar Parihar
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Recently install 3.6m DOT telescope and forthcoming TMT would not be enough to cater the need of growing Indian astronomical community. Access to 10 - 12m size optical-NIR telescope equipped with state of the art back-end instruments can bridge the gap between DOT and TMT. A telescope of this size is only possible when primary mirror is made of smaller mirror segments. The participation into TMT project has given us an opportunity to adopt some the key technologies linked with segmented mirror telescope(SMT) and make use of resources being developed for this mega project within India. In my talk I will present the possible sites for the proposed telescope, preliminary opto-mechanical design and some R&D effort happening in IIA to explore SMT technology by developing a prototype segmented mirror telescope.

Novel quantum phases of ultracold bosonic atoms in optical lattices

Date: 2017-12-05
Speaker: Dr. Kuldeep Suthar
Venue: Room no:469

Abstract

Ultracold atoms provide a novel route to exotic quantum phases of matter. In particular, phases which display coexistence of different types of order. For example, can a solid be superfluid? The quest for this state has been one of the grand challenges in condensed matter physics and dates back to the first prediction of supersolid in $^{4}$He. Supersolidity combines superfluid properties with long-range spatial periodicity of solids. Recent experiments have reported the observation of characteristic signatures of this phase in ultracold quantum matter. To study various quantum phases and their transitions we employ Gutzwiller mean-field approximation in extended Bose-Hubbard model. In this talk, we shall discuss the phase diagram, the effect of synthetic magnetic field on phases and stability of supersolid phase in the presence of long-range interactions.

Disparity of Larmor's formula with energy-momentum conservation

Date: 2017-11-30
Speaker: Dr. Ashok Kumar Singal (PRL)
Venue: Room No. 469

Abstract

The well-known Larmor's formula, which yields power losses of a radiating charge proportional to the square of its acceleration, is not compatible with energy-momentum conservation. In fact, the radiative loss picture derived from Larmor's formula is not consistent with the special theory of relativity. One needs to clearly distinguish between the rate of energy-momentum being carried away by the electromagnetic radiation and that of mechanical energy-momentum losses being incurred by the radiating charge. In literature both power rates are treated as not only equal but almost synonymous. This 100-year old oversight is due to a mathematical subtlety that has been missed in the applicability of Poynting's theorem.

A hybrid setup for fundamental unknowns using T2HK and $\mu$-DAR

Date: 2017-11-28
Speaker: Dr. Monojit Ghosh (Tokyo Metropolitan University)
Venue: Room No. 469

Abstract

Neutrino mass hierarchy, CP-violation, and octant of $\theta_{23}$ are the fundamental unknowns in neutrino oscillations. In order to address all these three unknowns, we study the physics reach of a setup, where we replace the antineutrino run of T2HK with antineutrinos from muon decay at rest ($\mu$-DAR).

A discussion on controls on the Quaternary glaciation in the NW Himalaya

Date: 2017-11-28
Speaker: Dr. Shubhra Sharma
Venue: Ground Floor Lecture Hall

Abstract

Himalayan glaciation show inter-regional variability on centennial to multi-millennial timescales where the glaciers are fed by two major weather systems ‒ the Indian summer monsoon (ISM) and the mid-latitude westerlies. It is suggested that the terrain that lies in the influence of mid-latitude westerlies (NW Himalaya) should respond in accordance with the northern latitude glaciation, where as those that are located in ISM dominated region (central/eastern Himalaya) should be modulated by the winnowing and waxing of the ISM. In addition to this, there is also suggestion that glaciers located in the orographically shielded region (Trans Himalaya) are sensitive to the precipitation changes whereas those in the trajectory of the ISM are temperature sensitive. In order to understand the pattern of glaciation in the Himalayan region, one need to take into consideration, the above variability that is further modulated and controlled by the Himalayan topography and local factors. In the presentation, I would be giving an over view of the current understanding of late Quaternary glaciation in Himalaya along with presenting our studies from the Nubra (Siachin), Zanskar and Sarchu plain in the westerlies dominated NW Himalaya

Lepton Non-Universality and recent excitements in Flavour physics

Date: 2017-11-23
Speaker: Dr. Debjyoti Bardhan (TIFR, Mumbai)
Venue: Room no:469

Abstract

While the Standard Model (SM) has so far proved to be extremely robust and no concrete evidence of New Physics has been found, certain recent measurements relating to B-meson decays have shown tantalising hints of deviation from the SM expectations. In this context, many claims of NP have been made. I will discuss both the neutral and charged current decays of the B-meson, highlighting the different deviations observed, and then describe a model-independent approach to New Physics, based on our papers.

FRB121102 : First detection across 4 - 8 GHz, spectral and polarization properties

Date: 2017-11-16
Speaker: Dr. Vishal Gajjar
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Fast Radio Bursts (FRBs) are some of the most energetic and enigmatic events in the Universe. The origin of these sources is among the most challenging questions of modern-day astrophysics. Thus, it is imperative to understand the properties of these bursts across a range of radio frequencies. Among the known FRBs, FRB121102 is the only source known to show repeated bursts [Spitler et al., Nature, 531, 7593 202-205, 2016], which can allow a detailed investigation of various origin models. In August 2017, we initiated a campaign observing FRB 121102 using the Breakthrough Listen Digital Backend with the C-band receiver at the Robert C. Byrd Green Bank Telescope (GBT). We recorded baseband voltage data across 5.4 GHz of bandwidth, completely covering the C-band receiver's nominal 4-8 GHz band [MacMahon et al. arXiv:1707.06024v2]. The recorded data were searched for dispersed pulses consistent with the known dispersion measure of FRB 121102 (557 pc/cm^3) using high-speed GPU software tools. We detected 21 bursts above our detection threshold of 6 sigmas in the first 60-minutes, out of which 18 occurred in the first 30-minutes only. To our knowledge, this is the highest event rate seen for FRB121102 at any observing frequency. These observations are the highest frequency and widest bandwidth detection of bursts from FRB 121102 (or any other FRB) obtained to-date. We note that individual bursts show marked changes in spectral extent ranging from hundreds of MHz to several GHz. We have used high frequency dynamic spectra of these bursts to estimate the characteristic scintillation bandwidth and correlation time-scale. We also found distinctive temporal structures, separated by a few milliseconds, in three of the strongest bursts, with each sub-structure exhibiting varied spectral features. We will discuss our findings and how these detections of FRB 121102 around 8 GHz opens up a new regime in scrutinizing various origin models. We will also highlight the unique capabilities of the Breakthrough Listen instrument at the GBT which allowed such sensitive and detailed observations.

EXPERIMENTAL HIGH ENERGY ASTROPHYSICS

Date: 2017-11-14
Speaker: Dr. P. R. Vishwanath
Venue: Room No. 469

Abstract

I give a historical perspective of the experiments in gamma ray detection conducted in India.

Rajmahal and Sylhet Traps Revisited

Date: 2017-11-14
Speaker: Prof. J. S. Ray
Venue: Ground Floor Lecture Hall

Abstract

Solid state laser systems for precision measurement and advanced sensing

Date: 2017-11-09
Speaker: Dr. Manasadevi P Thirugnanasambandam
Venue: Room No: 470, 4th floor

Abstract

Solid state laser research has been of interest for decades due to the pace at which new light sources have been identified over the years. The new spectral properties, robustness, compactness, low noise, high–power and reduced costs have all been reasons for the continued interest in the development and deployment of solid-state lasers. In my talk, I will be discussing some of the work that I have done pertaining to the basics of building novel laser sources and also building optical systems for specific applications like ultra-high precision measurement in laser interferometric gravitational wave detectors (LIGO), molecular spectroscopy and trace gas sensing.

A comprehensive study of open clusters

Date: 2017-11-02
Speaker: Dr. Devendra Bisht
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Our main aim is to study the astrophysical behaviour of poorly studied open star cluster NGC 5617 towards, longitude (l) = -45 deg in the Galactic plane using PPMXL, 2MASS, VVV survey, WISE and GLIMPSE data. We also have studied the mass function and dynamical state of the clusters Berkeley 24 and Czernik 27 using the optical CCD data for the first time. Mass function is derived by considering the corrections of data incompleteness and field star contamination. The mass function in the outer region of clusters are found to be steeper than in the inner region, indicating the presence of mass-segregation effect.

PLANCK vs LSS : Tension and solutions

Date: 2017-10-18
Speaker: Dr. Arindam Mazumdar (Physical research laboratory, Ahmedabad)
Venue: Room No. 469

Abstract

Primordial perturbations generated at the time of Inflation is expected to produce the fluctuations in CMB as well as the large scale structures(LSS) of the universe.Standard LambdaCDM theory is expected to describe these CMB observations and LSS observations under a single theoretical framework. However,some recent observations have pointed out some tensions between these two types of observations under LambdaCDM theory. In this talk I will cover some earlier attempts to resolve these tensions.Then I will describe our attempt with viscous cold dark matter to resolve the problem.

Correlation effects in strong field enhanced ionization of molecules : A time-dependent generalized-active-space configuration-interaction study.

Date: 2017-10-12
Speaker: Dr. Siddhartha Chattopadhyay (Max Planck Institute for Nuclear Physics, Heidelberg, Germany)
Venue: Room No. 469

Abstract

In this talk, I will present recent results on the correlation effects in strong field ionization of diatomic molecules. In this work, we have studied $\mathrm{H}_2$, $\mathrm{LiH}$, and $\mathrm{HF}$ molecules, aligned collinearly with the linear polarization of the external field.To elucidate the possible role of electron correlation in the enhanced-ionization (EI) phenomena we consider different levels of approximation with the time-dependent generalized-active-space configuration-interaction (TD-GASCI) method. The results of our studies show that correlation is important and they also demonstrate significant deviations between the results of the single-active-electron approximation and more accurate configuration-interaction methods.We will further investigate the role of low-lying excited states in the EI phenomena. With the inclusion of correlation we show strong carrier-envelope-phase effects in the EI of the asymmetric heteronuclear $\mathrm{LiH}$ molecule. The correlated calculation shows an intriguing feature of cross-over in enhanced ionization with two carrier-envelope-phases at criticalinter-nuclear separation.

Deep learning in astronomical research

Date: 2017-10-12
Speaker: Mr. Vaibhav Dixit
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Artificial Intelligence (AI) is the capability of the machines to perform a task intelligently like humans. Deep learning is a subset of AI which takes inspiration from model of human brain. It is based on neural networks with several layers of nodes. Deep learning encourages computational models that are built on multiple layers to learn representations of data with multiple levels of abstraction. It has surpassed the human performance in several trivial tasks like image recognition and segmentation as well as found applications in various commercial activities like self-driving cars, stock market prediction, cancerous tissue identification and production line performance etc. Given the sheer magnitude of projects undertaken by various organizations, we would end up having Petabytes of data, and no manpower to go through all of them manually. Under such a scenario, we would need intelligent systems which can devour large data. Higher dimensionality of the data, no prior knowledge of the data generation process, low signal to noise ratio and missing information are some other limiting factors in analysis done by humans. However deep learning overcomes these challenges and can open new avenues for scientific research. Deep learning is going to change the way we do science. The talk will focus on some areas of applications of deep learning in astronomy.

Control in open quantum systems out of equilibrium

Date: 2017-10-09
Speaker: Dr. Victor Mukherjee ( Weizmann Institute of Science, Rehovot, Israel)
Venue: Room No:469

Abstract

Control in open quantum systems out of equilibrium is necessary to achieve various tasks, ranging from efficient cooling or heating of the systems, controlling decoherence in open quantum systems, to engineering quantum technologies, such as quantum heat engines and quantum probes. I will talk about control in quantum systems out of equilibrium in presence of Markovian and non-Markovian baths, as well as use of control in quantum technologies.

MLT wave dynamics due to tropospheric convection and solar flux variation

Date: 2017-10-09
Speaker: R. P. Singh
Venue: Ground Floor Lecture Hall

Abstract

The Earth's upper atmosphere is influenced by the incoming solar radiation from above and upward propagating atmospheric waves that originate in the lower atmosphere. Mesosphere Lower Thermosphere (MLT) region is that part of the upper atmosphere where most of the atmospheric waves deposit their energy and momentum affecting the overall structure and composition of the region. For this study of MLT wave dynamics, data from the in-house built passive remote sensing techniques are made use of. These optical remote sensing techniques are in a continuous mode of operation from Gurushikhar, Mt. Abu since 2013. New insights have been obtained by the analyses of these long-term observations of mesospheric nightglow emission intensities (O2 and OH) and temperatures. Some of the recent results, which deal with the solar and atmospheric influences in the MLT region, and vertical coupling of atmospheres during tropical cyclone will be discussed.

Long term X-ray variability of Be/X-ray binaries : a case study of EXO 2030+37

Date: 2017-10-03
Speaker: Prahlad Epili
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

In X-ray astronomy, the study of X-ray binaries shows interesting features of the stellar X-ray sources. Among these the spectacular variability seen in High mass X-ray binaries (HMXBs) at different time scales can be studied to understand the nature of the two stellar components, the physics of matter at extreme physical conditions, the ‘accretion’ process governing the mass transfer to the compact object etc. Majority of these HMXBs are bright and transient in nature. One such class of bright X-ray transients are Be/X-ray binaries. In theses sources, an abrupt accretion of huge amount of matter from the normal star onto the neutron star is seen with X-ray outbursts, i.e an enhancement in the X-ray emission. Study of these X-ray outbursts (some are periodic and some are aperiodic) forms an important basis to further our understanding of these sources. EXO 2030+375 is a transient Be/X-ray binary system. It has been caught in X-ray outbursts numerous times during 19962011 in the RXTE era. We have studied the decade long X ray observations of this binary to understand its long term X-ray variability. The details of the study will be presented.

Novel phenomenological features of neutrinophilic two Higgs doublet model

Date: 2017-09-28
Speaker: Dr. Soumya Sadhukhan (Physical research laboratory, Ahmedabad)
Venue: Room No. 469

Abstract

Decay of active neutrinos is one of the possibilities that can explain the depletion of the neutrino flux detected in the IceCube experiment at an energy around the PeV scale.Here we explore the decay of neutrinos and subsequent decrease in neutrino count in the framework of a neutrinophilic two Higgs doublet model (2HDM). It is also discussed how the non standard interaction (NSI) of neutrinos can arise in a modified neutrinophilic 2HDM scenario. There are also comments on various theoretical and experimental constraints that can affect the explanation of these phenomenological features.

On the occurrence of afternoon reverse jet over Indian longitudes during June solstice in solar minimum

Date: 2017-09-27
Speaker: Kuldeep Pandey
Venue: Ground Floor Lecture Hall

Abstract

In day time, a strong jet of current flows at ~105 km altitude within +/- 3deg latitudes with respect to the geomagnetic equator. In general, this current is eastward and known as equatorial electrojet. However, on many occasions, the flow of current is reversed (westward) and conventionally known as counter electrojet (CEJ). Whether CEJ is generated locally or it is part of global current system is an unsettled issue. The strength of this ionospheric current primarily depends on solar quiet (Sq) electric field and electrical conductivity. In general, it is found that, over the Indian sector, the occurrence of CEJ events in afternoon hours is frequent during June solstice in solar minimum years. Though several mechanisms were proposed earlier, those works did not consider the effects of temporal variations of Sq electric field due to paucity of systematic measurements over the Indian sector. Therefore, an investigation is carried out using the equatorial electrojet model developed in PRL, temporal variations of Sq electric field available in recent times and other inputs. The investigation brings out the explicit role of Sq electric field in generation of afternoon CEJ events, indicating these CEJ events to be a part of global current system. Further, the findings of this investigation are substantiated through various other observations from the Indian sector.

Setting Initial Conditions for Inflation with Reaction-Diffusion Equation

Date: 2017-09-21
Speaker: Mr. Arpan Das (Institute of Physics, Bhubaneswar)
Venue: Room No. 469

Abstract

We discuss the issue of setting appropriate initial conditions for inflation. Specifically, we consider natural inflation model and discuss the fine tuning required for setting almost homogeneous initial conditions over a region of order several times the Hubble size which is orders of magnitude larger than any relevant correlation length for field fluctuations. We then propose to use the special propagating front solutions of reaction-diffusion equations for localized field domains of much smaller sizes. Due to very small velocities of these propagating fronts we find that the inflaton field in such a small field domain changes very slowly, contrary to naive expectation of rapid roll down to the true vacuum. Continued expansion leads to the energy density in the Hubble region being dominated by the vacuum energy, thereby beginning the inflationary phase. Our results show that inflation can occur even with a single localized field domain of size much smaller than the Hubble size. We discuss possible extensions of our results for different inflationary models, as well as various limitations of our analysis (e.g. neglecting self gravity of the localized field domain).

Trace gases over the Bay of Bengal during monsoon season

Date: 2017-09-18
Speaker: Dr. Girach Imran
Venue: Ground Floor Lecture Hall

Abstract

Our study of trace gases (ozone, carbon monoxide and methane) over the Bay of Bengal (BoB) fills a gap of observations during the summer monsoon season, providing information on the extent of seasonal variability over the BoB. Measurements were carried out as a part of the Continental Tropical Convergence Zone (CTCZ) campaign during the summer monsoon season of 2009. The correlated variations of these trace gases and percentage residence time of air parcels over the Indian regions suggest that the enrichment of ozone and precursor gases over the BoB is associated with both emissions and photochemistry over the Indian region. An analysis of modeled ozone along air mass trajectories show mean en-route ozone production rate of about 4.6 ppbv day-1 in the outflow towards the BoB. In situ observations also confirm similar magnitude of en-route ozone production. The low-ozone events coincided with intense rainfall over the BoB. After analysing the observed variability in air temperature, model simulations of vertical winds, and an ozone-profile case study from southern India, we suggest that first low-ozone events were due to strong downdrafts of ozone-poor air masses. While horizontal advection transports the ozone-rich air masses over the BoB. I will emphasize some of the important results during the presentation.

Reactive Oxygen Species (ROS) generation capacity of ambient aerosol over a semi-urban and a high altitude site

Date: 2017-09-12
Speaker: Mr Anil Patel
Venue: Ground Floor Lecture Hall

Abstract

Aerosol are known to exhibit large temporal and spatial variability, which causes large uncertainty in assessing aerosol effects on air quality and climate. Further, aerosol are increasingly recognized for the production of Reactive Oxygen Species (ROS) in their ambience and thus affect oxidative capacity of the atmosphere, and also human health on inhalation. This presentation will discuss the characteristics and ROS generation capacity of ambient aerosol collected over a semi-urban site (Patiala) and a high-altitude site (Mount Abu).

Non-classicality of twisted photons generated by parametric down-conversion

Date: 2017-09-08
Speaker: Mr. Nijil Lal C K
Venue: Room No: 469

Abstract

Photon is the most popular qubit candidate in quantum information processing. Single photon sources have applications in various quantum cryptographic protocols and they have gained more importance over the years with the discovery of an infinite dimensional OAM (Orbital Angular Momentum) degree of freedom. We study the statistics of a heralded single photon source generated in spontaneous parametric down-conversion by looking at its second order optical coherence. In this talk I will discuss the non-classical nature of the heralded single photon source. I will also discuss the observed variation in non-classicality of the source when it is carrying OAM.

Gravity, Thermodynamics and Null Surfaces

Date: 2017-09-07
Speaker: Dr. Sumanta Chakraborty
Venue: Room No: 469

Abstract

In the first part of my talk I will discuss the variational principle for general relativity and some associated subtle facts not shared by other interactions present in nature. In particular null surfaces play a very interesting role throughout the development of general relativity on which I will elaborate upon. A brief idea of black hole thermodynamics and Hawking effect will also be provided. In the second part of my talk, I will discuss the thermodynamics of null surfaces. In particular, I will show that three different projections of gravitational momentum related to an arbitrary null surface in the spacetime lead to three different equations, all of which have thermodynamic interpretations. The implications will be discussed.

Recent Developments in Electronic Subsystems of PARAS

Date: 2017-09-07
Speaker: Mr. J. S. S. V. Prasad
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

PRL Advanced Radial Velocity Abu Sky Search (PARAS) is a high-resolution Spectrograph which uses radial velocity technique for detection of exoplanets. In order to reach an accuracy of Doppler shift measurements of a few meters-per-second, effective temperature regulations of the stellar spectrograph is very important. A change of 1°C in the spectrograph temperature can produce instrument shift of 100m/s due to change in refractive index in Lenses and other optical components. Hence temperature variation during the observation should be within 0.01°C to 0.005°C to get a system stability of 1m/s or better. In this talk, I will discuss about the Temperature controller of PARAS along with some recent developments in other electronics sub systems.

Monitoring atmospheric Greenhouse gases and secondary organic aerosols over India and Southeast Asia

Date: 2017-09-05
Speaker: Dr. Tania Guha
Venue: Ground Floor Lecture Hall

Abstract

According to WRI, 2013 India contributes 6.43% to the total GHGs emission and 2/3 of national burden comes from urban area. Thus monitoring GHGs over urban area is essential. During 2008-2011, mixing ratio and delta-13-C of atmospheric CO2 was monitored at an urban station in India and revealed possible anthropogenic sources. Similar temporal variability has also been observed in atmospheric CH4 concentration over India. The impact of seasonal wind patterns on CH4 variability are analyzed using 3-dimentional model-simulated CH4. The atmospheric budgeting of N2O is more complicated due to little variability in its observation. During 2013-2015, delta-15-N, delta-18-O and site-preference (SP) values of atmospheric N2O was monitored over a semi-urban station at west Pacific island. The station captured anthropogenic signal and stratospheric intrusion. The atmospheric NOx has increased drastically in last few decades and has implications on air quality. The conversion of NOx to aerosol nitrate makes it suitable for studies the NOx precursors as well as its formation pathways. We carried out nitrates aerosol sampling from high-mountain station in west Pacific island during 2010. The objective of our study is to identify sources of NOx for the nitrate-phase in aerosol and understand the nitrate formation pathways from its precursor-NOx.

TBA

Date: 2017-08-31
Speaker: Dr. Uma Shankar Gupta (University of Allahabad)
Venue: Room No. 469

Abstract

TBA

In situ 1.2m telescope mirror aluminizing facility at Mount Abu

Date: 2017-08-31
Speaker: Mr. S. N. Mathur
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Mirrors used in astronomical telescopes are one of the primary components of their optical system. Aluminum coated mirrors used in telescopes are exposed to the local environment, and as a result, mirror surface degrades over the time. The degradation leads to decrease in reflectivity and increase in light scattering and infrared emissivity. In order to achieve better reflectivity, mirrors are routinely re-coated. The aluminization of mirrors is a delicate process as it involves the handling of big optical system. Therefore, it is always better to have an in-situ mirror coating plant. For our 1.2m telescope at Mt. Abu, we have an in situ mirror aluminizing facility. In this talk I shall describe the aluminization process and the facility.

Near-IR Imager Spectro Polarimeter (NISP) electronics Development

Date: 2017-08-28
Speaker: Ms. Deekshya Roy Sarkar (PRL, Ahmedabad)
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Near-IR Imager Spectro Polarimeter (NISP) with H2RG detectors is being developed as a back-end instrument for the upcoming 2.5m telescope at Mt Abu. In this talk, I shall discuss about the two approaches (discrete and ASIC based) that we have adopted for developing the front end electronics of the instrument. I shall also talk about the advantages and performance characteristics, and the work done so far.

A glimpse of quantum Hall physics for optically trapped Bosons

Date: 2017-08-24
Speaker: Dr. Sukla Pal
Venue: Room No:469

Abstract

Emergence of quantum Hall states in cold atoms recently has captured much attention. In this seminar, I will present few basic aspects to implement quantum Hall states for Bosons trapped in optical lattice. Considering Bose Hubbard model (BHM), I will describe the behavior of interacting Bosons in an optical lattice subjected to a synthetic magnetic field where the system can have a possibility to enter into the quantum Hall regime. In presence of random local impurities, the equilibrium phase diagram differs from clean one – - a new gapless phase-Bose glass phase appears as an equilibrium solution of disordered BHM.

A novel spontaneous $CP$ nonconservation

Date: 2017-08-17
Speaker: Dr. Gauhar Abbas (PRL

Abstract

A new type of spontaneous $CP$ breaking in a class of models will be discussed. Consequences of spontaneous $CP$ breaking (in this class of models) are non-trivial for fine-tuning of the standard model Higgs mass, the strong CP problem, neutrino masses, dark matter and baryogenesis. An explanation for recently observed anomalies in the transitions b-> sll and b-> c l \nu is obtained naturally.

Neutrino Astronomy with IceCube Neutrino Detector

Date: 2017-08-17
Speaker: Dr. Debanjan Bose
Venue: Room - 113/114, Thaltej Campus

Abstract

IceCube is a cubic-kilometer neutrino observatory buried deep in the ice sheet at the geographic South Pole. A total of 5160 Digital Optical Modules (DOMs) are deployed on 86 strings forming a three dimensional detector array. Over the past decade, South Pole has emerged as a leading site for neutrino astronomy, particle astrophysics and neutrino physics. IceCube's discovery of a diffuse flux of astrophysical neutrinos started a new era of neutrino astronomy. In this talk I will describe IceCube neutrino detector and some of it's results. Also, I will give an overview of plans to upgrade IceCube.

Impurity textures in a Chern insulator

Date: 2017-08-10
Speaker: Mr. Vibhuti Bhusan Jha (SAC)
Venue: Room No. 469

Abstract

Chern insulators arguably provide the simplest examples of topological phases. They are characterized by a topological invariant and can be identified by the presence of protected edge states. A local impurity in a Chern insulator induces a twofold response: bound states that carry a chiral current and a net current circulating around the impurity. This is a manifestation of broken time reversal symmetry and persists even for an infinitesimal impurity potential. To illustrate this, we consider a Coulomb impurity in the Haldane model. We show that an infinitesimal impurity strength suffices to create bound states. We find analytic wave functions for the bound states and show that they carry a circulating current. Both the cases of trivial and non trivial topology has been considered. In the many-body problem of the Haldane model at half-filling, we use a linear response approach to demonstrate a circulating current around the impurity. Impurity textures in insulators are generally expected to decay exponentially; in contrast, this current decays polynomially with distance from the impurity. Going beyond the Haldane model, we consider the case of coexisting trivial and nontrivial masses. We find that the impurity induces a local chiral current as long as time-reversal symmetry is broken. However, the decay of this local current bears a signature of the overall topology—the current decays polynomially in a nontrivial system and exponentially in a trivial system.

Collision (de)excitation of molecules in Interstellar medium : NH as a case study

Date: 2017-08-10
Speaker: Mr. Ragav Ramachandran
Venue: Room No. 006, PRL Thaltej

Abstract

NH and ND molecules play a very crucial role in the prestellar chemistry as they act as intermediate during the formation of the ubiquitous ammonia. Hence there is a need for the accurate modelling of their abundances in space to better understand the physical conditions and the chemical evolution of the prestellar core. We consider H2 and He as the colliding partners as they are dominant species in the interstellar medium and significantly contribute to the excitation of both NH and ND. The earlier studies on the NH-He system were performed using a potential energy surface (PES) which was proved to be relatively close. However, they did not consider the vibration of the NH bond which can impact the magnitude of the collisional data. Hence we take into account the vibration of the N-H molecules.We are also working on the NH-H2 system and preliminary rate coefficients which are first of its kind. These results would be of particular interest because they are first for this system and they should contribute significantly impact the astrophysical modelling by allowing an accurate determination of the NH abundance in the space.

Radioactive sources of APXS on-board Chandrayaan-2: Implications

Date: 2017-08-10
Speaker: Mr. Mithun N. P. S.
Venue: Room - 113/114, Thaltej Campus

Abstract

Alpha Particle X-ray Spectrometer (APXS) experiment on-board Chandrayaan-2 rover employs the techniques of X-ray Fluorescence (XRF) and Particle Induced X-ray Emission (PIXE) to measure the elemental abundances of Lunar surface close to the landing site. For this purpose, APXS carries six Cm-244 sources of total activity of 30 mCi, which emits X-rays as well as alpha particles. Usage of these high activity sources calls for certain special considerations in the design of the instrument, assembly, characterization and calibration, transportation and spacecraft level integration tests to ensure the safety of people around and better performance of the instrument. In this talk, we will discuss the aspects of radiation safety, radiation dose calculations, measurements, and limits, transportation regulations etc in the context of APXS.

Searching for top squark in the compressed region of SUSY spectrum at the Large Hadron Collider

Date: 2017-08-08
Speaker: Dr. Abhaya Kumar Swain (PRL)
Venue: Room No. 469

Abstract

Searching for the top squark is very important in the context of stabilizing the Higgs boson mass against large quantum correction and gauge coupling unification. While Large Hadron Collider has already excluded large parameter space in supersymmetry, it poorly constrains the light top squark if the mass difference between the top squark and the neutralino is very small. Existing search strategy breaks down here mainly due to two reasons first, huge SM background and the second is unique compressed kinematics which makes all the decay products extremely soft. Here we propose a class of novel kinematic variables designed uniquely for the compressed region to control the huge SM background giving complimentary scheme in leptonic searches. We have considered the top squark undergoing four body decay in the leptonic channel and using this topology information our new kinematic variables significantly improve the current LHC limit.

Role of ENSO on spatio-temporal variation of rainfall and its delta-18-O over Indian subcontinent using GPCP and isoGSM model

Date: 2017-08-08
Speaker: Mr. P. Kiran Kumar
Venue: Ground Floor Lecture Hall

Abstract

The Indian Summer Monsoon (ISM) plays an important role in the climate of the southeast Asia. Central Indian plains receive ~80% of the annual rainfall during the summer monsoon. The rainfall over India is affected by many ocean-atmospheric coupled processes which lead to phenomenon like El-Nino Southern Oscillation (ENSO), Indian Ocean Dipole (IOD) and Madden Julian Oscillation (MJO) which occur at inter-annual to intra-seasonal time scales. These coupled processes control the strength of the monsoon and the climate of the Indian subcontinent. In this seminar, I will discuss the spatial patterns of ISM in response to ENSO at monthly to seasonal time scales. A comparison of rainfall with paleoclimate data and its implications will be presented.

Single Spins in Diamond - Precision Metrology at the Nanoscale

Date: 2017-08-04
Speaker: Dr. Gopalakrishnan Balasubramanian
Venue: G F Lecture Hall

Abstract

Leptogenesis in R violating MSSM with one $L$ violating coupling and Majorana phase

Date: 2017-08-03
Speaker: Dr. Rathin Adhikari (CTP, University of Delhi)
Venue: Room No. 469

Abstract

We have shown a new scenario of successful leptogenesis with one L violating coupling and a relative Majorana phase playing the role of CP violation. This is in contrast to the usual consideration of diagrams with at least two L violating couplings. We have considered R-parity violating Minimal Supersymmetric Standard Model (MSSM) for leptogenesis at the TeV scale. This scenario is also consistent with generating appropriate light neutrino masses with the same L violating coupling.

Impact of the range of the interaction on the quantum dynamics of a bosonic Josephson junction.

Date: 2017-08-01
Speaker: Dr. Sudip Kumar Haldar (Kolkata West Bengal)
Venue: Room No. 469

Abstract

The out-of-equilibrium quantum dynamics of a bosonic Josephson junction (BJJ) with long-range interaction is studied in real space by solving the time-dependent many-body Schrödinger equation numerically accurately using the multiconfigurational time-dependent Hartree for bosons method. Having the many-boson wave-function at hand we can examine the impact of the range of the interaction on well-known features of the BJJ dynamics at both the mean-field and many-body level. We concentrate on the tunnelling frequency, survival probability, depletion and fragmentation, and position variance of the junction, and find competitive effect between the interaction and the confining trap. The presence of the tail part of the interaction basically enhances the effective repulsion as the range of the interaction is increased starting from a small value. But as the range becomes comparable with the trap size, the system approaches a situation where all the atoms feel a constant field and the impact of the tail on the dynamics diminishes. There is an optimal range of the interaction in which physical quantities in the junction are attaining their extreme values.

The study of different extrapolation techniques

Date: 2017-07-28
Speaker: Ms Sushree Sangeeta Nayak
Venue: USO Seminar Hall

Abstract

The topological changes in the magnetic field are believed to be the driver of eruptive phenomena like flares and coronal mass ejections occurring in the solar corona. Currently, only the measurements of the photospheric vector magnetic field are available with high cadence and high resolution through various space- and ground-based telescopes. The coronal field is typically inferred by assuming an equation of state for the magnetic field such as the: potential field, linear force-free field (LFFF), non-linear force-free field (NLFFF) and non-force-free field (NFFF). In order to check the viability of these fields in describing the coronal dynamics, we extrapolate the photospheric vector magnetic field for the active region 11158 on 14th February 2011, using all the four above mentioned extrapolation techniques and compare their respective field topologies. Interestingly, these fields can also be utilized as suitable initial magnetic fields to explore the magneto hydrodynamic evolution of the active region.

Mechanical design and realisation of Chandrayaan 2 Payloads

Date: 2017-07-28
Speaker: Mr. Hiteshkumar Lavjibhai Adalja
Venue: Room - 113/114, Thaltej Campus

Abstract

Solar X-ray Monitor (XSM) on-board Orbiter to provide the real time solar X-ray flux incident on the lunar surface and Alpha Particle X-ray Spectrometer (APXS) on-board Orbiter to measure the elemental composition of lunar soil and rocks near the landing site are being developed at PRL for upcoming CHANDRAYAAN-2 mission. In this presentation I will discuss mechanical design and development activities of these two payloads.

"Nuclear structure for dark matter detection"

Date: 2017-07-27
Speaker: Dr. R. Sahu (NIST Berhampur)
Venue: Room No. 469

Abstract

There are overwhelming evidences for the existence of dark matter in the universe. However,it has not yet been observed in earth-bound experiments nor created at particle colliders.Up to now, the nature of this matter remains a mystery. The event detection rates for the WIMP (a dark matter candidate) are calculated with 73Ge as the detector. The calculations are performed within the deformed shell model (DSM) based on Hartree-Fock states. First the energy levels and magnetic moment for the ground state and two low lying positive parity states for this nucleus are calculated and compared with experiment. The agreement is quite satisfactory. Then the nuclear wave functions are used to investigate the elastic and inelastic scattering of WIMP from 73Ge. The nuclear structure factors which are independent of supersymmetric model are also calculated as a function of WIMP mass. The event rates are calculated for a given set of SUSY parameters. The calculation shows that 73Ge is a good detector for detecting dark matter.

Femtosecond and Nanosecond Laser Induced Breakdown spectroscopic and Raman studies of Nitroazoles

Date: 2017-07-26
Speaker: Dr. E. Nageswara Rao
Venue: GF Lecture Hall

Abstract

Nanosecondand Femtosecond Laser Induced Breakdown Spectroscopy (LIBS) spectra/data of a series of Nitrates, Pyrazoles and Imidazoles were recorded in air, argon and nitrogen atmospheres to understand the formation of molecular species of CN and C2. Molecular species formation was dominant with fs excitation (versus atomic species dominance in the ns LIBS data).The LIBS spectra were analysed for understanding (a) the influence of molecular structure i.e. type of bonds (C-C, C=C, C-N and C=N) on atomic (C, H, N and O) and molecular (CN, C2 and NH) emissions, (b) effect of surrounding atmosphere on the fs and ns LIBS spectra, (c) correlation between stoichiometric and intensity ratios of molecular as well as atomic species, (d) effect of the number of substituents and their position in the ring on the fragmentation pathways and (e) correlation between oxygen balance and LIBS spectra. Such data will be helpful for discrimination of explosive molecules from non-explosives. Time resolved spectral analysis were performed on molecular (CN, C2) and atomic (C, H, N and O) emissions to understand the plasma dynamics, and alsodetermined the decay times in three atmospheres. Plasma temperature and electron density were measured for Cu I, Li I and Ba I plasma of nitrates with nanosecond (ns) excitation in air atmosphere.IR and Raman spectra of these molecules were also studied both experimentally and theoretically.

Dissecting Multi Photon Resonances at the Large Hadron Collider

Date: 2017-07-25
Speaker: Dr. Abhishek Iyer (TIFR Mumbai)
Venue: Room No. 469

Abstract

We examine the phenomenology of the production, at the 13 TeV Large Hadron Collider (LHC), of the production of a heavy resonance $X$, which decays via other new on-shell particles $n$ into multi- (i.e.\ three or more) photon final states.In the limit that $n$ is light compared to $X$, the multi-photon final state may dominantly appear as a two photon final state because the $\gamma$s from the $n$ decay are highly collinear and are not resolved. We discuss how to discriminate this scenario from $X \rightarrow \gamma \gamma$: rather than discarding nonisolated photons, it is better to relax the isolation criterion and instead form photon jet substructure variables. The spins of $X$ and $n$ leave their imprint upon the distribution of pseudorapidity gap $\Delta \eta$ between the apparent two photon states. Depending on the total integrated luminosity, this can be used in many cases to claim discrimination, although the case where $X$ and $n$ are both scalar particles cannot be discriminated from the direct $X \rightarrow \gamma \gamma$ decay in this manner. In addition, one can bound the mass of $n$ by the mass of each photon jet.

Corals from Indian Ocean - proxy for Indian Monsoon

Date: 2017-07-25
Speaker: Mr.Harsh Raj
Venue: Ground Floor Lecture Hall

Abstract

Indian monsoon is an integral part of climate over Indian subcontinent and has influence on large part of Indian population. Therefore, understanding past changes in strength of Indian monsoon is important. Winds associated with monsoon causes changes in sea surface condition which is recorded by corals. d18O, d13C and delta14C values of coral carbonate skeleton can be used as proxy for past sea surface conditions and can be studied to understand past change in strength of Indian monsoon. Corals from the northern Indian Ocean record sea surface temerature (SST) variations induced by upwelling due to monsoon winds. These SST changes also affects the growth rate of the corals. Some preliminary observations on coral growth rate from Lakshadweep will be discussed

Generation of vector vortex beam from doubly resonating optical parametric oscillators

Date: 2017-07-21
Speaker: Mr. Varun Sharma
Venue: GF Lecture Hall

Abstract

Polarization of light is a consequence of the vectorial nature of electromagnetic field and it can be represented as a spin angular momentum of light. Beside that, light beam also carry orbital angular momentum. For most of the analysis, light beam is considered as scalar in nature in which polarization is same all across the beam. But one can couple these two momentum states of light to generate vector vortex beams. Here, we generate such vector vortex beam using optical parametric oscillators (OPO), where we can exploit all the advantages of OPO to generate highly stable, tunable vector vortex beam. Further discussion on generation techniques and application will be presented in the seminar.

Viscous dark matter growth in (neo-) Newtonian cosmology

Date: 2017-07-20
Speaker: Mr. Arvind Kumar Mishra (PRL)
Venue: Room No. 469

Abstract

The cosmic structure formation on the subhorizon scale can be studied within the Newtonian framework of pressureless cold dark matter (CDM). However, if there is small but nonzero pressure of CDM then the Newtonian description will not be valid. In this talk we will argue that a new Newtonian approach will resolve the problem of Newtonian approach by incorporating pressure effects into the cosmic fluid dynamics and reproduces the general relativistic dynamics as well. Assuming that the CDM have small bulk viscosity, we will discuss about the effects of viscosity on the growth of scalar perturbations and put upper limit on the viscous coefficient.

Microbial life: At interface and in the aqueous marine environment

Date: 2017-07-18
Speaker: Dr. Anand Jain
Venue: Ground Floor Lecture Hall

Abstract

Microbes in any bulk phase (liquid or gas) tend to accumulate or attach at interfaces, such as solid-liquid, liquid-gas and solid-gas. The microbial life at interfaces is often termed as biofilms. Biofilm formation is usually detrimental to human health and man-made structures including ships, underwater pipelines, submersibles etc. On the other side, they are beneficial for the degradation of waste, organic carbon and production of value added products. During this presentation we will discuss the mechanisms underlying bacterial adhesion and biofilm formation onto to solid surfaces, as well as electron transfer mechanism in microbial biofilms capable of generating electricity via organic matter oxidation. Microbes in the ocean play an important role in biogeochemical cycling of carbon, nitrogen, phosphorus, iron and sulfur. They form the base of marine food chain, recycling nutrients and organic matter, and producing vitamins and cofactors needed by higher organisms to grow and survive. Understanding of microbial community structure and function is very crucial for elucidating their role in various biogeochemical cycles and impact on or of climate change. The factors influencing bacterial community structure in marine environment and role of marine bacteria in carbon cycling will be discussed.

Rare B decays as a probe of New Physics

Date: 2017-07-17
Speaker: Ms. Bharti Kindra (PRL)
Venue: Room No. 469

Abstract

Rare B decays have been used as testing grounds for the Standard Model.LHCb and Belle have measured optimized observables for B decaying to (K,K*)ll and reported several anomalies. Theoretical predictions for these observables are made using non-perturbative QCD calculations which are often plagued with large uncertainties.One can associate the observed anomalies either to these uncertainties, or some New Physics. In this talk we give predictions for these observables for other rare B decay modes which can be used to confirm the presence of New Physics.

Synoptic features of fine and coarse mode aerosols over an urban region

Date: 2017-07-17
Speaker: Atar Singh Pipal
Venue: Ground Floor Lecture Hall

Abstract

Aerosols are an important component of the Earth's atmosphere which plays a significant role in influencing the air quality and climate on regional and global scales. Aerosols influence directly the Earth-atmosphere radiation budget by scattering and absorbing incoming solar and outgoing long wave radiation. In the seminar I will discuss the results obtained from a year-long measurement of aerosol size distribution (0.253-9.575 µm radius) on diurnal, monthly and seasonal basis, and their fine and coarse fractions over Ahmedabad. Details of measurement techniques and data analysis will be presented in the talk. The results obtained will be compared with those obtained at other urban locations and inferences will be drawn.

SIMP: An alternate dark matter candidate

Date: 2017-07-13
Speaker: Mr. Ashish Narang (PRL)
Venue: Room No. 469

Abstract

A Weakly Interacting Massive Particle (WIMP) has been the preferred Dark Matter (DM) candidate. But the tightening of the constraints on the standard thermal WIMP scenario has forced physicists to propose alternative scenarios of DM. One such alternate scenario is the strongly interacting massive particle (SIMP) mechanism of dark matter freeze out. In this talk I will discuss one such DM model in which, under the assumption that DM annihilation into SM particles is suppressed, the SIMP mechanism dominates the freeze out of DM. I will show that a DM of MeV order mass with sufficiently strong self interaction gives the correct relic density of dark matter.

Sensing the space rocks – the optical spectrum of asteroids

Date: 2017-07-13
Speaker: Mr. Kumar Venkataramani, PRL, Ahmedabad
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The asteroids revolving around the Sun today may have been a part of some major planetary body, a failed planet or just broken bits of rock ever since their formation in the proto-planetary disk. Today, the major chunk of these space rocks are found clustered around at different locations in the solar system, gravitationally bound by the major planets. The reflectance spectra and the geometric albedo of these asteroids depend on their surface composition, the macroscopic roughness of surface, opposition surge brightness at low phase angles and the overall shape of the asteroid. Based on their reflectance slopes, albedos and absorption bands, these asteroids have been put into various taxonomic classes and sub-classes. Near-Earth flyby's of some of these asteroids give us good opportunity to study them with a large phase angle coverage. Two such Near-Earth flyby's were spectroscopically followed with the optical low resolution spectrograph LISA mounted on the 0.5m and 1.2m telescopes at the Mount Abu Infra-red Observatory(MIRO). One of them being the recent close shave of the potentially hazardous asteroid 2014JO25 in April 2017. Time and phase resolved spectra of this asteroid gave very interesting clues on its uniqueness. Apart from this, we have also spectroscopically followed many of the main-belt asteroids of different taxonomic classes at different times. This talk will give a brief overview of the different classes of asteroids and some of the key results from their optical spectra.

Photospheric changes leading to solar eruptions

Date: 2017-07-13
Speaker: Mr. Ranadeep Sarkar
Venue: USO Seminar Hall

Abstract

Understanding the enigma of accretion powered X-ray binary pulsars

Date: 2017-07-12
Speaker: Dr. Gaurava Jaiswal, PRL, Ahmedabad
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Be/X-ray binaries are among the brightest transient sources in the Galaxy. They mostly harbor neutron star as a compact object, revolving in a wide eccentric orbit around massive Be spectral type optical companion. These sources show periodic or Type-I X-ray outbursts, usually associated with periastron passage of binary. It is believed that neutron star accretes matter from a circumstellar disk bound to the Be star and powers such strong outbursts. We have studied Be/X-ray binary pulsars such as Cep X-4, GX 304-1 and SMC X-2 during Type-I X-ray outbursts for understanding the characteristics of emission geometry, accretion physics, evolution of spectral continuum, cyclotron lines, and magnetic field mapping around these exotic objects, by mainly focusing on timing and spectral aspects using Suzaku and NuSTAR observations. The results obtained from these studies and some other accretion powered X-ray pulsars will be discussed in this talk.

Effect of Long Range Force on Neutrino Oscillations

Date: 2017-07-11
Speaker: Mr. Kaustav Chakraborty (PRL)
Venue: Room No. 469

Abstract

Neutrino oscillation physics has been well studied under the framework of interactions governed by the Standard Model gauge group. But this gauge group can be extended to include an extra anomaly free U(1) symmetry Le − Lµ , Le − Lτ or Lµ − Lτ . Hence, the new gauge group becomes SU(3)C ⊗SU(2)L ⊗U(1)Y ⊗U(1)X. Under this new gauge group an extra Z’ boson is introduced, which, if sufficiently light will provide a Long Range Force which can significantly contribute to Neutrino Oscillations. I will discuss the theoretical and phenomenological aspects of Neutrino Oscillations under the effect of this Long Range Force.

Long-term isotope record of daily precipitation at Ahmedabad in semi-arid western India: insights into regional hydrometeorological processes.

Date: 2017-07-11
Speaker: Mr. Harsh Oza
Venue: Ground Floor Lecture Hall

Abstract

There are numerous published studies, which confirm that the weather systems across the globe are undergoing changes, as manifested in trends in temperature, rainfall, heat waves, cyclones, floods and droughts on decadal or sub-decadal scales. In spite of the recognition of various broad patterns in weather indices, there is lack of clarity about the changes in the subtle hydro-meteorological processes in different climatic regions. Many of the meteorological phenomena are so localised that concept of a few homogenous meteorological regions across the India is no more convincing. It this scenario, it is important to understand the contemporary hydro-meteorological processes from several locations, which determine the spatio-temporal distribution of water in atmosphere, surface and sub-surface domains. It is the only option, until major climate change is recognized after a few decades of systematic changes in weather and its severe consequences on socio-economy. >From this perspective, Ahmedabad city (23.03°N; 72.55°E) in the hot semi-arid western India is an important geographic location to investigate the hydrometer logical processes because it has been experiencing erratic weather extremes such as heat waves, cloud bursts, floods and droughts, superposed on the climate normal. Stable isotopes of oxygen and hydrogen in precipitation can provide information about the source of vapour, rainout history, vapour recycling, post-precipitation modifications, cloud micro-physical processes etc. Considering this, stable isotopes of oxygen and hydrogen have been monitored in daily precipitation at Ahmedabad since last 12 years(2005-2016). A rigorous analyses of this important isotope dataset in conjunction with other ground based and remotely sensed meteorological parameters will be presented in this seminar.

Flavour structure from SO(10) X U(1) gauge theory in 6D

Date: 2017-07-07
Speaker: Dr. Ketan Patel (IISER Mohali)
Venue: Room No. 469

Abstract

I will briefly discuss an origin of quark-lepton multiplicities from the flux of an anomalous U(1) with SO(10) gauge theory in six dimensions. I will then describe how a realistic flavor phenomenology can be obtained in the framework.

Effect of non-standard neutrino interactions on the sensitivities of DUNE

Date: 2017-07-06
Speaker: Dr. K Naga Deepthi (PRL)
Venue: Room No. 469

Abstract

Deep Underground Neutrino Experiment (DUNE) is a potential long-baseline neutrino oscillation experiment of the next generation. It can act as a promising probe to new physics scenarios like non-standard neutrino interactions (NSI), which is a subleading phenomenon to the well established neutrino oscillations.In this work, we consider the effect of non-standard interactions (NSIs) on the propagation of neutrinos through matter and how they in turn affect the sensitivity of the DUNE in determining the mass hierarchy. We emphasize on the special case - when the diagonal NSI parameter ee = −1 at which the standard matter effect gets nullified. We show that, if in addition, there is maximal CP violation then this gives rise to an exact intrinsic hierarchy degeneracy, in the appearance channel, irrespective of the baseline and energy. Considering current model independent bounds on NSI parameters we observe that the hierarchy sensitivity of DUNE gets seriously compromised if NSI exists in nature. A signal of neutrino mass hierarchy at DUNE will therefore be able to rule out certain ranges of the NSI parameters. Additionally, we discuss the implications of ee = −1 (in the Earth) on MSW effect in the Sun.

Modelling the physical and biogeochemical interactions of the north Indian Ocean

Date: 2017-07-04
Speaker: Dr. Abhisek Chatterjee
Venue: Ground Floor Lecture Hall

Abstract

The Indian subcontinent divides the north Indian Ocean (IO) into two smaller basins, Arabian Sea (AS) in the west and Bay of Bengal (BoB) in the east. Owing to the close proximity of the equatorial IO, the circulation in the BoB and AS is not only driven by the local winds, but also largely influenced by forcing from the equatorial Indian Ocean. In this talk, I will discuss various equatorial processes that primarily drive the circulation in the bay and East India Coastal current (EICC) in particular. I will also show results from a biogeochemical model based on Modular Ocean Model (MOM) to explain some of the key bio-physical interactions in the north Indian Ocean.

A Song Of Ice And Flavor

Date: 2017-07-03
Speaker: Mr. Bhavesh Chauhan (PRL)
Venue: Room No. 469

Abstract

In the recent measurement of lepton flavor universality violation by LHCb, a 2.5 sigma deviation from the standard model prediction was observed. One of the most common explanations of these anomalies invokes leptoquarks with intergeneration Yukawa-like couplings. In this talk, I will show that the scalar doublet leptoquark with hypercharge 7/6 can accommodate these recent flavor anomalies along with the excess in the anomalous magnetic moment of the muon, and the very high energy neutrino events observed at IceCube. Within this framework, the flavor anomalies are generated at one loop level, and IceCube events are explained via resonant production of the leptoquark.

τ reconstruction to determine CP properties of the Higgs boson at the LHC

Date: 2017-06-27
Speaker: Ms. Akanksha Bhardwaj (PRL)
Venue: Room No. 469

Abstract

In our ongoing endeavor to uncover properties of the Higgs boson at the LHC, looking for event where the Higgs boson decays into third generation τ ’s is the natural first step in exploring the interactions of the Higgs boson with leptons. We propose a technique to reconstruct the full kinematics at the LHC to pin down the CP properties in the corresponding Yukawa coupling. The reconstruction technique works well for 1- prong decays as well as 3- prong decays. Hence several CP sensitive observable corresponding to different τ decay modes can be studied.

Understanding Aluminium Biogeochemical Cycle in the Indian Ocean

Date: 2017-06-27
Speaker: Mr. Naman Deep Singh
Venue: Ground Floor Lecture Hall

Abstract

Deposition of mineral dust over oceans and their subsequent partial dissolution in seawater is an important mechanism for supply of bio-essential trace metals to the open oceans. Due to dearth of direct estimates of dust deposition fluxes over oceans (especially in most remote regions such as Southern Oceans), development of proxy to dust supply over global oceans is imperative. Dissolved aluminium (dAl) in the surface waters of remote oceans: 1) is majorly brought through eolian input, 2) has short residence time (few weeks to ~4 years) and 3) is not bio-limiting and redox insensitive. Therefore, dAl distribution in the surface waters of open oceans has been historically and recently used to model the dust deposition fluxes over oceans. However, dAl data in the world oceans is sparse with Indian Ocean among the most under sampled region. Also, dAl concentrations have shown large inter-basin fractionation due to the varying sources (eolian, sedimentary, etc.) and oceanic processes, such as water mass advection, differential scavenging, etc. Evidences of incorporation of Al from the water column to biogenic opal are also present and hence Al coupling with the Si-cycle in seawater is suspected. Together, all the above mentioned processes, suggest for the comprehensive evaluation of biogeochemical cycling of Al in seawater for more refine assessment of dAl derived dust deposition fluxes. In this talk, I shall discuss different processes, source and sinks of dAl to the oceans which govern its distribution. Also, recently established fluorimetric method for the detection of nanomolar levels of dAl in seawater and preliminary results achieved from northern Indian Ocean will be presented.

Timing and spectral properties of accretion powered X-ray pulsars

Date: 2017-06-27
Speaker: Ms. Shivangi Gupta, PRL, Ahmedabad
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Accreting X-ray pulsars are the brightest objects in the X-ray sky. They are usually found in an X-ray binary system in which a neutron star accretes matter from an optical companion via Roche robe overflow or through the strong stellar winds emanating from its companion. During the accretion process, the matter from donor interacts with the pulsar’s strong magnetic field and forced to follow the field lines to magnetized poles of the neutron star. This results in the formation of a column like structure on the top of the neutron star, which acts as the main source of pulsating X-ray emissions. The basic structure of the emitting region, accretion physics, and tool to probe the magnetic field can be studied by understanding the timing and spectral properties of pulsars. In this talk, I will discuss the properties of such interesting sources along with a curious case study of X-ray binary pulsar GX 1+4.

Z_N symmetry and Confinement-Deconfinement transition in SU(N)+Higgs theory

Date: 2017-06-22
Speaker: Dr. Minati Biswal (Institute of Mathematical Sciences, Chennai)
Venue: Room No. 469

Abstract

At very high temperatures, around ~150MeV, hadrons melt to form the QuarkGluon Plasma (QGP). Such extreme thermal conditions existed in the early Universe and currently are being created in heavy-ion collision experiments. Theoretical studies using Quantum ChromoDynamics (QCD) show that the melting of hadrons to QGP proceeds via the confinement-deconfinement (CD) transition. Interestingly this transition occurs in all SU(N) gauge theories like QCD. The nature of this transition depends greatly on the presence of matter fields. This has to do with the Z_N symmetry which describes well the CD transition when the matter fields are not considered. It is spontaneously broken in the deconfinement phase and gets restored in the confinement phase. The presence of matter fields is supposed to break this symmetry explicitly making the CD transition weaker. We study this explicit symmetry breaking in SU(N) gauge theories by considering only the bosonic matter fields. Contrary to conventional expectations we find vanishing explicit symmetry breaking in parts of the relevant phase diagrams.

Cold Gas at High Redshift

Date: 2017-06-21
Speaker: Dr. Nissim Kanekar
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The gas and dynamical masses of damped Lyman-alpha absorbers (DLAs), a population of absorption-selected galaxies, have been open questions in the field of galaxy evolution for more than three decades. This talk will describe new results from Arecibo and ALMA searches for HI 21cm, CO and CII-158 micron searches emission from a sample of DLAs at, respectively, low (z < 0.1), intermediate (z~0.7) and high (z~4) redshifts. Our HI 21cm observations of the DLAs at z<0.1 yield normal gas masses, <~ 5 x 10^9 solar masses, but very high ratio of gas mass to stellar mass, ~ 5-100, far higher than in normal galaxies. For the absorbers at intermediate redshifts, we obtain large molecular gas masses in the six systems with CO detections, despite their low optical star formation rates. We also obtain high star formation rates (based on dust continuum emission) and high CII-158 micron line luminosities for the DLA host galaxies at z~4. For the CO and CII-158 micron detections, the impact parameters of the host galaxies are high, 15-45 kpc, far larger than expected based on earlier studies. These are the first CO and CII-158 micron detections in DLA hosts, providing a new window on physical conditions in absorption-selected galaxies, and yielding a new tool to identify DLA host galaxies at high redshifts.

Heavy quarkonia in a strong magnetic field

Date: 2017-06-20
Speaker: Mr. Balbeer Singh (PRL)
Venue: Room No. 469

Abstract

Quark-gluon plasma is the state of strongly interacting matter where quarks and gluons are deconfined and which is created in RHIC @ BNL and LHC @ CERN. In heavy ion collisions, a very strong magnetic field is also created in the noncentral collision of ions which is strong in the initial state of the collision and rapidly decreases with time. The presence of this magnetic field affects the QCD plasma screening which leads to observable changes in QGP properties. One of these is the heavy quarkonia potential and dissociation of quarkonia. In this seminar, I will discuss how the quarkonium potential gets modified in a magnetized quark-gluon plasma. I will also discuss the Debye screening in the lowest Landau level approximation and the quarkonium decay width in the strong field limit.

Collective modes of a hot anisotropic QCD medium with Bhatnagar-Gross-Krook collision term

Date: 2017-06-13
Speaker: Dr. Avdhesh Kumar (PRL)
Venue: Room No. 469

Abstract

In the heavy ion collision experiments the initial geometry of the hot QCD matter created is approximately almond shaped with only spatial anisotropy. Due to the expansion, the different pressure gradients in different directions cause a momentum anisotropy to develop which is present throughout the hydrodynamical expansion of the hot QCD matter. Therefore, it is inevitable to include such anisotropic effects while modeling a hot QCD medium. Collisions among the hard particles are responsible for the dissipation and needed for the hot QCD matter to reach the stage of equilibrium. Therefore, one simply can not ignore the collisions. Collective modes/excitation of hot QCD plasma can be understood as the collective motion that the plasma possesses due to the fluctuations in the equilibrium stage. The modes carry crucial information about the equilibrated QGP and play an important part in its dynamical evolution. The spectrum of the collective modes of the QGP can be studied with the help of the self-energy of the medium. In the seminar I shall discuss how the gluon self-energy of a hot anisotropic QCD medium (when medium interactions are also present) can be obtained using the semi-classical transport equation with Bhatnagar-Gross-Krook (BGK) collision term. I shall also discuss how the tensor decomposition of the gluon self energy leads to the structure functions which eventually control the dispersion relations and the collective mode structure of the medium.

Impact of the Oxygen minimum zone (OMZ) on marine Zinc cycle: Results from the GEOTRACES GI-10 cruise

Date: 2017-06-13
Speaker: Mr. Venkatesh Chinni
Venue: Ground Floor Lecture Hall

Abstract

Zinc (Zn) is considered as a key trace element for primary production in seawater along with the Iron. Zinc showed a nutrient type behaviour with lower concentration in the surface waters than underlying waters. A strong and significant correlation is observed between Silicate (Si) and Zn in the GI-10 section. However, a lower slope is observed between Zn vs. Si in the Northern Indian Ocean compared with the global data. In addition to this, decoupling of Zinc and Silicate has been observed in the OMZ waters of the Northern Indian Ocean. Results are suggesting that water column oxygen depletion has a substantial impact on Zn biogeochemical cycling, impacting the global relationship between Zn and major nutrients. In this talk, I will discuss about the Zn distributions and its internal cycling in the Northern Indian Ocean.

Black Hole Horizon as a Fluid and the Outlines of a Transport Theory

Date: 2017-06-12
Speaker: Dr. Swastik Bhattacharya (IISER Thiruvananthapuram)
Venue: Room No. 469

Abstract

It has been known for a long time that the horizon of a black hole behaves like a viscous fluid. This is very suggestive in view of the fact that black holes possess a large entropy. Here we show how to construct a transport theory for the horizon-fluid with the final aim of developing a microscopic theory for this fluid. We shall determine the coefficient of bulk viscosity for the horizon-fluid and show that it indicates that the fluid system has a mass gap. Then we shall also briefly discuss the shear viscosity and the electrical conductivity of this fluid. Finally, based on the evidence gathered so far, I shall suggest what kind of field theory might be expected to underly the macroscopic picture of the horizon-fluid.

Spectral and transport responses of quark and hadronic matter

Date: 2017-06-08
Speaker: Dr. Sabyasachi Ghosh (University Of Calcuttta)
Venue: Room No. 469

Abstract

It is believed that up to a few microseconds after the Big Bang, the universe was in a state of quark matter followed by hadronic matter, with temperatures much larger than the temperature of the Sun. The experiments of heavy ion collisions like RHIC at BNL, USA and LHC at CERN, Switzerland have successfully produced this kind of an artificial baby universe, having a temperature of the order of a trillion degrees Kelvin, which is considered as the highest man-made temperature till now. Our studies focus on this early universe state by investigating its in-medium spectral and transport responses, where quantum field theory at finite temperature is used as the main mathematical tool. The investigation on spectral responses is aimed at explaining the so called “low mass dilepton enhancement”, as a signature of the medium, whereas the studies of transport responses have tried to probe the (nearly) perfect fluid nature of such a medium.

Nitrogen- Inside and out of the soils

Date: 2017-06-06
Speaker: Ms. Niharika Sharma
Venue: Ground Floor Lecture Hall

Abstract

Nitrogen is a fundamental element required to sustain all life forms. Although there is plenty of nitrogen available in the atmosphere, basic of the hierarchy- the primary productivity which also behaves as the largest natural sink of atmospheric carbon dioxide, is limited by the availability of active forms of nitrogen. Where nitrogen in form of ammonium and nitrate behaves as a nutrient required by primary producers, in another form (nitrous oxide) can act as a potent greenhouse gas. Recent studies shows that the behavior of nitrogen transformations can largely be affected by the anthropogenic activities and climate change. During my talk, I would discuss about the importance of various forms of nitrogen and their dynamics in the terrestrial ecosystems and its status in India.

Astrophysical coronae: from sun to galaxy clusters

Date: 2017-06-06
Speaker: Dr. Prateek Sharma
Venue: USO Seminar Hall

Abstract

Review of Cosmological Perturbation Theory

Date: 2017-06-01
Speaker: Ms. Richa Arya (PRL)
Venue: Room No. 469

Abstract

Observations of the Cosmic Microwave Background (CMB) radiation indicate anisotropies in the temperature to be 1 part in 105 in a nearly uniform thermal radiation of 2.725 K. The presence of these anisotropies can be attributed to the primordial energy density fluctuations generated in the early Universe. In this talk I will discuss the mathematical tools and construction of Cosmological Perturbation Theory used to study these anisotropies. I will also discuss how the seed fluctuations generated in the early Universe evolve into the features in the angular power spectrum observed in the CMB today.

Organic Aerosol: Composition and Chemistry

Date: 2017-05-30
Speaker: Dr. Neeraj Rastogi
Venue: Ground Floor Lecture Hall

Abstract

Impact of Corotating Interaction region (CIR) and Coronal mass ejection (CME) on magnetosphere-ionosphere system

Date: 2017-05-29
Speaker: Diptiranjan Rout
Venue: Ground Floor Lecture Hall

Abstract

The CME and CIR are two primary drivers of space weather. The consequences of these space weather events are severe in a modern day society. Therefore, it always remains a challenging topic in the space weather community to predict and understand the geo-effectiveness of these events. In one of our recent study, it is shown that the CIR events can be geo-effective in terms of their ionospheric impact if the solar wind azimuthal flow angle does not exceed a critical angle (6 degree) at first Lagrangian (L1) point. Thus, this result provides an easy and quick method to forecast the geo-effectiveness of CIR events based on the observations from the L1 point. Based on another investigation, it is also shown that the global magnetosphere-ionosphere system can be significantly influenced by the passage of an ICME driven sheath region even in absence of a typical geomagnetic storm as inferred using Dst variation. These results unravel a few critical aspects of the impact of the space weather events on magnetosphere-ionosphere coupling processes.

Direct transfer of pump amplitude to parametric down-converted photons

Date: 2017-05-26
Speaker: Ali Anwar
Venue: GF Lecture Hall

Abstract

Spontaneous parametric down-conversion (SPDC) is a well-known process used to generate twin photons that are correlated in various degrees of freedom. The spatial correlation between the photon pairs guarantees that the angular spectrum of the pump is transferred to the SPDC 'heralded' single photon. Due to the incoherence of individual parametric down-converted photons, the angular spectrum of SPDC does not evidently show the signature of spatial properties of the pump. Here, we theoretically and experimentally show that the amplitude distribution of the pump beam is revealed in the Fourier plane of SPDC distribution restricted by an aperture. Phase measurements show that the SPDC mode distribution does not contain the transverse phase corresponding to that of the pump mode. The results might be useful for applications of SPDC in quantum imaging and quantum information.

Effects of the trace anomaly on the Stochastic Gravitational Wave background

Date: 2017-05-25
Speaker: Mr. Sampurnanand
Venue: Room No. 469

Abstract

One of the important sources of the stochastic Gravitational Wave Background (SGW) is cosmological phase transitions. Apart from the dynamics of the phase transition, the characteristic frequency and the fractional energy density of the SGW depends upon the temperature of the transition. We compute the SGW spectrum in the light of QCD the equation of state provided by lattice results. We find that the inclusion of trace the anomaly enhances the SGW signal generated during the QCD phase transition by ~50% and the peak frequency of the QCD era SGW are shifted higher by ~25% as compared to the earlier estimates without trace anomaly. This result is extremely significant for testing the phase transition dynamics near the QCD epoch.

Evidence of solar forcing on late Quaternary paleo-monsoonal records from the equatorial Indian Ocean

Date: 2017-05-23
Speaker: Ms. Chandana K.R.
Venue: Ground Floor Lecture Hall

Abstract

The late quaternary period witnessed drastic climate perturbations in the form of glacial-interglacial cycles as results of solar forcing. Migration of the Intertropical Convergence Zone (ITCZ) is significantly influenced by solar variability thereby causing seasonal reversal of monsoonal winds over India and adjacent regions. Based on geochemical and isotopic proxies, changing monsoonal intensity and its influence on overhead productivity during late quaternary period from the intermixing zone of the Bay of Bengal and the Arabian Sea would be discussed. The study demonstrates the solar forcing of various processes as deciphered from solar periodicities in the sediment records of the equatorial Indian ocean.

Evolution of the Mesoproterozoic Chattisgarh basin: A geochemical perspective

Date: 2017-05-16
Speaker: Mr. Bivin Geo George
Venue: Ground Floor Lecture Hall

Abstract

The Mesoproterozoic Era (1.6 - 1.0 Ga) in the Earth’s history is characterized by environmental, evolutionary, and lithospheric stability that contrasts the dramatic changes happened in the preceding and succeeding eras. In the talk, I shall discuss our on-going efforts in understanding the Mesoproterozoic records of India through geochemical studies of the sediments deposited in the Chattisgarh basin. Results of our study aimed at constraining the age, understanding the provenance, paleogeography and tectonic setting of the basin shall be presented in the talk.

Common Origin of Neutrino Mass, Dark Matter and Dirac Leptogenesis

Date: 2017-05-11
Speaker: Dr. Arnab Dasgupta
Venue: Room No. 469

Abstract

We study the possibility of generating tiny Dirac neutrino masses at one loop level through the scotogenic mechanism such that one of the particles going inside the loop can be a stable cold dark matter (DM) candidate. Majorana mass terms of singlet fermions as well as tree level Dirac neutrino masses are prevented by incorporating the presence of additional discrete symmetries in a minimal fashion, which also guarantee the stability of the dark matter candidate. Due to the absence of total lepton number violation, the observed baryon asymmetry of the Universe is generated through the mechanism of Dirac leptogenesis (neutrinogenesis).

The magic of flares in Gamma-ray bright blazars

Date: 2017-05-11
Speaker: Ms. Navpreet Kaur
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The advancement of Gamma-ray detection techniques (since the launch of Fermi in 2008-post CGRO) has helped our understanding of one of the most powerful Cosmic accelerators in the Universe, called blazars. Blazars prove to be one of the promising candidates in exploring the enigmatic nature of AGN, during their flaring (or outburst) in gamma-rays and all the way down to radio frequencies. Since their emission is detectable across the whole spectrum, their variability properties across all timescales, from years to few minutes, shed light on their emission processes inside the jet. Flaring phases in these sources are helpful in understanding their acceleration/cooling mechanisms and their connection across all other frequencies. In this talk, I will discuss about flaring patterns in gamma-ray bright blazars, their role in the understanding till date with a few examples from our study.

Biogeochemical investigation on eastern Indian estuaries

Date: 2017-05-09
Speaker: Dr. Manab Kumar Dutta
Venue: Ground Floor Lecture Hall

Abstract

A comprehensive investigation was conducted at Hooghly estuary and major estuaries of Indian Sundarbans (Saptamukhi, Thakuran and Matla) during summer-time, 2016. The estuaries of Sundarbans were mainly marine dominated (polyhaline) while a sharp salinity gradient was noticed for the Hooghly estuary. At this study, stable isotopes have been widely used for the first-time to understand hydrological as well as biogeochemical processes (mainly carbon) operating within these two contrasting estuarine systems (anthropogenic vs. mangrove dominated estuaries). Variability of δ18O and δD within the given sampling stretch clearly indicates proper mixing of fresh and marine water at Hooghly estuary while the case was not so effective for the estuaries of Sundarbans. Moreover, during summertime impact of these estuarine systems on regional climate will be also discussed based on computed emission of radiatively active trace gases (CO2 and CH4) from water - atmosphere interface.

Comparison of quiet time vertical plasma drifts with global empirical models over the Indian sector: Some insights

Date: 2017-05-08
Speaker: Kuldeep Pandey
Venue: Ground Floor Lecture Hall

Abstract

Using the equatorial electrojet model developed in PRL and magnetometer measurements over India, a methodology is evolved to obtain the ionospheric electric fields and vertical plasma drifts during daytime that are otherwise difficult to obtain systematically in the absence of incoherent scatter radar. Vertical drifts derived by this methodology and other past measurements over the Indian sector are compared with the global empirical model values. This exercise provided valuable insights into the low latitude ionospheric processes. These results will be presented and discussed in this presentation.

Molecular Anions in Intense Laser Fields: Competing Electronic and Nuclear Motion Dynamics

Date: 2017-05-05
Speaker: Dr. Abhishek Shahi
Venue: Room No: 006, Thaltej Campus

Abstract

The study of ultrafast intense laser interaction with neutral atomic systems revealed ground breaking phenomena such as non-sequential double ionization and high order harmonic generation of attosecond pulses. Because of their different energetics and high degree of electron correlations, anionic systems are expected to present new intense field mechanisms. I will present our recent work on intense field interaction with atomic, molecular and cluster anionic systems. Using the fast beam method and cutting edge 3D coincident fragment imaging, I disentangle all the possible interaction processes. For each fragmentation process, the characteristic angular resolved kinetic energy release distributions are studied as a function of laser peak intensity as well as time resolved in two-color pump-probe experiments. Early studies revealed efficient non-sequential multiple-detachment mechanism that does not rely on re-scattering dynamics, which dominate intense field interactions with neutral species. In particular, I will demonstrate how photodissociation competes with photodetachment, double detachment and Coulomb explosion of the relatively simple F2 ̄ molecular anion. While dissociative photodetachment is dominated by sequential dissociation followed by detachment of the atomic F ̄product, double-detachment exhibits competing sequential and non-sequential contributions, while multiple detachment is non sequential in nature and results in Coulomb explosion.

Automatic Analysis Tools for Stellar Parametrization and classification of cool stars

Date: 2017-05-05
Speaker: Dr. Kaushal Sharma
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

With the ongoing/upcoming large ground and space-based surveys, such as Kepler mission, Hubble Space Telescope, AstroSat, SDSS, Gaia, JWST etc., large astronomical databases have become accessible in the real-time. But, growth in the data reduction and analysis sector does not match up well with the corresponding growth in data collection domain. However, automatic stellar parameter (Teff, logg and [Fe/H]) determination from low-resolution spectroscopy has seen some advancement in the past two decades. Automated algorithms for parameterization (or spectral classification) can be broadly put into two categories: Minimum distance methods (MDMs) and Non-linear regression methods. An example of each of these techniques, Full spectrum fitting and Artifical Neural Networking (ANN), would be discussed. Full spectrum fitting has been applied and improved for cool stars which are the most probable targets for the exoplanet studies. Moreover, these are the crucial player for galactic kinematics and chemical enrichment analysis. Therefore, their accurate parameter determination becomes of vital importance. Improved parameters of cool stars using full spectrum fitting technique will be presented.

Amplitude of solar wind density turbulence from 10 - 45 Rs

Date: 2017-05-04
Speaker: Dr. Madhusudan Ingale
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Turbulent fluctuations in the solar wind leads to wide variety of phenomena. Amplitude of solar wind density turbulence ($C_N^2$) and density modulation index ($\epsilon_N$) are two important parameters often invoked to interpret various observations as well as transport properties of the solar wind. In this work we report on C_N^2 and \epsilon_N in the solar wind between 10 and 45 R_{\odot}. We derive these quantities using general structure function, observationally constrained by the occultation observations of the crab nebula made in 2011 and 2013 and similar observations published earlier. Our work yield a comprehensive picture of, a) the manner in which C_N^2 and \epsilon_N vary with heliocentric distance in the solar wind and b) Solar cycle dependence of these quantities.

Quantum transport in the confined region of potential well and disordered wire

Date: 2017-04-28
Speaker: Dr. Surender Pratap
Venue: Room No. 469

Abstract

We report and adduced band structure in the confined region of potential well. LDOS, transmission, charge distribution have been calculated in the confined region of well. Transmission curves show oscillations with the increase of layers of unit cell. While in other part, we study level spacing distributions of finite sized 1-dimensional disordered systems. As the systems evolves from quasi ballistic to strongly localized regime, systems crosses over from strongly non-Wigner-Dyson type level spacing distribution to a universal Poisson distribution in the thermodynamic limit.

Processing and probing of icy molecules on Satellite surfaces

Date: 2017-04-28
Speaker: Mr. Rahul Kumar Kushwaha
Venue: Room No: 006, PRL Thaltej

Abstract

Magnetohydrodynamic Modeling of Solar Coronal Dynamics with an Initial Non-force-free Magnetic Field

Date: 2017-04-27
Speaker: Dr. Avijeet Prasad
Venue: USO Seminar Hall

Abstract

Generalizing Einstein's derivation of Planck's black-body radiation formula to non-equilibrium systems: the new concept of electro-magneto resistance.

Date: 2017-04-27
Speaker: Dr. Navinder Singh
Venue: Room No. 469

Abstract

In this first work under PRL's TDP project (No. TDP-ESR-623) we generalize the magneto-resistance phenomenon where the resistivity of materials change under a transverse magnetic field to a regime where in addition to magnetic field there is also a transverse ac field of resonant frequency with the Zeeman splitting. Our theoretical calculations predict this effect and the experiment to test it is under development (under TDP project). The idea is the following. In a magnetic field, electron spin levels are Zeeman split. If a resonant ac field is applied there is a new channel of momentum relaxation. An additional resistivity is predicted. The whole work is based upon a generalization of the Einstein's derivation of Planck's black-body radiation formula to non-equilibrium systems. This talk will summarize the theory work.

Quantifying the accuracy and precision of difference-smoothing algorithm for time delay measurement using simulated light curves from TDC1

Date: 2017-04-27
Speaker: Dr. S. Rathna Kumar
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Measurement of time delays between the images of gravitationally lensed quasars has been demonstrated to be a competitive method to constrain cosmological parameters. During the next decade, the Large Synoptic Survey Telescope (LSST) is expected to discover and monitor on the order of thousand lensed quasars. Hence it is of interest to develop time delay measurement algorithms that are not only fast, but also accurate and precise. In this talk, I shall describe a recent effort to rigorously test the difference-smoothing algorithm on a large sample of simulated light curves from the first edition of Strong Lens Time Delay Challenge (TDC1) and the refinements that were required to make it competitive with the best performing algorithms of TDC1. I shall also briefly touch on the upcoming TDC2, which is expected to address the problem of reliably measuring time delay from a combination of multi-filter light curves as expected from LSST.

Status of 1MeV PRL- Accelerator Mass Spectrometer (AMS) for the Measurement of 14C, 26Al and 10Be.

Date: 2017-04-25
Speaker: Dr. Ravi Bhushan
Venue: Ground Floor Lecture Hall

Abstract

A New Accelerator Mass Spectrometry (AMS) Laboratory has been successfully installed at PRL-Thaltej Campus dedicated for the measurement of 14C, 10Be and 26Al. This facility has been acronymed as PRL AURiS (Physical Research Laboratory Accelerator Unit for RadioIsotope Studies). The 1 MeV AMS system manufactured by High Voltage Engineering Europa B.V., The Netherlands comprises: (1) Ion source for production of negative ions (2) Low Energy Mass Spectrometer for the selection and injection of isotopes of interest, (3) 1 MeV Tandetron Accelerator for acceleration and Argon gas for molecular stripping, (4) High Energy Mass Spectrometer for focussing the isotopes leaving the accelerator into the Faraday Cups and towards the Ionisation detector, (5) 120o Electrostatic Analyser (ESA) for focussing and further filtering followed by (6) a Low Background Magnet, and the Ionisation Detector for the measurement of the rare isotopes. Additionally, Automated Graphitisation Equipment (AGE3) for preparation of carbon samples as graphite for AMS measurement has been installed. The AMS facility can measure 14C, 10Be and 26Al and would contribute towards the various research programmes in Oceanography, Geology, Climate Studies, Archeology, Hydrology and Planetary Sciences. Preliminary results obtained on performance of PRL AURiS would be presented.

Waves in the Earth’s atmosphere

Date: 2017-04-24
Speaker: Subir Mandal
Venue: Ground Floor Lecture Hall

Abstract

Various kinds of waves and oscillations are present in the Earth’s atmosphere. Atmospheric waves are of different spatial and temporal scales, and are in general, generated in lower atmosphere. They carry energy and momentum from their source regions as they propagate to upper atmospheric altitudes. The breaking of waves is associated with release of energy in the background atmosphere, and hence the waves in Earth’s atmosphere play a crucial role in the coupling processes of different atmospheric regions. A broad introduction of different types of waves and their characteristic properties will be given. Observations of such wave features (mainly gravity waves) on different atmospheric parameters (e.g., temperature, wind, neutral and plasma densities, etc.) will be presented.

The Noncommutative Standard Model and its phenomenology

Date: 2017-04-21
Speaker: Mr. Selvaganapathy J
Venue: Room No. 469

Abstract

The existence of the principles of Quantum Mechanics and of Classical General Relativity points some difficulties at the small scale: the space-time uncertainty emerges from the Heisenberg principle, thereby suggesting that space-time has a quantum structure at small length scale: the space-time becomes fuzzy i.e. noncommutative(NC) at this scale. One of the property of the NC theory is that it is nonlocality inherent, which includes the gravity with standard model naturally. There is no theoretical prediction for energy scale at which noncommutative effects arise. So the energy scale can ranges from TeV scale to Planck scale. In this talk I would like to give a brief description about the non-commutative standard model (NCSM) and a phenomenological survey of this model. In particularly, I would like to discuss about neutral triple gauge boson interaction at LHC.At the end, I would like to discuss about the Drell-Yan process in the NCSM.

New Physics searches in radiative charm decays

Date: 2017-04-20
Speaker: Dr. Aritra Biswas
Venue: Room No. 469

Abstract

We show that for a heavy vector-like quark model with a down type isosinglet, branching ratio for c--> u gamma decay is enhanced by more than O(10^2) as compared to that in the Standard model when QCD corrections to next-to-leading order are incorporated. In a left-right symmetric model (LRSM) along with a heavy vector-like fermion, enhancement of this order can be achieved at the bare (QCD uncorrected) level itself. We propose that a measurement of the photon polarization could be used to signal the presence of such new physics inspite of the large long distance effects. We find that there is a large region within the allowed parameter space of the LRSM, as well as in the model with vector-like quark with additional left-right symmetry, where the photon polarization can be dominantly right-handed.

Xray/UV/Optical variability in Seyfert 1 galaxies

Date: 2017-04-20
Speaker: Dr. Main Pal
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Active galactic nuclei (AGN) are the most luminous, long-lived and highly variable sources in the Universe. These objects emit almost over entire electromagnetic spectrum. In case of Seyfert type 1 AGN, the UV/optical to X-ray spectrum consists of complex spectral components such as powerlaw, soft X-ray excess below ~2 keV, iron- K lines near 6 keV, Compton hump in 10-50 keV and big blue bump (BBB) in the UV/optical bands. These components can be used to probe the unresolved central engine and various physical processes in the vicinity of the supermassive blackhole. The variability nature of these features in the X-ray to UV/optical bands are less well understood. I will discuss these components and their relationship through spectral and timing variability study in detail in Seyfert 1 galaxies such as 1H 0419-577, II Zw 177 and Fairall 9.

Brown Carbon Characteristics during Paddy-Residue Burning over the Indo-Gangetic Plain

Date: 2017-04-18
Speaker: Mr. Satish R V.
Venue: Ground Floor Lecture Hall

Abstract

Atmospheric carbonaceous aerosols consisting of black carbon (BC) and organic carbon (OC) influence Earth’s radiative balance by interacting with the solar radiation. The role of BC in the atmosphere is reasonably well understood and incorporated into climate model studies. On the other hand, OC considered as “white” for many years because they efficiently scatter visible radiation. Recent findings suggest that a significant part of organic aerosols absorbs light at near UV and visible region and termed as Brown Carbon (BrC). To assess the role of BrC on regional/global level, it is inevitable to understand their sources and characteristics on temporal and spatial scale. However, such studies are very limited in literature. This study presents the BrC spectral characteristics and chemical composition of PM2.5 samples collected before, during and after a large scale paddy-residue burning over Patiala (30.2oN, 76.3oE), located in the northwestern IGP during October-November, 2014. Results from this study will be discussed.

Principle of Proton Transfer Reaction-Time of Flight-Mass Spectrometry (PTR-TOF-MS): Measurements of Ambient VOCs

Date: 2017-04-17
Speaker: Nidhi Tripathi
Venue: Ground Floor Lecture Hall

Abstract

Volatile organic compounds (VOCs) are ubiquitous trace gases in the global troposphere. VOCs are emitted from a variety of natural and anthropogenic sources. VOCs are precursors of ozone and secondary organic aerosols (SOA) and hence are important species from climate change perspective. VOCs control the oxidizing capacity of the troposphere mainly due to fast reactions with hydroxyl (OH) and other radicals. Measurements of VOCs are technically challenging due to fast reactivity and low concentrations in the atmosphere. In recent years, Proton Transfer Reaction-Mass Spectrometry (PTR-MS) has emerged as a robust technique for accurate and fast measurements of many VOCs present in air. In my presentation, I will discuss the important aspects of the Proton Transfer Reaction-Time of Flight-Mass Spectrometer (PTR-TOF-MS) which is an innovative technology for high time- and mass- resolution measurements of VOCs.

Generation of Supercontinuum light, Modulational Instability and Entangled Photon Pair Using Photonic Crystal Fiber

Date: 2017-04-13
Speaker: G. Joshva Raj
Venue: Room No: 113, PRL Thaltej Campus

Abstract

The talk will be started with the presentation of my Ph.D thesis which is entitled as “A Theoretical Study on the Effect of Temperature on Supercontinuum Generation and Modulational Instability in Liquid-core Photonic Crystal Fiber”. The generation of supercontinuum light and modulational instability in photonic crystal fiber will be explained. The investigation of the effect of temperature on such highly nonlinear phenomena will be detailed. The possibility of using temperature as a control parameter in order to tune the bandwidth of broadband spectrum will be discussed. Following the thesis presentation, a research proposal on the studies on entangled photon pair generation using spontaneous four-wave mixing in erbium doped photonic crystal fiber will be discussed. An useful application of optical fibers is the production of entangled photon pairs using FWM. Various types of fiber have been investigated in the context of FWM assisted entangled photon pairs. In this line, the necessity of investigating erbium doped photonic crystal fiber as a medium to generate entangled photon pairs will be discussed. The methodology and the techniques that are required to carry out the investigation of four-wave mixing in erbium doped photonic crystal fiber in the quantum realm will be explained.

Reinvestigation of the laser cooling mechanism — statistical distributions and anomalous diffusion in optical lattices

Date: 2017-04-10
Speaker: Prof. Anders Kastberg
Venue: Room 469, fourth floor, PRL Main building

Abstract

In this seminar, I will review the physical processes leading to ”sub-Doppler” temperatures in laser cooled atom. These processes are generally accepted to be well described by sop called ”Sisyphus cooling”. However, recent experimental and theoretical findings show that the Sisyphus model is at best a partial explanation for the relevant light-atom interaction. Aside from the purely academic question about the nature of the cooling process, there are indications, partially controversial, that the ensuing momentum distribution in the atomic cloud follows a power law. This could in turn makes such samples good candidate for fundamental studies of anomalous diffusion and non-ergodicity. Moreover, the acute sensitivity of the cooling process on the exact atomic structure may also provide a tool for precession spectroscopy.

Magnetic fields and waves in the lower solar atmosphere, and difficulties in local helioseismology

Date: 2017-04-06
Speaker: Prof.S.P. Rajaguru
Venue: USO Seminar Hall

Abstract

Texture Zero studies for the minimal extended type-I seesaw mechanism

Date: 2017-04-04
Speaker: Newton Nath
Venue: Room No. 469

Abstract

In this talk, we will discuss about the minimal extended type-I seesaw (MES) model which can give rise to eV scale sterile neutrino. In this model, three right handed neutrinos and one extra singlet S are added to generate a light sterile neutrino. We study the zero textures of the Yukawa matrices for the MES model. Remarkably we obtain only two allowed one-zero textures namely, m_{e\tau} = 0 and m_{\tau\tau}=0 having inverted hierarchical mass spectrum. We also discuss the importance of next-to-leading order correction terms in this model.

Latest updates on proxy records of Sunspot activity in the Holocene and the early Permian.

Date: 2017-04-04
Speaker: Dr. M. G. Yadava
Venue: Ground Floor Lecture Hall

Abstract

Cyclicity in time series of climate proxies, belived to be of solar origin, is documented in the high resolution archives such as ice cores or tree rings in the present and the geological past. The smallest cycle with 11 yrs periodicity is attributed to the sunspot activity and has a measurable effect on the Earth’s climate as shown by the Maunder minimum. Indian rainfall also shows 11yr periodicity, in the modern rainfall and the proxy data from climate archives. It seems that 11 yr solar cycle has been affecting the Earth’s climate over hundreds of million years by holding its stable periodicity over time. Some of the proxy based evidences will be presented to discuss a debatable topic, which needs continued investigation for better understanding.

On Wave Breaking / Phase mixing of Relativistically Intense Longitudinal Waves in a Plasma

Date: 2017-03-30
Speaker: Prof. Sudip Sengupta
Venue: Room No. 469

Abstract

The study of the spatio-temporal evolution of a large amplitude longitudinal plasma oscillation or wave is a topic of fundamental importance in non-linear plasma physics. The amplitude of these nonlinear plasma waves is limited by a phenomenon called wave breaking, which may be induced by several physical processes. In this talk, along with a brief overview, current understanding of wave breaking of relativistically intense waves in a cold plasma will be presented. Extension to the warm plasma case in the non-relativistic limit will also be discussed.

Stream power: A unified concept in fluvial geomorphology

Date: 2017-03-28
Speaker: Dr. Vikrant Jain
Venue: Ground Floor Lecture Hall

Abstract

Last two decades have witnessed major advancements in the quantitative understanding of geomorphological processes at different spatio-temporal scales. Modelling of geomorphic processes needs well defined geomorphic transport law(s) for different geomorphic systems. Studies in fluvial geomorphology has benefitted by a concept of stream power, which is a fundamental parameter to define driving force at any scale. It was incorporated in geomorphic studies from sixties through a study of sediment transport (Bagnold, 1966*). Subsequently, the stream power concept has been successfully applied to model various processes at different scales ranging from sand particle movement to landscape evolution processes. My talk will highlight the significance of unified concept in a geomorphic system, which led to integrate processes at different scales. The work will highlight new advancements and challenges in this research area. *Bagnold, R.A., 1966. An approach to the sediment transport problem from general physics. Geological Survey Professional Paper 422-I, I1– I37.

Solar wind high-speed stream impacts on the Earth and comet

Date: 2017-03-27
Speaker: Dr. Rajkumar Hajra
Venue: Ground Floor Lecture Hall

Abstract

The solar coronal holes emanate high-speed (~750-800 km s-1) streams (HSSs). If the coronal holes last for more than a solar rotation period (~27 days), the corresponding HSSs appear to “corotate” with the sun, very much like water spewing from a lawn sprinkler. These HSSs, when they interact with slow-speed (~300-400 km s-1) streams near the ecliptic plane, give rise to compressed plasma and magnetic field regions, the so-called corotating interaction regions (CIRs). The HSSs/CIRs are characterized by nonlinear interplanetary Alfvén waves. In the present talk I will show recent results on the CIR/HSS impacts on the near-Earth and cometary plasmas. The Earth’s magnetosphere and the cometary plasma without any intrinsic magnetic fields exhibit distinguishing interactions with the solar winds.Earth orbiting satellite and ground based observations will be presented to show the impacts on the Earth’s magnetosphere-ionosphere system.The solar wind impacts on the induced magnetosphere of the comet will be shown based on the observations made by the ESA’s Rosetta spacecraft that in situ monitored the target comet 67P/Churyumov-Gerasimenko for more than 2 years.

BIOGEOCHEMISTRY OF ASIA’S LARGEST LAGOON

Date: 2017-03-21
Speaker: Ms. Rupa Mukherjee
Venue: Ground Floor Lecture Hall

Abstract

Wetlands, lakes and lagoons play a central role in regional hydrologic and biogeochemical cycles, in maintaining biodiversity, and in a wide range of human activities. Chilika lagoon, the Asia's largest brackish water lagoon with estuarine character is a very important ecosystem in terms of ecology as well as economy. The talk will focus on the various ecological as well as environmental parameters of the lagoon which has been studied in 2004-2006 along with present understanding of the delta-13-C and delta-15-N isotopic signatures and N uptake rates.

Fermionic dark matter and supernova SN1987A cooling

Date: 2017-03-21
Speaker: Dr. Prasanta K Das
Venue: Room No. 469

Abstract

Light dark matter(1 − 30 MeV) particles which can be pair produced in electron-positron annihilation e − e + −→ χ χ inside the supernova SN1987A core take away the energy released in the supernova SN1987A explosion. Using the Raffelt’s criteria on the energy loss rate and using the optical depth criteria on the free streaming of the dark matter fermion, we find that the lower bound on the scale Λ of the dark matter effective theory to be Λ ∼ 10 8 TeV for m χ = 30 MeV. We extend our study in q-deformed statistics scenario and study the impact of it on the scale Λ .

Two new avenues in dark matter indirect detection

Date: 2017-03-21
Speaker: Dr. Ranjan Laha
Venue: Room No. 469

Abstract

Indirect detection is one of the major ways to search for dark matter. However, backgrounds have been a major problem for these searches. In this talk, I will introduce two new techniques to distinguish signal from background. Firstly, I will show how telescopes with ~ 0.1% energy resolution can exploit the Doppler shift of sharp photon features arising from dark matter interactions and separate the signal from background. The technique is general and I will give an example of this search strategy with the 3.5 keV line. In the second half of my talk, I will show how limits from the searches for very high energy photons can be used to constrain dark matter interactions. Using this observable, I will constrain very heavy dark matter which is very difficult to constrain using other means.

Pan-Starrs followup of Planck SZ clusters & Galactic Shapiro delay of Gravitational Waves

Date: 2017-03-20
Speaker: Dr. Shantanu Desai
Venue: Room No. 469

Abstract

The first half of the talk shall present results of a study of Planck Sunyaev-Zel'dovich effect selected galaxy cluster candidates (from their 2013 data release) using the Pan-STARRS imaging telescope in Hawaii. We were able to confirm about 60 galaxy clusters and measure the photometric redshifts with an accuracy of about 2.2%. The second half of the talk will discuss the practical implications of the line of Shapiro delay of gravitational waves, results from GW150914 and will discuss the relevance of Shapiro delay for the detection of EM counterparts of GW sources.

Direct transfer of classical non-separable state into hybrid entangled two-photon state

Date: 2017-03-17
Speaker: Mr. Jabir M V
Venue: GF Lecture Hall

Abstract

Hybrid entangled states, having entanglement between different degrees-of-freedom (DoF) of a particle pair, are of great interest for quantum information science and communication protocols. Among different DoFs, the hybrid entangled states encoded with polarization and orbital angular momentum (OAM) allow the generation of qubit-qudit entangled states, macroscopic entanglement with very high quanta of OAM and improvement in angular resolution in remote sensing. Till date, such hybrid entangled states are generated by using a high-fidelity polarization entangled state and subsequent imprinting of chosen amount of OAM using suitable mode converters such as spatial light modulator in complicated experimental schemes. Given that the entangled sources have feeble number of photons, loss of photons during imprinting of OAM using diffractive optical elements limits the use of such hybrid state for practical applications. Here we report, on a simple experimental scheme to generate hybrid entangled state in polarization and OAM through direct transfer of classical non-separable state of the pump beam in parametric down conversion process. As a proof of principle, using local non-separable pump state of OAM mode l=3, we have produced quantum hybrid entangled state with entanglement witness parameter of = 1.25ą0.03 violating by 8 standard deviation. The generic scheme can be used to produce hybrid entangled state between two photons differing by any quantum number through proper choice of non-separable state of the pump beam.

Expeditions for Physics Beyond the Standard Model : Challenges and Prospects

Date: 2017-03-16
Speaker: Dr. Satyanarayan Mukhopadhyay
Venue: Room No. 469

Abstract

The energy, intensity and cosmic frontiers constitute the three major directions of research in particle physics, driven by a large number of ongoing and upcoming experimental and observational probes. Efforts to explore physics beyond the standard model at these experiments give rise to two challenging tasks : (1) how to dig out a tiny signal from a huge background using our understanding of known physics and (2) how to interpret the experimental results from a vast range of probes within an unified theoretical framework. I shall describe progress in addressing the first challenge using examples from the search for strongly interacting new particles at the LHC in difficult to access kinematic regimes. On the second challenge, I shall take up the case-study of classifying and understanding the different probes of particle dark matter, both within the framework of effective field theory as well as in specific simple models.

Constraining the exhumation history of the Nagaland ophiolite complex

Date: 2017-03-07
Speaker: Dr. B. Maibam
Venue: Ground Floor Lecture Hall

Abstract

The current understanding of the tectonic significance of blueschist-facies rocks associated with the Indo-Myanmar ophiolite belt is unclear due to a lack of systematic petrological study and the paucity of reliable age data. During the talk, I would present new integrated petrological and geochronological data for samples from the Nagaland complex of the Indo-Myanmar ophiolite belt, northeastern India, which constrains the pressure–temperature conditions and ages of peak and retrograde metamorphism

An Impact of FORMOSAT-3/COSMIC (GPS) Soundings for the prediction of severe weather systems

Date: 2017-03-03
Speaker: Dr. Anisetty S. K. A. V. Prasad Rao
Venue: Ground Floor Lecture Hall

Abstract

Global Position System(GPS) soundings are assimilated to explore the impacts of GPS data on prediction of super Cyclone Gonu in 2007. Other data, including satellite data, radiosonde soundings and bogus vortex are also assimilated to highlight the relative contribution of GPS data to model prediction. Cyclone Gonu formed in the south central Arabian Sea and tracked west-northwestward into the Straights of Hormuz, reaching a peak intensity of 145 knots and a minimum sea-level pressure of 898 hPa before making a landfall in Iran. A series of experiments initialized with GPS refractivity from FORMOSAT-3/COSMIC (GPS), Special Sensor Microwave Imager (SSM/I) retrieved precipitable water and near-surface oceanic wind speed, GTS, QuickScatterometer (QuikSCAT) and bogus vortex are assessed by the model prediction using the advanced Weather Research and Forecasting (WRF) model with three dimensional variational data assimilation (3DVAR) to ingest these observations. Significant differences in cyclone track and intensity prediction are observed in various assimilations. GPS experiment outperforms other experiments in track prediction, while SSM/I improve intensity prediction. Sensitivity tests were conducted to identify which GPS soundings play a more important role in improvement of track prediction. It was found that the GPS soundings in the vicinity of Gonu vortex appear to modulate the environmental moistening conditions that lead to the impact on track prediction. Other sensitivity experiments show that retrieved GPS data information at upper levels greatly contributes to track prediction.

GRB Polarization using AstroSat CZTI

Date: 2017-03-02
Speaker: Ms. Aarthy E
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Gamma Ray Bursts are the most powerful explosions observed so far in the universe since the Big Bang. Since the time it was discovered, over the past 4 decades the field of GRBs has grown tremendously with the advent of several missions like CGRO/BATSE, Swift, Fermi etc and other ground based observatories. Although, there are still unanswered questions related to the prompt emission (initial burst of gamma rays), the emission mechanism behind the inner most region of the relativistic jets. And measuring GRB Polarization could take this one step further. CZTI onboard AstroSat has an added advantage of being a GRB monitor and has capabilities to measure polarization at energies > 100 keV. I would brief about the current understanding of GRBs, how CZTI works as a polarimeter, and also would present the polarization results we have obtained for few GRBs using CZTI.

Depositional Environment of the Paleogene sequences of Jaisalmer basin, Rajasthan, Western India.

Date: 2017-02-21
Speaker: Dr. Amitava Patra
Venue: Ground Floor Lecture Hall

Abstract

The Jaisalmer basin is the eastern extension of the shelf part of the Indus Basin and represents a more or less central part of the "West Rajasthan Shelf"tectonic province that is located to the west of the Aravalli ranges. The Paleogene succession of the Jaisalmer basin has hydrocarbon potential. This succession is dominantly represented by calcareous and argillaceous rocks with a subordinate proportion of arenites in the basal part. The facies associations suggest a complete 2nd order cycle of transgression-regression of the sea from shoreface to tidal flat in the Jaisalmer pericratonic basin. Provenance of the late Paleocene sandstone of the Jaisalmer basin has been determined by petrographic and heavy minerals analysis supported by paleocurrent study.Q-F-L and Qm-F-Lt diagrams suggest for a provenance at the margin of the craton interior and transitional continental. All these suggest that the provenance was dominated by low to medium grade metamorphic and volcanic rocks of the Aravalli Supergroup, Jurassic succession and the Deccan basalts which were denuded during late Paleocene.

Astrochemistry @ 2016: A review and where we stand

Date: 2017-02-17
Speaker: Dr. Bhalamurugan Sivaraman
Venue: Thaltej Room No. 6 (Main building)

Abstract

Heavy quark dynamics in RHIC and LHC

Date: 2017-02-17
Speaker: Dr. Santosh Kumar Das
Venue: Room No. 469

Abstract

The heavy quarks, charm and bottom, constitutes a unique probe of the quark gluon plasma (QGP) properties. Both at RHIC and LHC energies a puzzling relation between the nuclear modification factor RAA(pT) and the elliptic flow v2(pT) related to heavy quark has been observed which challenged all the existing models. We discuss how the temperature dependence of the heavy quark drag coefficient is responsible to address for a large part of such a puzzle along with the full solution of the Boltzmann collision integral for the momentum evolution of heavy quarks in the medium. Ultra-relativistic Heavy-Ion Collision (HIC) also generates very strong initial magnetic field. Since the heavy quark are produced at the early stage of HICs, we argue that their dynamics will be affected by such a strong magnetic field and we demonstrate that the directed flow, v1 , of heavy quarks is a superior probe to estimate the magnetic field generated in non- central HICs. We show that the resultant effects entail a significantly large v1 of charm quarks which is about two order of magnitude larger than the light quarks v1 and can be measured at experiments.

Bayesian Inference : An Approach in Astronomy

Date: 2017-02-16
Speaker: Ms. Archita Rai
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Statistical methods of data analysis have been used in science since centuries, with slight modifications which can be traced to the same school of thought – the Bayesian approach (1763). In the astronomical domain, usage of Bayesian statistics has started in the last few decades and since then it is considered to be the most referred one by researchers in this field. The Bayesian method is an application of the Bayes' theorem. Bayes' theorem provides the conditional probability of the happening of an event given that another event has taken place. When applied to models used to fit a particular data set, it helps in getting the model parameters which best fits the observed data. Bayesian statistics, hence, deals with the data that were actually observed. With a brief overview of probability, the talk will try to explain the 'Bayesian recipe' with a detailed look on the different probability distributions from prior to posterior involved in it. The Bayesian approach towards data sets and model selection will also be discussed with its application in astronomy. The Bayesian inference method exemplifies the statement : 'It is vain to do with more what can be done with less'.

A review of PRL’s journey towards measurement of nitrogen transformation rates.

Date: 2017-02-14
Speaker: Dr. Sanjeev Kumar
Venue: Ground Floor Lecture Hall

Abstract

MANY BODY ASPECTS OF GRAVITY IN COMPACT STARS

Date: 2017-02-09
Speaker: Prof. M. Azam
Venue: Room No. 469

Abstract

Compact stars such as neutron stars and black holes are gravitationally bound many body systems. We investigate the importance of short and long range part of gravity for such systems. From our analysis, we conclude that the true essence of gravity lies with the long range nature of the interaction.

Reconstruction of Mid-Late Holocene Land-Sea interaction using Sulfur Isotopes as a new tracer

Date: 2017-02-07
Speaker: Dr.Upasana Banerji
Venue: Ground Floor Lecture Hall

Abstract

Sea level varied throughout the geological past where eustatic and/or tectonic change played significant role in controlling the sea level. Unlike glacial and interglacial periods, no major sea level fluctuations have been observed during mid-late Holocene period. Thus, reconstruction of local sea level history rather than accepting global sea level change remains a challenge. Various studies have addressed mid-late Holocene sea level changes but only few could delineate the tectonic component involved in it. Saurashtra coast provides an ideal platform to study Holocene land-sea interactions. The southern Saurashtra coast consists of extensive mudflats which can provide a continuous record of sea level change. Sulphur isotope (delta 948;34S) has played a crucial role in constraining the biogeochemical cycle in modern environment and proven to be a valuable tool in unravelling the early history of earth surface oxidation. The talk will address local tectonic event deciphered from sulfur isotopes supported by productivity and redox proxies that resulted in local sea level change during mid-late Holocene period.

Paschen-Back effect in atomic states as a tool for magnetic field diagnostics

Date: 2017-02-07
Speaker: Sowmya K.
Venue: USO Seminar Hall

Abstract

Generation of vortex dipole from the doubly resonating optical parametric oscillator

Date: 2017-01-27
Speaker: Varun Sharma
Venue: GF Lecture Hall

Abstract

In recent times, vortex dipoles have created a lot of interest in studying in propagation dynamics and optical vortex meteorology. Typically, optical vortex dipoles are created using holographic techniques. But recently we have generated the vortex dipole using an optical parametric oscillator (OPO) while pumping with Gaussian beam in the green, this doubly resonant OPO produces vortex dipole tunable across the wavelength range 968-1181 nm.

Bridging Macro and Micro Physical Scales in Astrophysical Jets using Numerical Simulations.

Date: 2017-01-19
Speaker: Dr. Bhargav Vaidya
Venue: Room - 113/114, Thaltej Campus

Abstract

Jets and Outflows is a universal phenomenon that marks the onset of active accretion process in various astrophysical objects. With an aim to connect macro-physical models and create a synthetic observatory for such astrophysical jets, numerical simulations should incorporate effects due to microscopic processes. In this talk, I will focus on two such microscopic processes, viz. thermo-chemical evolution and particle acceleration, that have been implemented in the PLUTO code. The thermo-chemical module accounts for combining fluid dynamical models with chemical evolution in presence of consistent Equation of State (EoS). I will present results on applying this module to study molecular outflows in young stellar objects. Further, in order to study physics of particle acceleration and multi-wavelength emission from AGN jets, I will present an implementation of a fully parallel, hybrid framework that allows the evolution of Lagrangian particles coupled to relativistic MHD flows. A spectral evolution study in conjunction with propagation of particles through regions of varying magnetic field and associated radiative processes like synchrotron emission, Inverse Compton provides a consistent picture of particle energetics.

The tale of Phosphorus-the devil's element

Date: 2017-01-17
Speaker: Dr. Bhavya P. S.
Venue: Ground Floor Lecture Hall

Abstract

The discovery of phosphorus was an accident while all the alchemists in 17th century were behind the mythological substance, the philosopher's stone. This light bearing substance later on became part of many revolutionary changes in the modern human history. The eventual entry of Haber-Bosch process led to green revolution which enhanced the crop production as well as population density. However, excess nutrient usage led to aquatic eutrophication. The talk will address the revolutionary developments in the history of biogeochemistry after the finding of phosphorus, the devil's element. The talk will also give glimpses of mitigation strategies which have been developed in the past few decades to control the aquatic pollution.

Exploration of the second solar spectrum through polarimetric studies

Date: 2017-01-17
Speaker: Ms. Supriya H D
Venue: USO Seminar Hall

Abstract

Forces governing CME propagation

Date: 2017-01-13
Speaker: Prof. Prasad Subramanian
Venue: USO Seminar Hall

Abstract

Karoo CFB, Southern Africa-Evolved From MORB By Mixing With A-Type Rhyolite In Bimodal Association

Date: 2017-01-10
Speaker: Dr. Saumitra Misra
Venue: Ground Floor Lecture Hall

Abstract

The ~183 Ma Karoo CFB of southern Africa is a part of the Karoo-Ferrar-SE Australia Large Igneous Province, which is believed to erupt behind the convergent Pacific margin during the break up of Pangea between ~200-175 Ma. Integrated petrographic and geochemical study suggests that magma mixing had an important role in the geochemical evolution of Karoo CFB, and imprinted a lithospheric signature on the Karoo basalts. The Karoo CFB evolved from the MORB-like parent magma through mixing with bimodal rhyolitic magma and hence does not require a mantle plume hypothesis.

Quasi-biennial oscillation modulation of semidiurnal tides

Date: 2017-01-09
Speaker: Dr. Mahesh Sha
Venue: Ground Floor Lecture Hall

Abstract

The remote sensing technique is an important tool for probing greenhouse gas cycles in the Earth’s atmosphere. This talk will focus on the solar absorption measurement techniques for the study of sources and sinks of greenhouse gases thereby entangling the issue of global warming, which is one of the major concerns for the survival on Earth. The key challenge of this method is the high accuracy and precision requirements of the measurements, as it is the minute change in the concentration of the greenhouse gases which has to be detected on top of large background concentrations. The talk will address the existing ground-based infrared remote sensing greenhouse gas observation networks and their use for the validation of models and greenhouse gas measurements from satellites.

Uncertainty Relations Beyond Heisenberg's

Date: 2017-01-09
Speaker: Prof. A. K. Pati
Venue: GF Lecture Hall

Abstract

The famous uncertainty relation introduced by Heisenberg is a basic feature of quantum theory enshrined in all textbooks. The rigorous form of the Heisenberg-Robertson uncertainty relation expresses a limitation in the possible preparations of the system by giving a lower bound to the product of the variances of two observables in terms of their commutator. However, it does not capture the concept of incompatible observables because it can be trivial, i.e., the lower bound can be null even for two incompatible observables. Here, we will prove two stronger uncertainty relations, relating to the sum of variances, whose lower bound is guaranteed to be nontrivial whenever the two observables are incompatible on the state of the system. These "stronger uncertainty relations" go beyond the Heisenberg-Robertson relation and suggest that quantum mechanical uncertainties respect more stringent bounds than what is thought before.

2016

Charged Higgs search prospects in bosonic decays

Date: 2016-12-30
Speaker: Dr. Pankaj Sharma
Venue: Room No. 469

Abstract

Anticipated in the current and future runs of the LHC is the discovery of a charged Higgs which would be an unequivocal evidence for new physics. In this talk, I will review the prospects of the LHC in accessing heavy charged Higgs boson signals in bbW final states, wherein the contributing channels can be H \to tb, hW, HW and AW. In particular, we devise a selection strategy which optimizes their global yield. We consider a 2-Higgs Doublet Model Type-II and we assume as production mode bg → tH− + c.c., the dominant one over the range MH ≥ 480 GeV, as dictated by b → sγ constraints. We further make use of jet substructure techniques for Higgs tagging and multivariate techniques such as boosted decision trees in order to maximize the discovery potential of charged Higgs in its bosonic decays.

Mixed fermion dark matter, neutrino mass and collider signature

Date: 2016-12-29
Speaker: Dr. Narendra Sahu
Venue: Room No. 469

Abstract

The galaxy rotation curve, gravitational lensing and the existence of large scale structure imply that the present Universe is filled with a mysterious form of matter, called “dark matter (DM)”,which is about 27% ( roughly 5 times of visible matter) of the total energy budget. Hitherto the existence of DM is obtained via its gravitational interaction in a large scale, starting from galaxy size. The main challenge at present is to probe the DM in a small scale, typically in an earth bound laboratory. The only information so far we know about DM is its relic density. However, the microscopic structure of DM is completely unknown. Unfortunately the standard model (SM) of particle physics, the best model that describes the fundamental interactions of visible matter, does not accommodate any such particle. In this talk we explore certain aspects of physics beyond the SM to include dark matter as well as non-zero neutrino mass, confirmed by oscillation experiments. In particular, we extend the SM by including a mixed singlet-doublet fermion dark matter and obtain the parameter space for testing the hypothesis at collider.

Impact of Different Types of Prompt Penetration Electric fields (PPE) Over Low Latitude Ionosphere-Thermosphere System

Date: 2016-12-26
Speaker: Diptiranjan Rout
Venue: Ground Floor Lecture Hall

Abstract

The PPE plays an important role in redistributing the plasma in the magnetosphere-ionosphere system during different space weather events. Evaluating the effects of PPE is important as these can significantly alter global as well as low latitude ionospheric electrodynamics. Some of the results presented in this talk are observed and reported for the first time. Using multi-instrument global observations, it will be discussed that how PPE can affect the low latitude ionosphere-thermosphere system (ITS) not only during storms and substorms, but even when solar wind density changes by a small amount. In addition, the effects of PPE corresponding to the passage of a sheath region associated with Interplanetary Coronal Mass Ejection (ICME) will be shown.

The effect of nuclear charge distributions on the Isotope Field Shift in Ca+

Date: 2016-12-26
Speaker: Pradeep Kumar
Venue: GF Lecture Hall

Abstract

Motivated by a recent observation of unusually large differences between the measurement and theoretical studies on the field shift ratio of the D_2 and D_1 lines in the Ca^+ ion, we investigate the role of the nuclear charge distribution in the determination of the field shifts. In my talk, I shall discuss about the theoretical results of the field shift constants obtained from both the uniform and Fermi nuclear charge distributions. To validate the results, calculations are carried out using two distinct procedures as finite gradient approach and evaluation of the expectation value in the perturbative framework. At the end, I shall also highlight possible scopes to remove discrepancies between the experimental and theoretical results further.

Corals - unfolding the history of tropical oceans

Date: 2016-12-20
Speaker: Mr. Harsh Raj
Venue: Ground Floor Lecture Hall

Abstract

Paleoclimatic reconstruction is important for understanding climate and its variations. Geochemical and isotopic proxies have been effectively used to study past climatic variations as they record changes in different properties of ocean. Corals provide unaltered high-resolution records of such proxies. Events like ENSO (El Nino Southern Oscillation) and IOD (Indian Ocean Dipole) observed in tropical Pacific Ocean and Indian Ocean respectively are result of amplified climatic variation. Such events have enormous socio-economic impacts globally and require better understanding. delta-18-O, delta-13-C and delta-14-C in coral skeleton are some of the potential tracers which acts as a proxy indicator of variations in SST, salinity, upwelling, rainfall etc. This presentation highlights use of geochemical proxies in corals for paleoclimatic reconstruction. Possibility of using these proxies to identify ENSO and IOD signatures in context of my proposed research plan would also be discussed.

The Inner Gaseous Disks of Herbig Be Stars

Date: 2016-12-15
Speaker: Dr Parshati Patel
Venue: Room-113/114, Thaltej Campus

Abstract

Herbig Ae/Be (HAeBe) stars are massive pre-main sequence stars known to have disks and envelopes around them. These disks are inherited by the star from the star formation phase and can generally be divided into two regions: gaseous and dusty. The disk region close to the star experiences intense radiation, creating high-temperatures and leading to sublimation of the dust and an entirely gaseous region. This part of the disk, also known as dust-free zone, is poorly understood. This inner gaseous disk could be very similar to the disks around other hot stars such as Classical Be stars, whose disks are reasonably well understood. Using the circumstellar disk codes, BEDISK and BERAY, to model observed optical and near-infrared spectra from the ESPaDOnS instrument on Canada-France-Hawaii Telescope, we attempt to constrain the physical properties of the inner gaseous region. The photoionizing radiation of the central star is assumed to be the sole source of input energy for the disk. I will present the results from our study of four early-type Herbig Be stars

Coherent generation, control and manipulation of structured beam in atomic vapor

Date: 2016-12-13
Speaker: Dr. Tarak Nath Dey
Venue: GF Lecture Hall

Abstract

A novel scheme for coherent generation, control and manipulation of structured beams in a system of homogeneously broadened atomic vapor with atoms in a closed three-level Λ-configuration has been used to explain the recent experimental results of Radwell et al. Phys. Rev. Lett. 114, 123603(2015). The key feature underlying structured beam generation is transverse magnetic field induced phase dependent absorption between two Laguerre-Gaussian beams which connects two optical transitions of opposite polarities. We show how the coherent control field can be used to manipulate an azimuthal modulation of the absorption profile that is dictated by the phase and polarization structure of the probe beam. The mechanism of efficient generation and manipulation of an optical beam may have important applications in information science and optical communications.

Classical Isotope Effects in Precipitation and Recent Advancement

Date: 2016-11-29
Speaker: Mr. Harsh Oza
Venue: Ground Floor Lecture Hall

Abstract

The relationship between the oxygen and hydrogen isotopic composition (d18O and dD) of precipitation and certain climatic and geographical factors such as, surface air-temperature, amount of rain, altitude and latitude was well recognised and explained by the early 1960s. These have come to be known as classical isotope effects, namely, amount effect, altitude effect, continental effect, temperature effect etc. Over the years, with the advent of new scientific techniques, larger data sets from in-situ and remotely sensed observations and better understanding of climate systems some new concepts such as dependency of isotopes on types of cloud, atmospheric moisture residences time, late monsoonal depletion, local recycling, and western disturbances, etc. have also been recognized and explained. In this seminar some of the classical isotope effects will be revisited and recently reported newer observations will also be presented. Departure from the classical isotope effects observed in the Indian isotope dataset will also be pointed out along with possible explanation.

Biogeochemistry of trace elements in the seawater

Date: 2016-11-22
Speaker: Mr. Namandeep Singh
Venue: Ground Floor Lecture Hall

Abstract

Oceanic processes (physical, chemical and biological) set major controls on transport and transformation of mass and energy through different spheres of the Earth. Various trace elements present in the ocean waters are the integral part of these processes and are very sensitive to the processes involving their exchange and transport in the ocean. Many trace elements (e.g. Fe, Zn, Mn, Cu, Cd, Ni, Co) are nutrients to the marine primary producers. Consequently, these trace nutrients limit, in large parts of global ocean, the process of carbon and nitrogen fixation into organic matter, which directly regulates the atmospheric CO2 budget and hence the global climate. Trace elements (e.g. Mo, Cr, Pb, Ag) are also excellent tracers of Eh-pH conditions of the ocean waters and anthropogenic inputs to the oceans. A comprehensive study of biogeochemical cycling of these trace constituents is also therefore needed to understand marine ecosystem dynamics and the impact of human activities on it. In this presentation, I will discuss about biogeochemistry of some of the important trace elements involved in the oceanic processes with focus on bio-essential trace metal. Also, recent progress towards the understanding of biogeochemical cycling of some of these trace elements in the Indian Ocean and my near future research plans will be discussed.

Cosmic rays and global lightning activity

Date: 2016-11-21
Speaker: Dr. S. P. Gupta
Venue: Ground Floor Lecture Hall

Abstract

In May 1752, Benjamin Franklin has performed a famous kite experiment where he proved that lightning is an electrical phenomenon. This was a fundamental discovery and this was the beginning of atmospheric electricity research. More than 160 years later, another discovery was made by Victor Hess in August, 1912. He carried an electroscope and flew on board a balloon. He found that the rate of discharge of electroscope voltage decreases with altitude. Thus, he concluded that conductivity of air increases with altitude and the source of ionisation is somewhere in space. He called this source as “Kosmische Stralung” (a German word cosmic ray). Later Millikan coined the term cosmic rays. In recent years, a new source of ionisation in troposphere and stratosphere has been discovered. During thunderstorm activity and lightning activity, it is observed that gamma rays and high energy charged particles are emitted from the thundercloud. These high energy particles give rise ionisation in troposphere and stratosphere and, therefore, modulate the conductivity in these regions. These aspects will be discussed in this presentation.

What we have learned from 17^O-excess: a new tracer in hydrological cycle

Date: 2016-11-17
Speaker: Dr. Shyam Ranjan
Venue: Ground Floor Lecture Hall

Abstract

The stable isotope ratios of water in different phases acting as a powerful tracer of the global hydrological system. The ratio of 17^O/16^O and 18^O/16^O in air O2 and water is very useful for assessment for photosynthetic production on large scales as well as in the hydrologic cycle. For all these applications, the ratio of 17^O /16^O and 18^O/16^O in water should be known with very high precision. A new hydrological tracer: 17^O-excess can be used to estimate the past humidity changes from ice cores and trace the stratospheric water vapor intrusion (especially at a remote site in East Antarctica). Interestingly trace of stratospheric influence also has been recorded at the mid-latitude during large volcanic eruption i.e. Pinatubo eruption in 1991. Recent work on Western Himalaya (Indian Side) clearly indicates the influence of 17^O -excess during westerly and Indian Summer monsoon. The more in-depth study is needed to understand the role of 17^O-excess in Himalayan Glacier and its ecosystem.

Applications of Ultrafast Laser Writing and Photonic Nanojets

Date: 2016-11-17
Speaker: Dr. K L N Deepak
Venue: GF Lecture Hall

Abstract

Ultrafast laser direct writing is a technique with no parallel to deposit energy locally in short time scales to alter properties of materials (such as electrical, optical, and mechanical) without any damage to surroundings. The unique nonlinear interaction of light with matter due to high intensities associated with short pulses (of the order of femto-seconds) confines the modification within the focal volume of ultrafast light. Clear plastics (polymers) that are transparent exhibited fluorescence and para-magnetism upon interaction with a femtosecond laser. Bits of information can be encoded and stored in polymers by modifying locally with a femtosecond laser. 32 grey levels (5-bit) of information have been stored in a polymer Poly Methyl Methacrylate (PMMA) without any loss of information throughout the volume with a storage capacity up to 0.2 TB/disc. There have been attempts to overcome diffraction limited structures with standard ultrafast laser writing technique. Sphere assisted lithography (photonic nanojets) was shown to be promising to obtain not only diffraction limited structures but also micro-structuring over large surface areas with the help of mono-layers of spheres. Micro-structuring on a large surface area was demonstrated on different substrates including silicon, glass and quartz with dielectric spheres such as polystyrene and silica. Sphere assisted lithography/Photonic nanojet lithography technique was integrated with Laser Induced Forward Transfer (LIFT) technique to deposit 2D array of metal nanodots, and nano-triangles. By controlling the laser energy, metallic structures of different size, and shape were obtained. Ultrafast laser writing and photonic nanojets are promising for future applications in the areas of integrated photonics.

Atmospheric Methane from Agriculture in South Asia (AMASA)

Date: 2016-11-15
Speaker: Prof. Sachiko Amano Hayashida
Venue: Ground Floor Lecture Hall

Abstract

Methane (CH4) is the second most significant anthropogenic greenhouse gas. Most of methane emissions from Asia are attributable to ruminant animals and rice fields, but the quantitative estimate of methane emissions remains highly uncertain. Then we started a project to study methane emission estimate from South Asia. The project is supported by Ministry of Environment. The first goal of the project is to downscale the emission estimate from a global scale into a regional scale and improve methane emission estimate from South Asia by using GOSAT and ground-based data. To accomplish this goal, we are now collaborating with many local scientists and farmers to carry out in-situ measurements in India and Bangladesh. The second goal is to develop some emission mitigation proposals. In this project, we are focusing on methane emission from rice fields. One approach to reduce methane emission from rice fields is an intermittent draining of water, and another approach is a proper fertilizer management. Based on local experimental works on those measures, we will arrange some mitigation scenarios, and input them into an atmospheric transport model to examine if it is realizable or detectable.

Topological condensed matter physics wins Nobel

Date: 2016-11-10
Speaker: Navinder Singh and Namit Mahajan
Venue: Room No. 469

Abstract

David Thouless, Duncan Haldane and Michael Kosterlitz have won the 2016 Nobel Prize in Physics for their theoretical explanations of strange states of matter in two-dimensional materials, known as topological phases. The trio’s work in the 1970s and 1980s laid the foundations for predicting and explaining bizarre behaviours that experimentalists discovered at the surfaces of materials, and inside extremely thin layers. It is the Kosterlitz-Thouless phase transition, topological explanation of the quantum Hall effect, and the topological band theory that originates from the Haldane chains that form the basis for the Nobel prize. We will explain, in simple language, the physics behind these topics. In the end, we will also present brief biographical sketches of these great men of science.

Millimeter wave astronomy at the Institute of Applied Physics RAS: Instrumentation development and scientific results

Date: 2016-11-10
Speaker: Prof. Igor Zinchenko
Venue: Room - 113, Thaltej Campus

Abstract

In this review talk I will describe first the history and the current status of the developments of astronomical instrumentation at the Institute of Applied Physics of the Russian Academy of Sciences. They include low noise millimeter and submillimeter wave receivers, cryogenic systems for astronomy and other applications, precise laboratory spectroscopy, etc. In the second part I will present some results of our astronomical research, based mainly on millimeter and submillimeter observations of molecular spectral lines and dust continuum: surveys of high mass star forming regions, detailed investigations of several selected objects, observations of high-redshift objects, etc.

Structure and the chemical composition of the W40 dense core

Date: 2016-11-10
Speaker: Dr. L. E. Pirogov
Venue: Room - 113, Thaltej Campus

Abstract

The W40 dense core is associated with one of the nearest H~II regions and contains a clumpy dust ring probably formed by the ''collect and collapse'' process. Our observations revealed differences in physical characteristics of the clumps and the effects of chemical differentiation. The western clumps show chemical composition typical for evolved low-mass cores while the chemistry of the eastern clumps of the ring most probably is influenced by the closely located main HII region. The eastern clumps are more massive than the western ones, have higher degree of turbulence and indications of infall motions. The interaction between ionized gas and neutral material at the outer boundary of the eastern branch of the ring apparently triggers a new phase of star formation.

Orbital Angular Momentum (OAM) Mode Division Multiplexing in Optical Fibers

Date: 2016-11-04
Speaker: Dr. Pravin Vaity
Venue: G F Lecture Hall

Abstract

Internet data traffic is increasing exponentially with time and putting pressure on optical telecommunication networks whose backbone mainly consists of single mode fibers. To increase the data carrying capacity of single mode fibers, different multiplexing schemes as well as data formats have been proposed and demonstrated experimentally. These multiplexing schemes based on the properties of light which include wavelength, phase, amplitude and polarization. But these schemes are not enough for future capacity crunch, therefore, new multiplexing technique must be explored. To overcome this upcoming issue in communication systems, Orbital Angular Momentum (OAM) mode multiplexing has been proposed recently. OAM is an intrinsic property of light, which is quantized and allows infinite states of light unlike polarization. In this talk, I will discuss about OAM of light, design criteria for OAM supported fiber and data transmission study through it.

Hanle Resonances in Two Level Systems of Atomic Rubidium

Date: 2016-10-21
Speaker: Dr. Raghwinder Singh
Venue: G F Lecture Hall

Abstract

The effect of an additional transverse magnetic field (TMF) is studied on Hanle resonances for both linearly (σ) and elliptical polarized light in atomic Rubidium. The TMF redistributes the population among the Zeeman sublevels and its effect is found to be opposite for longitudinal and transverse magnetic field scans for elliptical polarized light. A new technique for measuring magnetic field using Hanle resonances with π-polarized light is reported with pure Rb vapor cells and a cell buffer gas. It is shown that with a π-polarized, no resonance signal is observed in absence of the TMF. When the TMF is applied, two dips are observed on either of zero scanning magnetic fields in the transmission spectrum. The separation between the two dips is linearly proportional to magnitude of the TMF, which can be used for magnetometry. The influence of a closed transition on neighboring open transitions that are partially resolved under Doppler broadening is also studied. We show that a sign reversal from an electromagnetically induced transparency (EIT) resonance to an electromagnetically induced absorption (EIA) resonance occurs with increase in ellipticity for the Fg = 2  Fe = 1 and Fg = 2  Fe = 2 transitions of 87Rb D2 line in a transverse field scan.

Breaking of longitudinal relativistic plasma waves and fourth order finite volume numerics for simulating accretion disks

Date: 2016-10-14
Speaker: Mr. Prabal Singh Verma
Venue: Room No. 469

Abstract

One of the major challenge in particle acceleration experiments is to achieve very high energetic charged particles. These high energetic particles are being used in cancer therapy, cutting and melting of hard materials and in understanding high energy physics problems. In conventional accelerators the accelerating electric field can not go beyond a few hundred MV/m due to the breakdown of the material. On the contrary, plasma which already is a broken state of matter can support extremely high electric field (TV/m) in the form of electrostatic plasma waves[2–9]. These waves can be excited as wakefields by sending a laser/particle beam pulse in to the plasma. Amplitude of such plasma waves is limited by a phenomenon called wavebreaking which transforms the coherent electrostatic energy of the wave into the random kinetic energy and thus damps the wave[1]. Therefore, understanding of wavebreaking criteria for plasma waves is important because it can significantly affect the maximum achievable energy in wakefield acceleration experiments. In the first part of my presentation I will talk about the the evolution and breaking of longitudinal relativistic plasma waves in a cold plasma [2]. In the second part, I will talk about the high order numerics for simulating accretion disks. Such disks are formed due the accumulation of matter on to a massive central object and the magnetorotational instability (MRI), which just requires a subthermal magnetic field to break the Keplerian flow into turbulence, is believed to be the most likely mechanism behind the accretion process. Most of the studies on the nonlinear development of the MRI rely on numerical simulations due to the inherent difficulties in approaching strongly nonlinear problems analytically. We have adopted shearing-box approximation [12] , where the computational domain is restricted to a region of small radial extent compared to its radial distance from the disk’s center, is a standard and well defined physical model to understand the nonlinear behaviour of the MRI. The existing numerical tools for MRI simulations are in general second order accurate and since second order schemes are known to have high numerical diffusion, we have developed fourth order accurate finite volume shock capturing code [13, 14] to study the nonlinear behaviour of magnetorotational instability (MRI). I will here talk about the issues we have encountered during the development of high precision code.

Novel method to deal off- shell particle in cascade decays

Date: 2016-09-30
Speaker: Mr. Tripurari Srivastava
Venue: Room No. 469

Abstract

I will discuss an algorithm to calculate decay width for cascade decay involving off-shell particles. First I will give you brief introduction to algorithm then I will explain and demonstrate it with some example with different kind of off- shell particles. Finally I will discuss some works still to be done in this context.

Rotation and Magnetism in Magnetohydrodynamics Simulations of Stellar Convection Zones

Date: 2016-09-30
Speaker: Dr. Bidya Binay Karak
Venue: Room - 113, Thaltej Campus

Abstract

It is believed that the magnetohydrodynamics processes are responsible for producing the solar magnetic field and the associated phenomena. Unfortunately, due to extreme conditions in the solar convection zone realistic direct numerical simulation of magnetohydrodynamics is not possible. However, significant progress can be made by performing simulations in local cartesian geometry and by producing turbulence using a forcing function. By choosing this forcing to be helical and by imposing a large-scale shear in the simulation box, we can easily excite large- and small-scale dynamos when the fluid is sufficiently random. I shall show that this kind of simple setup allows us to understand some basic questions of the solar magnetic field. Later, I shall present some results from rotating global-convection simulations in spherical geometry of the solar convection zone. I shall show that under certain parameter regimes, these solar-like global simulations are successful in reproducing a few basic features about the solar cycle. Features and origin of the differential rotation produced in these simulations will also be discussed.

Symbiotic novae from 1.2m eye

Date: 2016-09-22
Speaker: Dr. Vishal Joshi
Venue: Room - 113, Thaltej Campus

Abstract

Symbiotic novae is a rare subclass of novae in which secondary is a late type evolved star(instead of main sequence in case of classical novae). Unlike classical novae, such systems are not compact and material accrete onto white dwarf via secondary wind. Explosion of symbiotic novae are very interesting as ejecta interacts with circumbinary matter and shock forms. Such shock is thought to be to production site of X-rays and also Gamma-rays which are detected recently in very few novae. In this talk, I will mainly discuss recent results on symbiotic novae observed from MIRO 1.2m telescope.

Galaxy Formation and Evolution in the JWST/TMT Era

Date: 2016-09-15
Speaker: Dr. Nimish Hathi
Venue: Room - 114, Thaltej Campus

Abstract

A comprehensive analysis of star-forming galaxies (SFGs), including a crucial sub-population of Lyman alpha emitters (LAEs), at high redshifts (z~>2) using multi-wavelength photometry and deep spectroscopy is vital for understanding the physical processes that govern the star formation activity and galaxy assembly through cosmic time. Until now, such studies were limited to small number of galaxies because of the lack of large area, deep observations at high redshifts. With extensive multi-wavelength photometry from HST deep fields, and deep ground-based spectroscopy from ESO/VLT, we can now investigate physical properties of a large sample of SFGs/LAEs at z~>2. I will present results from recent photometric and spectroscopic studies of SFGs/LAEs at high redshift. These studies could lead to a more thorough investigation, over a much larger redshift range, using upcoming large telescopes such as JWST and TMT.

Revisiting the Pauli paramagnetism and the Landau diamagnetism in metals

Date: 2016-09-15
Speaker: Dr. Navinder Singh
Venue: Room No. 469

Abstract

In standard text books on statistical mechanics (Landau-Lifshitz, for example) the calculation of Pauli's paramagnetism is generally performed by neglecting the effect of magnetic field on density of states. However,the criterion of doing so was lacking so far. We work out the criterion of doing so, and thus give the calculation a rigorous foundation. Pauli's calculation is done by three different routes, and so provides a clear understanding. In the strong field limit (\mu_B H> k_B T) it is generally shown that total susceptibility shows de Haas van Alphen (dHvA) oscillations. We point out that even the Pauli paramagnetic susceptibity does show oscillations and a new formula equivalent to Lifshits-Kosevich is derived in terms of Fresnel integrals which goes to the original Pauli result once averaging over the oscillations is performed when low field limit is taken. A new formula in the intermediate temperature regime in terms of PolyLogs is also derived. The effect of electron scattering off bosonic modes on the Lifshits-Kosevich formula is also worked out.

Sources and Characteristics of Brown Carbon Aerosols over North India through Real-time Measurements

Date: 2016-09-12
Speaker: Mr. Satish R V.
Venue: Ground Floor Lecture Hall

Abstract

Recent studies have documented that a certain type of organic carbon (predominantly water soluble) significantly absorb light at near-UV (300-400) and visible regions, which is termed as “Brown Carbon (BrC)”. Recent global models estimate that light absorption by BrC in different regions of the world may be 30–70% of that due to black carbon (BC). To assess the role of BrC on regional and global level, it is important to understand their sources and characteristics on temporal and spatial scale, which is scarce in literature. Semi-continuous measurements of water soluble organic carbon (WSOC), BrC, BC and chemical composition of organic and inorganic aerosols were performed over Kanpur during winter season (December, 2015-Dec to February, 2016) using state-of-the-art instruments. Diurnal variability in the absorption coefficient of BrC at 365 nm (babs_365) showed higher values during late evening through early morning and attributed to primary emissions from biomass burning (BB) and fossil fuel burning (FFB). Primary BrC, assessed based on H:C ratios from HR-ToF-AMS, dominates the total BrC abundance with higher babs_365. Secondary BrC, assessed based on O:C ratios, was abundant in the morning and afternoon with lower babs_365. Further, diurnal variability in ratios of babs_365 with babs_405 and babs_420 suggests that BrC composition is not uniform throughout the day. Fog processing of BrC was also found to be affecting babs_365 positively.

Results from the Mars Science Laboratory rover

Date: 2016-09-08
Speaker: Dr. Jeremie Lasue
Venue: Room - 114, Thaltej Campus

Abstract

Since its landing in August 2012, the Mars Science Laboratory (Curiosity) rover has just completed two full martian years (approximately 4 terrestrial years) of exploring Gale Crater on the surface of Mars. As of October 2014, the rover started its goal to study layered sediments in the central mound of the crater. Before that, the mission drove and studied several areas on its way to the central Mound. Along the way, the rover observed evidence for past liquid water at the surface in the form of aqueously-altered minerals and sedimentary rock types indicative of transport in flowing water. In making these discoveries, the mission has already accomplished its overarching goal of finding evidence for past habitable environments on Mars. This talk will present highlights from the exploration, with particular emphasis on a tactical instrument on the rover called the ChemCam (Chemistry Camera) instrument. The result of collaboration between France and the United States, ChemCam includes an integrated remote Laser-Induced Breakdown Spectrometer (LIBS) and Remote Micro-Imager (RMI). The LIBS technique determines the elemental composition of a sample from the spectra emitted by a plasma of materials ablated by a high energy laser focused beam. The RMI is integrated into the telescope from which high resolution geological context images are recorded.

331 Models and Grand Unification: A Step From Minimal SU(5) to Minimal SU(6)

Date: 2016-09-01
Speaker: Mr. Chandan Hati

Abstract

We will discuss the possibility of grand unification of the 331 model.Two possibilities will arise.In SU(6) one can embed the 331 model as a subgroup such that different multiplets appear with different multiplicities.Such a scenario may emerge from the flux breaking of theunified group in an E(6) F-theory GUT.This provides new ways of achieving gauge coupling unification in 331 models while providing the radiative origin of neutrino masses.Alternatively, a sequential variant of the 331 model can fit within a minimal SU(6) grand unification, which in turn can be a natural E(6) subgroup. This minimal SU(6) embedding does not require any bulk exotics to account for the chiral families while allowing for a TeV scale 331 model with seesaw-type neutrino masses.

331 Models and Grand Unification: A Step From Minimal SU(5) to Minimal SU(6)

Date: 2016-09-01
Speaker: Mr. Chandan Hati
Venue: Room No. 469

Abstract

We will discuss the possibility of grand unification of the 331 model. Two possibilities will arise. In SU(6) one can embed the 331 model as a subgroup such that different multiplets appear with different multiplicities. Such a scenario may emerge from the flux breaking of the unified group in an E(6) F-theory GUT. This provides new ways of achieving gauge coupling unification in 331 models while providing the radiative origin of neutrino masses. Alternatively, a sequential variant of the 331 model can fit within a minimal SU(6) grand unification, which in turn can be a natural E(6) subgroup. This minimal SU(6) embedding does not require any bulk exotics to account for the chiral families while allowing for a TeV scale 331 model with seesaw-type neutrino masses.

What happened to the daytime 150-km echoing riddle?

Date: 2016-08-31
Speaker: Dr. A. K. Patra
Venue: Ground Floor Lecture Hall

Abstract

The daytime 150 km echoes were detected more than five decades ago using the Jicamarca radar, but their origin still remains elusive. Most of the 150 echoes, characterized by narrow spectral features (spectral width <15 m/s), were detected in the direction perpendicular to earth’s magnetic field and were believed to be due to field-aligned plasma irregularities generated by interchange instability. Subsequent measurements made by the Jicamarca radar in directions a few degrees away from perpendicularity displayed spectral width >1000 m/s and echo power 10-20 dB higher than that expected from incoherent scattering and were attributed to ‘naturally enhanced incoherent scattering’. Recent discovery of two distinct types of 150 km echoes, namely type-A and type-B, and subsequent progress in the large-scale kinetic simulation of photoelectron induced plasma waves have begun a new era in resolving the five decades long 150 km echoing riddle. More recent observations from Gadanki, which show unexpected behavior of these echoes, however, cannot be account for by the new theory. This talk is meant to discuss various observational facts gathered by various radars including the latest ones from Gadanki and the current thinking in resolving the 150-km echoing riddle.

Curvature perturbations from preheating

Date: 2016-08-24
Speaker: Dr. Arindam Mazumdar
Venue: Room No. 469

Abstract

Transition period between inflation and radiation domination is called reheating. Due to some problems with perturbative reheating a better version of reheating with non-perturbative mechanism was developed whichis known as preheating. Curvature perturbations generated during preheating has been calculated using lattice simulations and analytical formulations. But there had been no analytical approach available which could reproduce the results coming from the numerical simulations. I willpresent a framework for calculating super-horizon curvature perturbation from the dynamics of preheating, which gives a reasonable match to the lattice results. I will also discuss the problem of predicting non-gaussianity in this scenario.

Paleomonsoon reconstruction of Andaman Sea for the last ~66ka inferences based on the planktonic foraminifera

Date: 2016-08-23
Speaker: Mr. Kiran Kumar
Venue: Ground Floor Lecture Hall

Abstract

The Andaman Sea located in the northeastern region of the Indian Ocean, is very less studied and suitable region for studying the past monsoon variability based on the variation in the huge fresh water influx to Andaman Sea. This region is influenced by fresh water influx from the Irrawaddy and Salween river system, direct precipitation and the fresh water mixing from the Bay of Bengal through the surface current transport. The monsoon reconstruction based on the oxygen isotopic variation in the foraminiferal shells can be interpreted in terms of the variation in the paleo-fresh water influx from the river system. The relative difference of δ18O of different depth habitable species can be used as the freshwater induced upper ocean stratification. In this seminar I will discuss paleomonsoon reconstruction and the paleoceanography of Andaman Sea based on oxygen isotopic variation in the planktic foraminifera from the published data.

Throw the DICE for hints on Solar System formation

Date: 2016-08-19
Speaker: Dr. Bhalamurugan Sivaraman
Venue: GF Lecture Hall

Abstract

On the longitudinal variations in the daytime wave dynamics as seen in the optical dayglow emissions

Date: 2016-08-18
Speaker: Deepak Kumar Karan
Venue: Ground Floor Lecture Hall

Abstract

Equatorial dynamical processes in the upper atmosphere show both latitudinal and longitudinal variability as seen from results from several investigations that have been carried out by various research groups internationally. While the variability in latitudes is seen to exist in smaller distances, the longitudinal behaviour is shown over large spatial separations. In order to investigate the longitudinal differences over shorter separations, in the present work, we use optical dayglow emissions as tracers to the wave activity over different separations in azimuth. Systematic investigations on the spatio-temporal variations of optical dayglow emissions using a high resolution slit spectrograph called MISE, from a low latitude station Hyderabad have been carried out. MISE measures three optical dayglow emissions over a large field-of-view (FOV ~ 1400) at OI 557.7 nm, 630.0 nm, and 777.4 nm simultaneously, which emanate from three different altitudes, around 130, 230 and 300 km, respectively. We show that longitudinal differences in upper atmospheric processes can exist at even 3 degree separations. Spectral analyses of the waves that are separated in longitude, propagation characteristics of waves, and the diurnal emission pattern, do support our finding.

MFOSC-P - A Spectrometer-Camera for Mt. Abu 1.2m Telescope : The Optical Design

Date: 2016-08-18
Speaker: Dr. Mudit Srivastava
Venue: Room - 114, Thaltej Campus

Abstract

Mt. Abu Faint Object Spectrometer and Camera-Pathfinder (MFOSC-P) is envisioned as a general purpose user’s instrument providing both the imaging as well spectroscopy facilities within the same optical chain. The instrument is being designed as a pathfinder instrument for the FOSC on upcoming 2.5m PRL Telescope. Optics of the instrument has been designed for the visible wavelengths to provide spatial sampling of 3 pixels per arc-second of the seeing limited images. In spectroscopy mode two base resolutions of ~2000 and ~1000 using gratings/grisms would be provided. In the talk the speaker would discuss the details of optical design of the instrument as well as current status and future plans.

Using a novel spectroscopy technique for solving two long-standing mysteries in astronomy and astrophysics

Date: 2016-08-12
Speaker: Dr. Sunil Kumar
Venue: GF Lecture Hall

Abstract

In astronomy and astrophysics, there exist two several-decade-old mysterious spectra. One is referred to as the diffuse interstellar bands (DIBs) -- the absorption features that are observed in the visible to the near-infrared spectra of astronomical objects. The other is termed as the unidentified infrared emission bands (UIEs) -- the emission features observed in the mid-infrared spectra of the astronomical objects. Despite the observation of several hundred lines in the DIBs over nearly a century and several bands in the UIEs over four decades, only very few of them could be conclusively attributed to any known chemical species. At the Max Planck Institute for Nuclear Physics in Heidelberg, we are developing a novel spectroscopy technique with the objective to solving these mysterious spectra. In this technique, the molecular ions proposed to be the candidates for the spectral features in the DIBs and the UIEs (big carbon clusters such as fullerenes and polycyclic aromatic hydrocarbons) are stored in a cryogenic, electrostatic ion beam trap that simulates the true interstellar environment (with the temperature of 10 K and residual gas density of about 2000 particles/cm3). The stored molecular ions are then subjected to excitation by the laser light spanning the range (typically visible to near-infrared) of the absorption features of the molecular ion under concern. At resonance, the absorbed energy will be re-distributed among the vibrational modes of the molecule followed by the delayed emission of mid-infrared radiation from the triplet states. A fraction of the emitted light will be guided onto highly sensitive blocked impurity band (BIB) detectors which feature extremely low dark current and high sensitivity. Scanning the excitation laser wavelength provides the absorption spectrum (for the DIBs) and scanning the emitted infrared wavelength provides an emission spectrum (for the UIEs). The measurement scheme, preparatory work toward its implementation, and the current status of the experimental setup will be presented.

Photometric Studies on open star clusters

Date: 2016-08-11
Speaker: Dr. Devendra Bisht
Venue: Room - 114, Thaltej Campus

Abstract

Open clusters (OCLs) are excellent objects to investigate spiral arm structure, chemical composition, stellar population, dynamical evolution and star formation in the Galaxy. As we know, more than half of the currently catalogued open clusters (~3000) have been poorly studied or even not studied at all. Therefore, it is very essential to study the unexplored open star clusters to know the complete picture of the Galactic disk. This study includes the estimation of their physical parameters like radius, age, distance, reddening and metallicity. Here we present the broad band UBVI CCD photometry for several clusters using 104 cm Sampurnanand Telescope located at ARIES, Manora Peak, Nainital, India. The optical CCD data for these clusters are obtained for the first time. For open clusters Teutsch 126, Teutsch, 54, Teutsch 61 and Czernik 3 we hae used 2MASS JHKs data. The stellar density distributions and color-magnitude diagrams are used to determine their structural parameters (cluster center, cluster radius, core radius, tidal radius, Galactocenteric coordinates and the distance from the Galactic plane). We have estimated the age, distance, reddening, colour excess, total mass and dynamical relaxation time of these open star clusters as well.

Nitrogen cycling in terrestrial ecosystems

Date: 2016-08-09
Speaker: Ms.Â Niharika Sharma
Venue: Ground Floor Lecture Hall

Abstract

Nitrogen cycling in terrestrial ecosystems can play an important role in primary productivity and climate change. Study of gross N transformation rates can enable us to determine the capacity of plants to fix atmospheric carbon dioxide and hence the productivity in given set of climatic conditions. Also, emission of nitrous oxide (N2O) as an intermediate product of N-cycling is not fully understood and there remains lack of information regarding the balance in N2O budgets. In my talk, I would discuss these issues in detail and mention the application of stable isotopes in determination of each process. I would also discuss about different ecozones within India and rationale behind selecting such systems as my study areas.

Continuous transitions between quantum and classical systems

Date: 2016-08-04
Speaker: Prof. Partha Ghose
Venue: Room No:469

Abstract

The conventional demonstrations that classical mechanics is a limiting case of quantum mechanics are misleading. The purpose of the talk will be to offer a new equation which provides a continuous link between quantum and classical systems. Examples will be given to show these transitions in a few simple cases. New predictions can be made using this method for mesoscopic systems. *References*: P. Ghose, ``Continuous Transition Between Quantum and Classical Mechanics I'', Found. of Phys. vol 32, 871-892 (2002). P. Ghose and M. K. Samal, ``Continuous Transition Between Quantum and Classical Mechanics II'', Found. of Phys. vol 32, 893-906 ( 2002). W P Schleich, D M Greenberger, D H Kobe and M O Scully, ``A wave equation interpolating between classical and quantum mechanics'', Phys. Scr. vol 90,108009 (2015).

Can the jets showing bends or wiggles be relativistically beamed?

Date: 2016-08-04
Speaker: Prof. Ashok Singal
Venue: Room - 114, Thaltej Campus

Abstract

AGNs show relativistically moving jets, which many times show bends and wiggles on many scales. The conventional wisdom is that these jets appear very bright because they are oriented close to the line of sight of the observer and that relativistic beaming makes them look much brighter than they really are in their respective rest-frames. Now any misalignments seen in these jets would imply a change in the orientation angle, which should cause a large change in the beaming factor. But the bends and wiggles do not show such high contrasts. Is the appearances of such bends be really consistent with that the jets are relativistic? Are we missing something? In this talk I explore jets at different orientation angles with respect to the observer and thereby with different Doppler factors and investigate their effects on the intensities and appearances to the observer. It may be kept in mind that sometimes a small change in angle in the intrinsic frame might appear much larger due to the projection, more so when seen close to the line of sight. Therefore I take into account various projection effects in the jet appearance.

Reactive Oxygen Species (ROS) generation capacity of ambient aerosols over the Indo Gangetic Plain (IGP) during winter

Date: 2016-08-02
Speaker: Mr. Anil Patel
Venue: Ground Floor Lecture Hall

Abstract

Transition metals and other redox active species present in ambient aerosols have potential to produce Reactive Oxygen Species (ROS), which can severely impact the ambient air quality. ROS affect atmospheric chemistry, human health and agricultural productivity. However, studies on ROS generation capacity (i.e., oxidative potential (OP) or toxicity) of ambient aerosols are still lacking over India. The OP of aerosols, collected during winter from a site located in the Indo-Gangetic Plain, has been measured using Dithiothreitol (DTT) assay. Preliminary results suggest that the toxicity depends more on aerosol composition rather than its mass concentration. Relationship of OP with various chemical species has also been investigated. These results will be discussed in the present talk.

Journey of Binary Black Holes: From Supercomputer to LIGO to Universe

Date: 2016-07-29
Speaker: Mr. Karan Jani
Venue: Room - 114, Thaltej Campus

Abstract

The historic detections of binary black hole mergers in the first science run of Advanced LIGO has inaugurated the era of Gravitational Wave Astronomy. In this talk I recap the new astrophysics we have learned about black holes from these gravitational waves, and narrate our search plan to hunt for binary black holes as massive as 600 solar masses and up to cosmological distance of 10 Gpc. I emphasize the role of supercomputer simulations of solutions to Einstein Equations has played in confirming these gravitational wave signals as originating from black hole merger, and present a roadmap on how these simulations would guide future detections and hints of physics beyond General Relativity.

Fluorometric detection of dissolved Zinc in seawater

Date: 2016-07-26
Speaker: Mr. Venkatesh Chinni
Venue: Ground Floor Lecture Hall

Abstract

Low Zinc (Zn) concentrations in surface seawater could limit growth of phytoplankton which in turn may limit primary production” – Zinc Hypothesis. Although like Iron (Fe), this hypothesis has not been verified in open oceans through field studies, but cultural experiments show growth of microorganism’s (more than 300) is limited by the low concentrations of Zinc. Also, in the oceans, dissolved Zinc (DZn) has a nutrient like vertical profile with a particularly strong correlation with silicate. Checking the Zinc hypothesis (Whether it can limit primary production or not) and understanding its relation with silicon is the contemporary area of interest for many chemical and biological oceanographers. To understand these things one should have a better knowledge on the biogeochemical cycle of Zn which is poorly understood due to the sparse observations in the world Oceans especially in the Indian Ocean. Measuring Zn concentrations in the ocean is highly challenging due to its presence of sub nanomolar levels, high matrix and its ubiquitous nature of contaminating the samples. In this talk, I will discuss about the sensitive flow injection method which has been established in the lab for the determination of sub nanomolar levels of DZn in seawater using fluorometric detection. Further, the new results on DZn obtained in the North-Eastern Indian Ocean and associated Zinc biogeochemistry will be presented.

Quantum aspects of self-accelerating non-dispersive wave packets

Date: 2016-07-22
Speaker: Dr. Vivek M Vyas
Venue: GF Lecture Hall

Abstract

It is well known that classically a particle can not accelerate in absence of an applied force. Surprisingly, in 1979, Berry and Balazs found that the free particle Schrodinger equation admits a wave packet solution that linearly accelerates and is non-dispersive. Several different explanations have been offered to understand unusual behavior of such wave packets, which provide valuable insights into working of quantum mechanics. In this talk, we shall review some of these explanations, and shall discuss some of our recent work in this area.

Unveiling the nature of Infrared-Faint Radio Sources (IFRSs)

Date: 2016-07-21
Speaker: Dr. Veeresh Singh
Venue: Room - 114, Thaltej Campus

Abstract

Recent deep radio surveys combined with auxiliary InfraRed (IR) surveys have discovered a new population called ‘Infrared-Faint Radio Sources’ (IFRSs) that are relatively bright radio sources with faint or no counterparts in IR and optical wavelengths. Given the dearth of more sensitive optical and IR data, the initial investigations on IFRSs were limited to radio wavelengths. We identify and investigate the nature of IFRSs in deep extragalactic fields, wherein deep optical (m_r ~ 25; Subaru, Very Large Telescope), near-IR (m_K ~ 23; UKIDSS, VIDEO), mid-IR ([3.6] ~ 2 microJy, Spitzer) data are available, along with the deep radio data. Our results suggest that IFRSs population constitute primarily radio-loud Active Galactic Nuclei (AGN) at higher redshifts (z ~ 1.7 - 4.0). In general, IFRSs exhibit compact radio emission with steeper radio spectra and thus suggesting them to be young radio galaxies in their early phase of evolution. Given the faintness or non-detection of IFRSs in optical/IR/X-ray wavelengths, it is plausible that IFRSs represent the population of obscured AGN as postulated by the modelling of X-ray extragalactic background emission.

A geochemical approach to the history of sedimentation in the Neoproterozoic Marwar Basin, Rajasthan

Date: 2016-07-19
Speaker: Mr. Bivin Geo George
Venue: Ground Floor Lecture Hall

Abstract

The Late Neoproterozoic to Early Cambrian (750Ma- 500Ma) witnessed remarkable events in the Earth’s history such as the break-up of the supercontinent Rodinia and amalgamation of Gondwanaland, evolution of multi-cellular life, a major oxygenation event and the evolution of a climate system that is similar to the present day. These global events often leave their imprints in the contemporaneous sedimentary rocks. In the talk, I shall discuss our ongoing efforts in unravelling some of these mysteries through geochemical studies of the sediments deposited in the Neoproterozoic Marwar basin of Rajasthan. Results of our study aimed at constraining the age, understanding the provenance, paleogeography and tectonic setting of the basin shall be presented in the talk.

Urban Heat Islands and Air Conditioning

Date: 2016-07-18
Speaker: R. N. Misra
Venue: Ground Floor Lecture Hall

Abstract

Overall rise in average temperature of the cities in the past two decades, has accelerated use of air-conditioning of office and living spaces. The installations have been a retrofit procedure in most of the locations, resulting in extensive changes in external appearance of buildings, which are now dotted by air-conditioners all around, either window type or split type .The heat removed from inside space is discharged into the environment in the form of hot air blown from the fan cooled heat exchanger . This results in hot air blast emanating from the windows all around, which in turn, causes increase of temperature of the surroundings and accelerates formation of urban heat island (UHI). An attempt has been made to broadly analyze the scenario and suggest changes in the air-conditioning technology, to reduce the impact on the environment.

Sub Poissonian Statistics of Heralded Single Photons generated from Spontaneous Parametric Down Conversion

Date: 2016-07-15
Speaker: Mr. Nijil Lal C. K
Venue: GF Lecture Hall

Abstract

The developments in the field of Quantum Information science require successful candidates for quantum bits (qubits). Quantum states of a single photon are ideal qubit candidates. Spontaneous Parametric Down-Conversion (SPDC) is an important non-linear process in which heralded single photons are generated. Photons can exhibit different probability distributions based on the nature of the source. Classical sources like thermal/partially coherent light show super-Poissonian statistics and coherent light show Poissonian statistics, while single photon sources are characterized by the non-classical sub-Poissonian statistics. In this talk, I will discuss about the statistics of both classical and non-classical sources of light on the basis of photon number fluctuations. Also, I will discuss the sub-Poissonian statistics of Type-I SPDC photons and hence the confirmation of their non-classical nature.

Cooling and heating mechanism in cool-core cluster galaxies: A case study of ZwCl 2701

Date: 2016-07-15
Speaker: Dr. Nilkanth Vagshette
Venue: Room - 114, Thaltej Campus

Abstract

Observational evidences of cooling and heating mechanism are now available in majority of galaxy clusters. Heating from Active Galactic Nuclei (AGNs) is considered to be the prime candidate to offset/quench the cooling flow. We performed a systematic search for such heating mechanism (cavities/bubbles) in hot gas of galaxy clusters (specifically in ZwCl 2701) by using Chandra archival data. These observations of ZwCl 2701 show the presence of an extensive pair of ellipsoidal cavities along the East and West directions within the central region of <20 kpc. Detection of bright rims around the cavities suggested that the radio lobes displaced X-ray emitting hot gas forming shell-like structures. Comparable values of cavity power and cooling luminosity of ZwCl 2701 suggested that the mechanical power of the AGN outburst is large enough to balance the radiative cooling in the system. The star formation rate derived from the H_alpha luminosity was found to be 0.60 M_sun/yr, which is about three orders of magnitude lower than the cooling rate of ~ 196 M_sun/yr. The details will be discussed in the seminar.

Life at high salt concentrations: Sulfate reduction and survival mechanisms

Date: 2016-07-12
Speaker: Prof. Alakendra N. Roychoudhury
Venue: Ground Florr Lecture Hall

Abstract

Coherence and Dicke super-radiance

Date: 2016-07-08
Speaker: Dr. Vivek M Vyas
Venue: GF Lecture Hall

Abstract

Half a century back, Dicke studied a model of a collection of two level atoms interacting with a single cavity mode. It was found that when the atoms are in what is called Dicke state, the photon emission probability is significantly larger than the spontaneous emission probability, which was called super-radiance. In this talk, it will be shown that such a super-radiant state of photons is actually a coherent state. The relation between Bose-Einstein condensation, spontaneous symmetry breaking and super-radiance in photonic systems will be shown. It will be shown that super-radiant emission of photons from Dicke states is fundamentally different from spontaneous and stimulated emission phenomena.

A study of the static and dynamical thermal conductivity of metals and other systems

Date: 2016-07-07
Speaker: Mr. Pradeep Kumar
Venue: Room No:469

Abstract

The Mori?s projection method, known as memory function method is an important theoretical formalism to study various transport coefficients.In the present work, we calculate the dynamical thermal conductivity in the case of metals using the memory function formalism. We introduce thermal memory functions for the first time and discuss the behavior of thermal conductivity in both zero frequency limit and in the case of non-zero frequencies. We compare our results for the zero frequency case with the results obtained by the Bloch-Boltzmann kinetic approach and find that both approaches agree with each other. Motivated by some recent experimental advancements, we obtain several new results for the ac or the dynamical thermal conductivity.

Effect of equatorial electrodynamics on optical neutral dayglow emissions

Date: 2016-06-27
Speaker: Deepak Kumar Karan
Venue: Ground Floor Lecture Hall

Abstract

Equatorial electrodynamical processes are quite intriguing and their manifestations in the low latitudes are varied. Both ionospheric and thermospheric measurements are used to understand the various modes of coupling between the neutrals and the plasmas. We have carried out systematic investigations on the variations in the optical dayglow emission intensities from a low latitude station Hyderabad, using a high resolution slit spectrograph, called MISE, which enables simultaneous measurements of dayglow emissions at OI 557.7 nm, 630.0 nm, and 777.4 nm over large field of view. These emissions that originate from different altitudes have been used to obtain neutral wave characteristics in the recent past. With respect to the diurnal behaviour in dayglow intensities, a solar zenith angle dependence (symmetric with respect to local noon) is expected as the production mechanisms are photochemical in nature. However, deviations from such solar zenith angle dependence (asymmetric with respect to local noon) have been observed. Detailed investigations on the neutral and electrodynamical parameters have been carried out to explain these deviations in the diurnal behaviour of emission intensities. It is found that the equatorial electrodynamics has a significant role to play in governing these deviations. Further, on the days when asymmetric behaviour in dayglow emissions are seen, longitudinal differences in the equatorial electrodynamical processes are found to exist. This is in contrast to the days when the diurnal behaviour is symmetric. These spatio-temporal differences in the daytime airglow emission intensities and their dependence on the equatorial electrodynamics will be presented.

Seesaw mechanism of Neutrino mass generation and some TeV scale variants : A review

Date: 2016-06-24
Speaker: Mr. K. Vishnudath
Venue: Room No:469

Abstract

In spite of their weakly interacting nature, we have so far accumulated an enormous amount of knowledge about neutrinos. From neutrino oscillation experiments, we learned a few years ago that neutrinos are massive and flavours are mixed. However, we still do not know the absolute values of their masses. Seesaw mechanism is considered to be one of the most natural approach toward understanding the sub-eV neutrino mass scale. In my talk,I will review the seesaw mechanism of neutrino mass generation and some of its proposed TeV scale variants, including seesaw mechanisms in Left-Right symmetric models.

Looking for T-violation in B decays

Date: 2016-06-23
Speaker: Ms. Bharti Kindra
Venue: Room No:469

Abstract

Since the discovery of CP violation in neutral K, and B meson system, experiments have questioned the existence of T violating effects as well.In 2012, direct time reversal violation was observed for the first time at asymmetric B factory PEP-II where an entangled B-Bbar state is produced.CP and flavour specific final states are employed to identify the initial state quantum numbers and properties, which are then used to study the T-conjugated processes. Non zero results showed that T is indeed violated independent of Cp violation. In my talk, I will discuss the experiment and the phenomenology used therein, and describe some work that is being done in this direction.

Properties of high mass X-ray binary pulsars

Date: 2016-06-23
Speaker: Gaurava K. Jaisawal
Venue: Room - 114, Thaltej Campus

Abstract

The accretion powered X-ray pulsars are rotating neutron stars that powered in X-rays as a result of mass accretion from the optical companion. They are consider to be ideal astrophysical laboratory to test the fundamental properties of matter under extreme conditions. During the process of accretion, the interaction between pulsar's magnetic field and accreting gas results in the formation of a column like structure on the poles of neutron star that acts as the source of X-ray emissions. The accretion column has complicated geometry, hosting numerous complex processes that shape the broad-band continuum of these objects. In this talk, I will discuss about these mechanisms, emission beam patterns, properties of pulse profiles and observational evidences to directly estimate and probe the magnetic field of these pulsars.

An evidence for prompt electric field disturbance driven by changes in the solar wind density under northward IMF Bz condition

Date: 2016-06-20
Speaker: Diptiranjan Rout
Venue: Ground Floor Lecture Hall

Abstract

The effects of prompt penetration electric fields are generally observed over equatorial ionosphere during southward turning of interplanetary magnetic field (IMF Bz), northward turning of IMF Bz (after a steady southward condition) and also during the transient geomagnetic disturbances like substorm and storm sudden commencement. In one of our recent study, it is shown that three different types of prompt electric field disturbances, occurring in succession over a period of 6 hours, have affected the equatorial ionosphere-thermosphere system on a single night. These electric fields are shown to be associated with pseudobreak-up/substorm, prompt penetration due to southward turning of IMF Bz and also DP2 type processes. However, the effects of solar wind density in generating the prompt penetration electric field have not been investigated so far. The evidence in this regard is obtained recently. In this present talk, the effects of the solar wind density in causing prompt penetration electric field under northward IMF Bz condition will be presented.

Advances in Optical Sectioning and Optical Manipulation of Biological Samples

Date: 2016-06-17
Speaker: Dr. Manoj V. Mathew
Venue: GF Lecture Hall

Abstract

In this talk I will discuss some of the advances in using light especially lasers for imaging biological samples in three dimensions and manipulating them. The gold standard in high-resolution imaging is confocal microscopy that primarily uses linear fluorescence. Non-Linear optics has also found its way into exploring the biological world. Tools like multiphoton fluorescence and Second Harmonic Generation (SHG) are being increasingly used to image biological samples and extract finer details. Newer approaches are also using light sheets for faster and deeper imaging of whole organisms and thick tissues. Precise focusing and nonlinear confinement of NIR ultrafast laser light is being used for precise nano-surgical interventions.

Hot flux ropes observed by SDO

Date: 2016-06-16
Speaker: Aparna V. Sastry
Venue: USO Seminar Hall

Abstract

Decade long optical monitoring of blazar 3C66A

Date: 2016-06-16
Speaker: Mr.Sameer
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Blazars are radio loud AGNs with their relativistic jets pointed close to line of sight of the observer boosting their emission due to relativistic beaming. They show rapid and strong variability spanning the entire electromagnetic spectrum, high and variable polarization in radio and optical regimes and dominant non-thermal emission from radio to high energy gamma-rays. These also show long term variations with varying time scales. It would be interesting to see if the short term variations have any relationship with the long term trends. Keeping this in mind, we have been monitoring a set of blazars from Mt Abu IR Observatory (MIRO) for more than 10 years now. In this presentation, I would like to discuss this program, with specific study of BL Lac Object 3C66A. The monitoring of blazar 3C66A, from 2005 November to 2016 February, in the B, V, R, I broad bands using 1.2m telescope of MIRO was carried. Blazar 3C66A exhibited significant variations in optical flux on short and long term time scales. However, it showed a IDV duty cycle of about 16% only. Our statistical study, using structure function, discrete correlation functions and L-S periodogram suggests time scales of intra- night variability from ~ 30 min to about 3.5 hours, and, in at least one case existence of quasi-perodic oscillations with a period of ~ 2.5 hr. The IDV amplitudes in R-band were found to vary from 0.02 mag to as high as 1.1 mag. The typical rate of flux variation was estimated to be ~0.06 mag/hr in both the rising and falling phases. The shortest timescale of variation results in setting an upper limit of 8.1 x 10^14 cm for emitting region size and about 4.3 x 10^8 Msun as mass of black hole.

Holocene Monsoon variability using stalagmite records from Dandak and Kotumsar caves, India.

Date: 2016-06-14
Speaker: Ms. Shraddha Band
Venue: Ground Floor Lecture Hall

Abstract

Variability and trends in the Indian Summer Monsoon (ISM) during mid-Holocene time period has remained a debatable issue. While some proxy based records show changes to be a gradual process in response to decreasing solar insolation, there are postulates of abrupt decline at 6 ka as well. We have attempted to address this long standing controversy using a highly resolved ISM reconstruction, based on delta-18-O measurements (n = 5040) on stalagmite samples, from Dandak and Kotumsar caves from the Core Monsoon Zone of India. Results will be discussed in the seminar.

Water in the Universe: From Clouds to Ocean

Date: 2016-06-03
Speaker: Kinsuk Acharyya
Venue: Room 113 (Thaltej campus)

Abstract

Water in the Universe: From Clouds to Ocean

Date: 2016-06-03
Speaker: Kinsuk Acharyya
Venue: Room #114 (Thaltej campus)

Abstract

Planet Formation in Dense Star Clusters

Date: 2016-06-02
Speaker: Dr. Henry Throop
Venue: Seminar Room - 113 (Thaltej Campus)

Abstract

Our Solar System's closest stellar neighbors are several light years away, and most models of the Solar System's formation assume that we have been isolated from other stars. But a growing body of evidence suggests that most stars and planets form in star clusters far more dense, where tens of thousands of young stars are initially packed into the same volume of space as between us and our closest stellar neighbors. The Orion region is one such nearby dense stellar cluster, where UV radiation, clouds of gas, and encounters with other stars can shape the future of planetary systems. I will discuss our recent observations and modeling of the formation of stars, disks, and planets in dense star clusters such as Orion, and what this says about the formation of stars and planets throughout the galaxy.

1. INVESTIGATION OF DUST DISTRIBUTION SURROUNDING A PLANET, 2.DESIGN OF IMPACT IONIZATION DUST DETECTOR AND DERIVATION

Date: 2016-05-27
Speaker: 1. Pinali J. Bhalodi, 2. Darshil K. Patel
Venue: Room 113 (Thaltej campus)

Abstract

Speaker: 1. Pinali J. Bhalodi (M.E. Trainee) Title : INVESTIGATION OF DUST DISTRIBUTION SURROUNDING A PLANET Speaker: 2. Darshil K. Patel (M.E. Trainee) Title : DESIGN OF IMPACT IONIZATION DUST DETECTOR AND DERIVATION OF SOURCE INFORMATION

INVESTIGATION OF DUST DISTRIBUTION SURROUNDING A PLANET, DESIGN OF IMPACT IONIZATION DUST DETECTOR AND DERIVATION OF SOURCE INFORMATION

Date: 2016-05-27
Speaker: Pinali J. Bhalodi, Darshil K. Patel
Venue: Room #114 (Thaltej campus)

Abstract

Soft X-Ray Telescope onboard ASTROSAT and Study of Blazars

Date: 2016-05-23
Speaker: Dr. Sunil Chandra
Venue: Seminar Room-113 (Thaltej Campus)

Abstract

Soft X-ray telescope (SXT) is a focusing X-ray telescope onboard the first Indian space-based multi-wavelength observatory ASTROSAT. The focusing optics of SXT, approximate Wolter-I type configuration, is capable to enable us X-ray imaging in 0.3-8.0 keV band. The focal plane camera is very similar to the one flown with Swift XRT. The SXT along with other instruments onboard ASTROSAT namely, UVIT, LAXPC and CZTI, becomes a very unique astronomical facility which can simultaneously cover a very broad energy range (130-530 nm & 0.3-150 keV) of spectrum. Since its launch on 28 September 2015, the instruments onboard ASTROSAT are producing very exciting results for a variety of astronomical sources for example AGNs, XRBs, Clusters etc. Blazars, because of their emission ranging over almost complete spectrum, are one of the key sources for ASTROSAT science. The simultaneous observations of emission produced because of two different processes (Synchrotron and SSC ) will enable us to improve the basic understanding of processes in these objects. In this talk I will present few preliminary results obtained from the SXT observations.

A silicon isotopic approach to constrain the building block of Earth

Date: 2016-05-20
Speaker: Jinia Sikdar
Venue: Room 113 (Thaltej campus)

Abstract

What is the Earth made up of? This is one of the most fundamental yet highly debatable aspects of planetary sciences. Although it is known from quite a very long time that the Earth accreted from some sort of primitive material delivered as meteorites but the exact nature of such meteorites have not been determined so far. As such, a number of Earth forming models requiring accretion of a random mixture of different varieties of meteorites have been proposed from time to time. In this talk, I will discuss how our high precision Si and Mg isotopic measurements have helped us in constraining the type of meteorites that contributed a major fraction in Earth?s accretion. This has implications towards the estimation of bulk Earth composition by which we can evaluate the conditions of core-mantle differentiation followed by a revised estimation of the amount of light elements that might have been incorporated into Earth?s core.

A silicon isotopic approach to constrain the building

Date: 2016-05-20
Speaker: Jinia Sikdar
Venue: Room #114 (Thaltej campus)

Abstract

Design and Development of LEAPS payload

Date: 2016-05-17
Speaker: Dr. Damayanti Gharpure
Venue: Room #114 (Thaltej campus)

Abstract

What we learn about Vesta from Piplia kalan and Lohawat meteorites

Date: 2016-05-13
Speaker: M.S. Sisodia
Venue: Room 113 (Thaltej campus)

Abstract

What we learn about Vesta from Piplia kalan and Lohawat meteorites

Date: 2016-05-13
Speaker: M.S. Sisodia
Venue: Room #114 (Thaltej campus)

Abstract

Vanishing act of 142Nd anomaly: story of the Khariar alkaline rocks

Date: 2016-05-10
Speaker: Ms. Ikshu Gautam
Venue: Ground Floor Lecture Hall

Abstract

Understanding of the early differentiation of the silicate earth requires knowledge of 142Nd isotope composition in various terrestrial reservoirs. Produced by decay of short lived 146Sm (t1/2 = 68 Ma) the radiogenic 142Nd is expected in primordial materials or subsequent products that may still carry its memory. Because of extremely low abundance of 146Sm, measurement of radiogenic 142Nd is very cumbersome and the anomalies (if any) in its isotopic ratios are expected in the six decimal place. Every anomalous value reported for 142Nd w.r.t. terrestrial standard is therefore very important and affects the understanding of these early differentiation processes. In this context, the negative anomalous values reported for 1.48Ga alkaline rocks from Khariar are particularly important. These anomalous values have been questioned and reported to be analytical artefacts. We have carried out an independent study of these rocks and studied in detail the data acquisition and reduction methods to understand its effect on data quality control. I will discuss the parameters that can bias the data and the results of our experiment.

CeBr3 Scintillator for Gamma-Ray Spectrometer

Date: 2016-05-06
Speaker: Dipak Kumar Panda
Venue: Room 113 (Thaltej campus)

Abstract

CeBr3 Scintillator for Gamma-Ray Spectrometer

Date: 2016-05-06
Speaker: Dipak Kumar Panda
Venue: Room #114 (Thaltej campus)

Abstract

Quantum information with even/odd states of orbital angular momentum of light

Date: 2016-05-06
Speaker: Mr. Chithrabhanu P
Venue: G F Lecture Hall

Abstract

Orbital angular momentum (OAM) of light beams has been recently explored for the implementation of many quantum information tasks. This is an infinite dimensional degree of freedom which can be used along with polarization. However, for many protocols we just need to have two dimensional qubits of OAM. Experimentally this was done by restricting the detection to two OAM states, which causes huge loss of photons. Instead, we address the possibility of using even/odd states of OAM of photons for the quantum information tasks so that the photon number will be preserved. We consider single photon qubit states as well as two photon entangled states in even/odd basis of OAM. We present a method for the tomography and general projective measurement in even/odd basis. With the general projective measurement, we can have the Bell violation which can be used in quantum cryptography. I will describe schemes for the various measurements and implementation of quantum protocols such as super dense coding and teleportation.

Study of Evolution of Magnetic Inhomogeneities on The Sun Using Narrow Band Imaging

Date: 2016-05-04
Speaker: Mr. Sajal Kumar Dhara
Venue: USO Seminar Hall

Abstract

Surface active substances in atmospheric aerosol.

Date: 2016-05-03
Speaker: Mr. A. K. Sudheer
Venue: Ground Floor Lecture Hall

Abstract

Surface active substances (surfactants) are significant part of soluble organic content of atmospheric aerosol. They reduce the surface tension of water droplet and influence the cloud droplet formation and have potential role precipitation process, but, their abundances and extent of surface tension reduction is not well understood. In this talk, indirect methods for measurement surface active substances in atmospheric aerosol and implication will be discussed.

Surface active substances in atmospheric aerosol.

Date: 2016-05-03
Speaker: Mr. A. K. Sudheer
Venue: Ground Floor Lecture Hall

Abstract

Surface plasmon resonance based interferometric techniques for nanophotonic applications

Date: 2016-05-03
Speaker: Dr. Mahua Bera
Venue: Room 113, Thaltej Campus

Abstract

Surface plasmons are free charge oscillations occur at the interface of metal and dielectric layer. Surface plasmon resonance (SPR) based phase measurement technique provides higher accuracy than conventional intensity measurement techniques. In this talk I will discuss some of our recent results on SPR based radially sheared interference imaging and novel scheme of incoherent and coherent Moiré pattern generation and their possible applications in switching, logic operations and non-contact testing of surface profilometry.

Are there quantum limits to transport in quantum many-body systems?

Date: 2016-04-28
Speaker: Dr. Nandan Pakhira
Venue: Room No. 469

Abstract

ABSTRACT --------------- Good metals like copper and gold are characterised by diffusive transport of coherent quasi-particle states. The electrical resistivity (ρ)which characterises charge transport in these materials is well within the Mott-Ioffe-Regel (MIR) limit, ha/e2(where a is the lattice constant) i. e. (ρ << milli-Ω cm). Also the shear viscosity (η) which characterises momentum transport is also bounded, i. e., η << nħ/5(where n is the density of electrons) in the quasi-particle regime of transport. But in a wide range of strongly correlated materials and most notably in the strange metal regime of doped cuprates (high-Tc superconductors) the resistivity exceeds the MIR limit and the picture of coherent quasi-particle based transport breaks down. Recently, a holographic duality (AdS/CFT correspondence) based approach in string theory led to a proposed universal lower bound η/s ≥ħ/4π kB for the ratio between the shear viscosity (η) and the entropy density (s). This bound is found to be valid in a wide class of classical fluids like water and quantum fluids including the quark-gluon plasma in the Relativistic Heavy Ion Collider (RHIC) and cold atomic fermionic gases in the unitary limit of scattering. Also, loosely motivated by holographic duality, and inspired by the quantum bound to η/s Hartnoll proposed a lower bound to the charge diffusion constant D ≥ ħvF2/kB T the incoherent regime of transport [2], where vF is the Fermi velocity and T the temperature. Using dynamical mean field theory (DMFT) we calculate the diffusion constant and shear viscosity in the single band Hubbard model. We explore possible violation of Hartnoll's proposed bound [3] and possible existence of quantum bounds in the shear viscosity (η) entropy density (s) ratio in the incoherent regime of transport [4].

The Origin and Evolution of Water on Mars: Insights from Martian Meteorites

Date: 2016-04-28
Speaker: Dr. Meenakshi Wadhwa
Venue: Room 113 (Thaltej campus)

Abstract

The Origin and Evolution of Water on Mars: Insights from Martian Meteorites

Date: 2016-04-28
Speaker: Meenakshi Wadhwa
Venue: Room #114 (Thaltej campus)

Abstract

Magnetic Field in High Mass X-ray Binaries

Date: 2016-04-28
Speaker: Mr. Prahlad Epili
Venue: Seminar Room -113 (Thaltej Campus)

Abstract

X-ray Binaries (XRBs) are the astrophysical systems powered by accretion onto a compact object which gravitationally captures part of the mass lost by its companion star. Many of the observed properties of XRBs depend upon the mass of the companion star, which classifies the XRBs as high mass X-ray binaries (HMXBs) and low mass X-ray binaries (LMXBs). Among the HMXBs, the largest population are Be/X-ray binaries consisting of NSs with Be type companions. The accretion in these systems is mainly quasi-spherical wind/ disk accretion. During the episodes of giant outbursts, the pulse period in these systems show significant spin-up. Recently in October 2013, KS 1947+300 (a Be/X-ray binary) gone through a giant outburst with peak luminosity reaching ~1038 erg s-1 (with a mass accretion rate ~ 1018 g/s). It showed a significant spin-up in the NS pulse period. We have used its spin-up rate to estimate the magnetic field of the pulsar by using the theory of settling quasi-spherical accretion. The details of pulse-period variations and evolution of X-ray pulse profiles of KS 1947+300 during the giant outburst with subsequent changes in the spectral parameters over the pulse phase will be discussed.

Magnetic Field in High Mass X-ray Binaries

Date: 2016-04-28
Speaker: Prahlad Epili
Venue: Room - 114, Thaltej Campus

Abstract

Gamma Ray Spectrometer for future Mars mission: Design concept and simulation study

Date: 2016-04-22
Speaker: Shiv Kumar Goyal
Venue: Room 113 (Thaltej campus)

Abstract

Gamma Ray Spectrometer for future Mars mission: Design concept and simulation study

Date: 2016-04-22
Speaker: Shiv Kumar Goyal
Venue: Room #114 (Thaltej campus)

Abstract

Characteristics of Aerosols: Observations and Model Simulations

Date: 2016-04-18
Speaker: S. Ramachandran
Venue: Ground Floor Lecture Hall

Abstract

Aerosols continue to contribute the largest uncertainty to the total radiative forcing estimate owing to the limited knowledge that we possess on the processes that control the aerosol distributions, wide diversity in their sources, physical, chemical and optical properties accompanied with significant spatiotemporal variations. A wide range of aerosol characteristics and their size distributions are being measured now by several ground-based networks and space-borne instruments in addition to intensive field campaigns in different regions across the globe. However, in order to obtain a complete picture of optical, physical and chemical properties of aerosols, both ground-based and satellite measurements are necessary and should be combined with global models of aerosols. Furthermore, the aerosol models developed on the basis of microphysical processes of formation and removal of different aerosol species need to be evaluated with full range of aerosol observations. Despite the importance the studies on climate model simulations and comparison with ground-based measurements and satellite data on regional and global scales are rather sparse. The seminar will focus on the results obtained from an analyses of aerosol characteristics measured using sun photometers, satellites (Moderate Resolution Imaging Spectroradiometer (MODIS) and Multiangle Imaging SpectroRadiometer (MISR), and simulated by global aerosol models (Global Ozone Chemistry Aerosol Radiation and Transport (GOCART) and Model for Ozone and Related Tracers (MOZART)) over different locations/regions.

Mechanical Design and Analysis of New APXS Package On-board Chandrayaan 2

Date: 2016-04-15
Speaker: Balaji Viswanathan
Venue: Room 113 (Thaltej campus)

Abstract

Mechanical Design and Analysis of New APXS Package On-board Chandrayaan 2

Date: 2016-04-15
Speaker: Balaji Viswanathan
Venue: Room #114 (Thaltej campus)

Abstract

Post LGM sedimentation record in marine marginal basin of the Great Rann of Kachchh, Western India

Date: 2016-04-12
Speaker: Dr.Niteshkumar N Khonde
Venue: Ground Floor Lecture Hall

Abstract

The enigmatic terrain of the Great Rann of Kachchh (GRK) basin is bounded by Thar Desert; Aravalli ranges in the north and northeast, whereas its southern and western boundary is shared with Kachchh mainland hills and Arabian Sea respectively. Situated on continental margin of Indian subcontinent, the GRK basin has preserved continuous record of post glacial sedimentation that continued till recent past. Structurally a half graben, the GRK has witnessed complex interplay of climate-tectonic forcing throughout the Quaternary times. Several scientific issues regarding GRK basin yet to understand completely such as- the provenance of the sediments, geomorphic evolution, land-sea interaction changes, marine inundation pattern and its role in flourishing the earlier civilization invites earth scientists to reconstruct its past. To address some of these issues, the preliminary results from GRK studies provide evidences of tectonic upliftment, land-sea interaction and paleoclimatic/paleo-environmental changes throughout post LGM would be discussed.

Student Project Presentations

Date: 2016-04-08
Speaker: S.Sekhar Naik - IIST, Anvesh Bogavelly - IIST, Rohit Singh - IIST, Vimmi Chokhawala - DDU
Venue: Room 113 (Thaltej campus)

Abstract

Student Project Presentations

Date: 2016-04-08
Speaker: S.Sekhar Naik , Anvesh Bogavelly, Rohit Singh, Vimmi Chokhawala
Venue: Room #114 (Thaltej campus)

Abstract

Role of waves and small-scale transients in the heating of solar atmosphere

Date: 2016-04-07
Speaker: Dr. Girjesh R. Gupta
Venue: Room-114, Thaltej Campus

Abstract

The tenuous outer atmosphere of the Sun commonly known as 'corona', is orders of magnitude hotter than the solar surface. Heating of the solar corona along with acceleration of solar wind remain two of the most puzzling problems in the solar and space physics. There are several theories proposed to explain the phenomena, however, to identify any one dominant process is extremely difficult to do. Magnetohydrodynamics (MHD) waves and magnetic reconnection resulting in to transient release of energy, are currently the most promising heating models. In this presentation, speaker will mainly discuss different wave modes possible in the solar corona and their observational signatures. Some recent observational examples of propagation, and damping of MHD waves in the solar atmosphere will be presented. Contribution of energy carried by these waves in the context of heating of solar corona and acceleration of solar wind will also be discussed. Few examples of small-scale transient energy release events due to magnetic reconnection and their importance in the heating of solar atmosphere will also be presented.

Zircons are forever

Date: 2016-04-05
Speaker: Prof. J. S. Ray
Venue: Ground Floor Lecture Hall

Abstract

Zircon (ZrSiO4) is an omnipresent trace mineral in most silicate rocks present on the surface of the earth. Because of its refractory nature and ability to concentrate uranium and exclude lead it has been widely used as a U-Pb geochronometer for igneous rocks from the very beginning of the Solar System (in meteorites) to the Present. The only physical evidence from the earliest phases of Earth’s evolution comes from zircons. Oxygen isotope ratios from such zircons have been used to infer about the nature of the earliest hydrosphere and its habitability for life. There are countless usefulness of zircons in studies in Earth and Planetary Sciences. In my talk I would highlight some of these and make a case for zircon research for Indian Geology.

LPSC 2016: A few highlights and presentation on Martian dust study

Date: 2016-04-01
Speaker: J P PABARI
Venue: Room #114 (Thaltej campus)

Abstract

LPSC 2016: A few highlights and presentation on Martian dust study

Date: 2016-04-01
Speaker: Jayesh P Pabari
Venue: Room 113 (Thaltej campus)

Abstract

Strong Hemisperic Asymmetry can Trigger Parity Changes in the Sunspot Cycle

Date: 2016-03-31
Speaker: Dr. Soumitra Hazra
Venue: Room-114, Thaltej Campus

Abstract

Although sunspots have been systematically observed on the Sun's surface over the last four centuries, their magnetic properties have been revealed and documented only since the early 1900s. Sunspots typically appear in pairs of opposite magnetic polarity which have a systematic orientation. This polarity orientation is opposite across the equator -- a trend that has persisted over the last century since observations of sunspot magnetic fields exist. Taken together with the configuration of the global poloidal field of the Sun -- that governs the heliospheric open flux and cosmic ray flux at Earth -- this phenomena is consistent with the dipolar parity state of an underlying magnetohydrodynamic dynamo mechanism. Although, hemispheric asymmetry in the emergence of sunspots is observed in the Sun, a parity shift has never been observed. We simulate hemispheric asymmetry through introduction of random fluctuations in a computational dynamo model of the solar cycle and demonstrate that changes in parity are indeed possible over long time-scales. In particular, we find that a parity shift in the underlying nature of the sunspot cycle is more likely to occur when sunspot activity dominates in any one hemisphere for a time which is significantly longer compared to the sunspot cycle period. Our simulations suggest that the sunspot cycle may have resided in quadrupolar parity states in the distant past, and provides a possible pathway for predicting parity flips in the future.

Top FCNC decays in the aligned two-Higgs doublet model

Date: 2016-03-29
Speaker: Dr. Gauhar Abbas
Venue: Room No. 469

Abstract

We compute the flavour-changing top decays t -> ch and t -> cV (V =g ,Z)within the framework of the aligned two-Higgs-doublet models. By exploiting constraints fromflavour physics and themeasured Higgs properties, we investigate the parameter space of the modeland its impact on theassociated branching ratios. It is observed that the Higgs signal strengthin the di-photon channelimposes important restrictions on the t -> ch decay rate when the chargedscalar of the model islight. We conclude that the rates of these flavour-changing top decays are beyond the expected sensitivity of the future high-luminosity phase of the LHC.

Paleoredox and paleo-pH conditions in Earthly Environments: Implications and Application of Calcium Isotopes

Date: 2016-03-29
Speaker: Mr. Wriju Chowdhary
Venue: Ground Floor Lecture Hall

Abstract

To reconstruct oxygenation and pH history of the Earth's surface environment through time and its affect on the evolution of life on our planet, it is essential to know about paleoredox and paleo-pH conditions. Modern analogs and lab simulations have mostly provided a good understanding about the processes responsible for the isotopic and chemical trends. Paleoredox and paleo-pH conditions characteristic of the water column from which precipitates have formed are recorded in REE and trace elemental concentrations and calcium isotopic variations of the lithified records respectively. In this seminar, I plan to discuss how the REE and trace elemental concentrations have been used to decipher paleoredox proxies and concentrate on a proposal to use calcium isotopes as an indirect proxy of paleo-pH. This study has implications for the improvement of predictive power to the understand the processes driving isotope fractionation during changing paleo-environmental conditions through multiproxy approach.

Tentative detection of Chlorine on Rhea

Date: 2016-03-18
Speaker: Bhalamurugan Sivaraman
Venue: Room 113 (Thaltej campus)

Abstract

Bhalamurugan Sivaraman

Date: 2016-03-18
Speaker: Bhalamurugan Sivaraman
Venue: Room #114 (Thaltej campus)

Abstract

A multi-wavelength study of star formation activity in the S235 complex

Date: 2016-03-17
Speaker: Dr. Lokesh Dewangan
Venue: Room-114, Thaltej Campus

Abstract

The energetics of massive stars (M > 8 Msun) can strongly influence the surroundings. Massive stars can destroy star-forming clouds (i.e., negative feedback) and can also trigger star formation (i.e., positive feedback), leading to the formation of a new generation of stars including young massive star(s). In this talk, I will present results of a multi-wavelength analysis of a nearby massive star-forming S235 complex, helping to understand the feedback of a massive (O-type) star. The S235 complex has a sphere-like shell appearance at wavelengths longer than 2 micron and harbors an O9.5V type star. The position-velocity analysis of CO reveals an almost semi-ring like structure, suggesting an expanding HII region. The CO and dust continuum emissions trace eight embedded subregions, and five of them appear to be distributed in an almost regularly spaced manner along the sphere-like shell surrounding the ionized emission. We find that the dust clump masses increase as we move away from the location of the ionizing star. Photometric analysis reveals the clusters of young sources that are very well correlated with the dust clumps and CO gas. Together, all these results are interpreted as observational evidence of positive feedback of a massive star.

Planet Hunting & The Heritage of PARAS

Date: 2016-03-11
Speaker: Ms. Arpita Roy
Venue: Room-114, Thaltej Campus

Abstract

Twenty years ago, astronomers discovered the first exoplanet around a Sun-like star. Since then, we have become prolific exoplanet hunters and the field of radial velocity exoplanet detection has made tremendous strides towards ever-increasing precision. Pushing into extreme levels of precision (~10cm/s), we are now on the brink of discovering true Earth analogs, which will redefine our understanding of planetary habitability, and present the first realistic targets for discovering non-terrestrial life in the Universe. Highly stabilised, high-resolution, efficient spectrographs with adequate telescope allotments are required for this unique high-reward science goal. I will review the current state of the field for RV studies, and the value of instruments like PRL's PARAS spectrograph in the global effort to find and characterise exoplanets. Further, PARAS provides critical heritage and lessons for the next generation of precision instruments like the Habitable Zone Planet Finder (HPF, currently being assembled) and the NASA Extreme Precision Doppler Spectrograph (EPDS, in competition for award), both of which I am working on at Penn State. The current performance of PARAS promises great utility in the near future, as a workhorse spectrograph for they follow-up of TESS and PLATO candidates. In concert with HPF and EPDS, PARAS will play a powerful role in defining targets for future direct detection missions like JWST and HabEx.

Understanding the Luminous Supernovae and the role of small-size telescopes

Date: 2016-03-10
Speaker: Dr. Rupak Roy
Venue: Room-114, Thaltej Campus

Abstract

This is now established that the life of every massive star ends through a violent explosion, know as Core-Collapse Supernova (CCSN). In last couple of decades both theories and observational skills had been developed to understand the diversities of the CCSNe along with their origins and after-effects. In the most common scenario the core of such a star collapses under self-gravity and forms a compact object, while the outer shells are thrown away in the form of a cosmic catastrophic event. After the year 2005, dedicated surveys like CRTS, LOSS, ROTSE, PTF, PanSTARRS have discovered several events which have an average absolute Visual-band peak magnitude of about -21 mag, more than 2 mag brighter than CCSNe. These are Superluminous SNe (SLSNe). It seems that SLSNe are neither occurring in the nearby universe, nor are they hosted in massive-galaxies like our Milky Way. The mechanism for SLSNe is still not well understood. The circumstellar interaction or emergence of a magnetar after core-collapse or disruption of a massive star through pair production are the proposed scenarios. It is also not clear whether by origin the progenitors of CCSNe and SLSNe are same or are they different ? Recent research revealed that there are few events which come in between these two classes. These gap-transients are important to constrain the nature of the progenitors of these two different populations as well as their environments and explosion mechanisms. Here, we will discuss about the impact of circumstellar interaction on the observed properties of luminous supernovae and the importance of such study to understand the massive stars in the near and far universe. We will also discuss about the probability to detect such objects at early phases from the ground and space-based observatories and the role of small-size telescopes in this regard.

Efficient nonlinear generation of high power, higher order, ultrafast 'perfect' vortices in green

Date: 2016-03-04
Speaker: Mr. Apurv Chaitanya
Venue: G F Lecture Hall

Abstract

Recent developments in the field of structured beams have led to a new class of optical beams known as 'perfect' vortices. Unlike normal optical vortices, the perfect vortices have ring radius independent of its topological charge (order). Such property makes perfect vortices interesting for many fields in science and technology. In this talk I will discuss on our recent work on nonlinear generation of "perfect" vortices. Based on Fourier transformation of the higher order Bessel-Gauss beam generated through the combination of spiral phase plate and axicon we have transformed the Gaussian beam into perfect vortices of power 4.4 W and order up to 6. Using single-pass second harmonic generation (SHG) of such vortices we have generated perfect vortices at green wavelength (530 nm) with output power of 1.2 W and vortex order up to 12 at single-pass conversion efficiency of 27%, independent of the orders. This is the highest single pass SHG efficiency of any optical beams other than Gaussian beams.

ISRO-NASA Mars Data Analysis Group Meeting Brief and Project Presentations

Date: 2016-03-04
Speaker: Vijayan S. , Rishitosh K. Sinha
Venue: Room #114 (Thaltej campus)

Abstract

Neutrino Mass Models at the LHC

Date: 2016-02-25
Speaker: Prof. Frank Deppisch
Venue: Room No. 469

Abstract

Models of neutrino mass generation provide well motivated scenarios of Beyond-the-Standard-Model physics. The synergy between low energy and high energy LHC searches facilitates an effective approach to rule out,constrain or ideally pinpoint such models. In my seminar, I will provide a brief overview of scenarios where searches at the LHC can help determine the mechanism of light neutrino masses and potentially falsify baryogenesis mechanisms.

Exploring novel quantum phenomena in photonic settings: From fundamentals to technological applications

Date: 2016-02-25
Speaker: Dr Somnath Ghosh
Venue: G F Lecture Hall

Abstract

Corroborating the analogy between non-Hermitian quantum system and counterpart optical geometries with suitable amount of simultaneous gain and loss, I plan to discuss an innovative scheme for asymmetric mode conversion in a coupled optical system under certain condition in the strong coupling regime (beyond the PT symmetry limit) exploiting singularities (in eigen values and eigen vectors) associated with avoided crossings (in the regime where adiabatic evolution fails) as an efficient tool. Novel propagation dynamics of light wave through this special optical structure is evident, which is being explored in the context of optical isolation for integrated/ on-chip photonics applications. From fundamental physics point of view and applications in photonics like realizing compact random lasing in one dimensional disordered system (longitudinal direction mapped onto time), I plan to focus on my latest findings to demonstrate that the simultaneous presence of spatial and refractive index disorder favors Anderson localization of light. This study has revealed several underlying interesting features of light confinement to a localized state in such a medium of finite length and showed that beyond the point of localization, light indeed propagates without any diffractive spread in the transverse direction in a disordered lattice, a feature that mimics waveguide-like propagation. The hallmark stochastic nature of the phenomena has been encountered in both simulations and experiments using ultrafast laser inscription (ULI) technique.

Subsurface Exploration of Mars using Shallow Radar (SHARAD) on board Mars Reconnaissance Orbiter

Date: 2016-02-19
Speaker: Rajiv Ranjan Bharti
Venue: Room 113 (Thaltej campus)

Abstract

Subsurface Exploration of Mars using Shallow Radar (SHARAD) on board Mars Reconnaissance Orbiter

Date: 2016-02-19
Speaker: Rajiv Ranjan Bharti
Venue: Room #114 (Thaltej campus)

Abstract

Looking at Ultraluminous X-ray sources and Cataclysmic Variables through the hard X-ray window using NuSTAR

Date: 2016-02-18
Speaker: Dr. Vikram Rana
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

The Nuclear Spectroscopic Telescope Array (NuSTAR) is the first mission to carry focusing high-energy X-ray telescope in space. NuSTAR, with its unprecedented combination of sensitivity, spatial and spectral resolution, turned out to be an ideal observatory to probe the hard X-ray properties of Ultraluminous X-ray sources (ULXs) and Cataclysmic Variables (CVs) as well as other X-ray binaries. ULXs are of prime interest, as they may be associated with a poorly explained regime of super-Eddington accretion onto a stellar mass black hole (BH), or even contain sub-Eddington intermediate mass BHs. Broad-band X-ray study of a sample of bright ULXs with XMM-Newton and NuSTAR revealed that all the sources in the sample show a clear cutoff at or above ~10 keV, strongly suggesting different physical origin for their X-ray emission compared to Galactic black hole X-ray binaries and supporting exotic super-Eddington modes of accretion. CVs, on the other hand, contain an accreting white dwarf as a compact object. NuSTAR provided a first direct detection of reflection component in three magnetic CVs, namely, V709 Cas, Ny Lup and V1223 Sgr. In the past, there was only an indirect evidence for the existence of reflection component based on presence of Fe fluorescence line. NuSTAR observations provided an important piece of information required to obtain a complete picture of these magnetic CVs. During this talk, I will discuss recent interesting science results on ULXs and CVs using hard X-ray data from NuSTAR and simultaneous soft X-ray coverage with XMM-Newton and/or Suzaku.

Monojet constraints for the 750 GeV diphoton resonance

Date: 2016-02-16
Speaker: Dr. Suchita Kulkarni
Venue: Room No. 469

Abstract

The recent announcement of a mild excess in diphoton channel around 750 GeV has generated a lot of excitement. I will exemplify phenomenology a simplified model containing a scalar resonance coupling to gluon, photon and dark matter particle. I will describe constraints due to existing dark matter monojet searches on this parameter space. If the resonance is confirmed in the next round of data taking, the simplified model considered here will be either ruled out or lead to insights into the scale of new physics.

Latest developments in space weather forecast by means of ground- based facilities

Date: 2016-02-15
Speaker: Prof. Robertus Erdelyi and Team
Venue: USO Seminar Hall

Abstract

Evolution of models proposed for jet emission in blazars

Date: 2016-02-11
Speaker: Ms. Navpreet Kaur
Venue: Seminar Room # 113/114 (Thaltej Campus)

Abstract

Blazars, a sub-class of AGN (Active Galactic Nuclei), are known to show featureless spectra due to jet dominated emission owing to the peculiar orientation of jet axis towards us. They prove to be the most violent and highly energetic sources in the Universe because of greatly amplified intrinsic effect by relativistic boosting. Understanding their energetics and emission processes has been a challenge for astrophysicists and attempts were made to constrain the jet physics based on observational light curves. With advancement in observational technology and the establishment of multi-wavelength campaigns, it became difficult to explain the observations by those earlier existing models. In the talk, I would like to briefly summarize the evolution of blazar jet models proposed to explain physical processes and structure along with some of our observations.

NSSS 2016 Oral Presentation speakers (8 minutes each)

Date: 2016-02-05
Speaker: NSSS 2016 Oral Presentation speakers

Abstract

1. Shanmugam M 2. Ramakant R Mahajan 3. Dwijesh Ray 4. Poornima KV 5. Vijayan S. 6. Rishitosh K. Sinha

Moving with the Comet - Science Results Update from Rosetta

Date: 2016-02-04
Speaker: Mr. Kumar Venkataramani
Venue: Room # 006 (Thaltej Campus)

Abstract

It has been a long journey for the International Rosetta Mission, from getting the approval in November 1993 to May 2014, when the spacecraft first reached the comet 67P/ Churyumov?Gerasimenko and to November 2014, when philae made a soft landing on the comet, the first ever of its kind. All through, it has been sending back wonderful data and high resolution images. Apart from missions like Stardust, Deep Impact and many other flyby's, for the first time ever, the comet's nucleus was imaged with high resolution cameras like OSIRIS on board the space-craft and the nuclear surface was probed directly by the lander. More recently, VIRTIS spectrometer on board the spacecraft has confirmed detections of water ice on the nucleus of the Comet. There are many more such interesting results coming from the so called Europe's comet chaser. These results can be a guiding step even for our ground based observations of various other comets. I would like to briefly discuss and summarize some of them in the talk.

Space Weather research in HVAR Observatory

Date: 2016-02-02
Speaker: Mateja Dumbovic
Venue: USO Seminar Hall

Abstract

Title: Evolution of Zanskar Valley (Ladakh Himalaya) since Permian

Date: 2016-02-02
Speaker: Dr. Anil Dutt Shukla
Venue: Ground Floor Lecture Hall

Abstract

Zanskar valley in Ladakh Himalaya provides a rich repository of the pre and post collision history which is preserved in the sedimentary sequences spanning a time period ranging from Proterozoic to Eocene. The sedimentary formations belonging to the Tethyan Sedimentary Sequence (TSS) are present in the Zanskar valley which represents the frontal part of large-scale southwest-verging imbricated structures. It has been suggested that the TSS were deposited in the passive continental margin and the lithology provides an entire spectrum of geological history of the Tethyan Ocean ranging from Late Carboniferous to Permian rifting of Gondwana (NeoTethys) till the collision of the India with Asian continent around Eocene. The outpouring of Panjal traps occurred during the opening up of the Neo-Tethyes and is ascribed to the rifting during the Permian. This was followed by near continuous sedimentation which is represented by Triassic to late cretaceous sedimentary facies (arenaceous, argillaceous and bioclastic sediments) in gradually subsiding Tethyan basin till the Eocene when Indian plate sutured with the Asian plate. In this presentation, I would discuss about the current understand of the Zanskar basin with emphasis on the geochemistry of the Panjal volcanic, it implications (if any) in the P-T extinction and subsequent sedimentation till the Indian-Eurasian collision.

Quasi-biennial oscillation modulation of semidiurnal tides

Date: 2016-02-01
Speaker: Fazlul I. Laskar
Venue: Ground Floor Lecture Hall

Abstract

Semidiurnal (12-hour) tides are one of the dominant motions in the mid- and high-latitude mesosphere-lower-thermosphere region of the atmosphere. Investigations are carried out on the behavior of semidiurnal tides using specular meteor radar based horizontal wind measurements from northern mid- and high-latitude stations, Juliusruh (54N, 13E) and Andenes (69N, 16E). It is observed that the amplitudes of semidiurnal tides in the mesospheric altitude show systematic variability with that of low-latitude stratospheric quasi-biennial oscillation. These observations and their interpretations will be presented along with broad understanding of the background.

Interstellar Dusts and their Laboratory Analog

Date: 2016-01-29
Speaker: Kinsuk Acharyya
Venue: Room #006 (Thaltej campus)

Abstract

Mercury monohalides: promising new candidates for search of the electron electric dipole moment

Date: 2016-01-29
Speaker: Srinivasa Prasannaa
Venue: Room No. 469

Abstract

Heavy polar diatomic molecules are the primary tools for searching for the P and T-violating electric dipole moment of the electron (eEDM). Valence electrons in some molecules experience extremely large effective electric fields, which are crucial to the success of polar-molecule-based eEDM search experiments. In this talk, we report on the results of relativistic ab initio calculations (using the relativistic coupled cluster method) of the effective electric fields in a series of molecules that are highly sensitive to an eEDM, the mercury monohalides (HgF, HgCl, HgBr,and HgI). We identify HgBr and HgI as attractive candidates for future electric dipole moment search experiments. We also discuss why these molecules have such large effective electric fields.

Astrochemistry @ 2015: A Review and where we stand?

Date: 2016-01-29
Speaker: Dr. Balamurugan Sivaraman
Venue: G F Lecture Hall

Abstract

Astrosat CZTI: Pre-flight calibration to in-flight operation

Date: 2016-01-28
Speaker: Mr. Mithun Neelkandan
Venue: Room # 006 (Thaltej Campus)

Abstract

Astrosat, India's first observatory class mission for multi-wavelength Astronomy was launched on 28th September 2015. Cadmium Zinc Telluride Imager (CZTI) is one among the five instruments on-board Astrosat. The instrument is composed of a large array of pixelated CZT detectors. Equipped with coded aperture mask it is capable of imaging and spectroscopy in 20-150 keV energy range. In this talk, I will present the details of ground calibration, response modeling and in-flight performance of the instrument. Some preliminary results from CZTI will also be discussed.

A Lorentz covariant local theory of fermions with mass dimension one

Date: 2016-01-21
Speaker: Prof. Dharam Vir Ahluwalia
Venue: Room No. 469

Abstract

In this informal seminar I will construct eigenspinors of the charge conjugation operator for spin one half and show that they do not satisfy Dirac equation. This has been known for about a decade now. The new result that I'll present is on constructing a mass dimension one fermionic field. Reference: http://arxiv.org/pdf/1601.03188

Very Low Mass stars and Exoplanets

Date: 2016-01-21
Speaker: Dr. Arvind Singh Rajpurohit
Venue: Room # 006 (Thaltej Campus)

Abstract

Very Low-Mass stars (M dwarfs) are an important source of information for probing the low mass end of the main sequence, down to the hydrogen burning limit. They are the dominant stellar component of the Galaxy. Moreover, an increasing number of M dwarfs are now known to host exoplanets, including super-Earth exoplanets. The determination of the accurate fundamental parameters for M dwarfs has therefore relevant implications for both stellar and Galactic astronomy as well as planetology. In this talk I will focus on spectroscopic approach using updated model atmosphere with the aim of obtaining their precise parameters. Further, I will discuss about the recent advances in both observations and theory of Hot-Jupiter atmospheres.

Solar Polarimetry

Date: 2016-01-20
Speaker: Sankarasubramanian
Venue: USO Seminar Hall

Abstract

Presentations on Plan Proposals -- Rehearsal

Date: 2016-01-15
Speaker: Amit Basu Sarbadhikari , Shiv K. Goyal , Vinai K. Rai
Venue: Room #006 (Thaltej campus)

Abstract

Time evolution of clusters and molecules

Date: 2016-01-12
Speaker: Dr. Koushik Saha
Venue: G F Lecture Hall

Abstract

Stable clusters and molecules under effect of external perturbation attain excited states. This excited system relaxes via various mechanisms at different timescales after perturbation. By studying the time evolution of such excited systems, different types of relaxation mechanisms involved in the de-excitation process can be probed as a function of time, thus, yielding vital information about the underlying dynamics involved. In this talk, I will present the experimental studies that we have performed to understand the time evolution of excited cluster anions and also briefly discuss about the methodology to study the time evolution of excited molecules.

Ultra-high peak electric field THz pulse generation via high intensity femtosecond laser-plasma interaction

Date: 2016-01-12
Speaker: Dr. Sudipta Mondal
Venue: G F Lecture Hall

Abstract

When a high power laser pulse from a multi-terawatt (1012 Watt) laser system is focused on a solid surface, a special type of plasma is formed on the solid surface, a high temperature and high density plasma with very steep density gradient. The state of the matter which is created here is comparable to the inner material of a stellar object. Information about these high intensity femtosecond laser plasma interactions is required in inertial fusion research, laboratory astrophysics and many other purposes. High intensity short pulse laser plasma interaction also produces highly energetic short bunches of charged particles (electrons, protons and ions). Next generation of particle accelerators are predicted to be based on laser plasma interaction. They also produce high energetic electromagnetic pulses such as high-order harmonics, soft and hard x-rays. Recently we found high intensity laser plasma interaction also generates GHz and THz pulses with high energy per pulse. Intense broadband THz pulses are opening new scientific areas to explore, such as nonlinear optics in the THz domain, as well as single-shot THz spectroscopy and imaging. Intense THz pulses can also be used to develop THz streak cameras, which could measure the temporal characteristics of femtosecond X-ray and electron bunches generated by methods such as high-intensity femtosecond laser-plasma interaction. This technique of THz pulse generation can be a potential source of ultra-broadband and intense THz light pulses. Particle-in-cell (PIC) simulations have predicted that GV/cm THz fields can be generated by such laser-plasma interactions. An attractive advantage of this method is that unlike other conventional THz sources (such as the optical rectification technique), there are no known limits in the maximum laser intensity that could be used to drive these laser-plasma THz sources. Therefore, these methods could potentially be driven at very high laser intensities, giving rise to even higher THz yield. In this presentation I’ll mainly focus on a part of my postdoctoral research which is intense THz pulse generation via high intensity femtosecond laser plasma interaction which I have developed at INRS-EMT. Generated THz pulses are characterized and then pulse energy is optimized by controlling plasma conditions and interaction process. These THz pulses can be used as novel probe for laser plasma interaction process. Our recent research covering this prospect will also be discussed.

Top Physics in the LHC Era

Date: 2016-01-12
Speaker: Dr. Pankaj Sharma
Venue: Room No. 469

Abstract

The ultimate goal of the Large Hadron Collider (LHC) is to reveal the secrets of electroweak symmetry breaking (EWSB) and discover the new physics beyond the Standard Model (SM) of particle physics. The top quark has been believed to be a key to uncover the veil over EWSB and new physics. The top quark is unique in the sense that it decays before it can form a bound state and thus allows a possibility to measure its polarization. In this seminar, I will discuss various ways to measure the top quark polarization and its usefulness in constraining various new physics models at the LHC. I will also discuss how the top quark can be utilized to characterize the properties of the newly discovered Higgs boson at the LHC. Also, excesses have been seen in the charged-Higgs boson searches at CMS at around 250 GeV and 500 GeV massese in the 13 TeV data which point to a very fat charged Higgs. I will also discuss how this can be explained in the purview of type-II 2HDM.

The axial U(1) anomaly and topological structures in finite temperature QCD

Date: 2016-01-11
Speaker: Dr. Sayantan Sharma
Venue: Room No. 469

Abstract

The magnitude of axial U(1) symmetry breaking is believed to affect nature of Nf = 2 QCD chiral phase transition. The explicit breaking of chiral symmetry due to realistic light quark masses is small hence it is important to use fermions which do not break chiral symmetry on the lattice, to understand the fate of axial U(1) near the chiral crossover temperature, Tc. I discuss on our recent study of the eigenvalue spectrum of QCD with two different lattice fermion discretizations which retain a remnant of the continuum chiral symmetry. Studying the eigenvalue spectrum we do not observe any hints of the effective restoration of axial U(1) near Tc. A pile up of the near-zero eigenmodes is observed to persist even at 1.5Tc which are primarily responsible for its breaking. These eigenmodes are localized unlike those in the bulk, with a mobility edge similar to a Mott-Anderson like system. The origin of such near-zero mode spectrum can be traced back to the dilute instanton gas ensemble already setting in at 1.5 Tc. Our study for the first time also investigates in great detail the topological structures in QCD just near the chiral crossover transition from the data for topological susceptibility. I also discuss the consequences of our results for topological susceptibility in QCD for the prediction of the amount of axion dark matter.

Consequences of f(R) gravity in Randall?Sundrum Model

Date: 2016-01-08
Speaker: Dr. Sampurnanad Jha
Venue: Room No. 469

Abstract

One of the vexing issues of the standard model of particle physics is to explain the disparity between the Planck scale and the electroweak scale. An interesting approach due to Randall Sundrum (RS), does explain the discrepancy by assuming a 4+1 dimensional world. In this model, extra dimension is compactified on a circle whose upper half is identified with the lower half and the known world is confined to one of a pair of three-branes that sit atop the two fixed points. However, the value of the compactification radius is treated as a model parameter and not determined by the dynamics of the model. Such a degree of freedom violates the equivalence principle. We point out that the corrections to the gravity sector of the Einsein-Hilbert action can lead to scalar degree of freedom which, interacting with the radius field (modulus), results in an effective potential for it. The effective potential thus obtained is minimized to set a value of compactification radius. We show that for reasonable values of model parameters, the hierarchy between the Planck scale and the electroweak scale can be explained in a modulus stabilized scenario. Further, we also discuss that the scalar field, that arises naturally in our model, can be used to explain the magnetic field present on cosmological scale.

From quantum transport to non-equilibrium dynamics: quantum simulations with ultracold atoms

Date: 2016-01-08
Speaker: Dr. Bodhaditya Santra
Venue: G F Lecture Hall

Abstract

Predicting the dynamics of an interacting many-body system is often a challenging task either by an analytical method or by numerical simulation. The way to a faster and more accurate solution was embedded in the vision of Feynman?s quantum computers for universal quantum simulations. Ultracold quantum gases offer unique possibilities to simulate quantum dynamics in a highly controllable and precisely tunable setup. In this talk I will present two examples where we have investigated the quantum dynamics of a Bose-Einstein condensate loaded in a 1D optical lattice. In the first experiment we observe Negative differential conductivity, which is a widely exploited mechanism in many areas of research dealing with particle and energy transport. In the second experiment we investigate the non-equilibrium steady-states (NESS) of a driven-dissipative superfluid. NESS constitute fix points of the phase space dynamics of classical and quantum systems. They emerge under the presence of a driving force and lie at the heart of transport phenomena such as heat conduction or current flow.

Dust observations at orbital altitudes surrounding Mars

Date: 2016-01-08
Speaker: Jayesh P. Pabari
Venue: Room #006 (Thaltej campus)

Abstract

Recent developments on Gravitational Collapse Final States

Date: 2016-01-07
Speaker: Prof. Pankaj Joshi
Venue: Room No. 469

Abstract

The final fate of massive collapsing matter clouds and their dynamical evolution has been a fundamental topic in black hole physics and its applications to relativistic astrophysics for the past many years. While the general theory of relativity predicts a necessary occurrence of a space-time singularity in such a scenario, the formation of event and apparent horizons in gravitational collapse is very much a subject of current investigations. In fact, it is the formation and behaviour of the apparent horizon that decides whether the singularity of collapse is enveloped in a black hole or whether it may be visible for far away observers in the space-time. We point out that the apparent horizon and trapped surface formation is determined in terms of the initial data for collapse and the allowed evolutions by the Einstein equations. The black hole and naked singularities in gravitational collapse involve key open issues such as genericity and stability aspects related to these outcomes. We shall discuss some of these issues, including recent implications for astrophysics such as the nature and structure of accretion disks around black holes and singularities and very high energy particle collisions around these objects.

Mid-infrared dust and molecular features in Post-Asymptotic Giant Branch/Proto-Planetary Nebulae

Date: 2016-01-07
Speaker: Mr. V. Venkataraman
Venue: Room # 006 (Thaltej Campus)

Abstract

Stars with low and intermediate mass evolve along the Asymptotic Giant Branch (AGB) after their core hydrogen and helium burning. As the star evolves along the AGB phase it loses mass at an increasing rate until it is totally obscured by its own circumstellar envelope. As the central star evolves to higher temperatures and the circumstellar envelope gets detached from the stellar photosphere and drifts far off, its total spectral energy distribution (SED) becomes 'double-peaked' suggesting the onset of post-AGB (PAGB) or proto-planetary nebulae (PPNe) phase of evolution. The mid-infrared (IR) spectra and modeling of SED on a large sample of PAGB/PPNe objects will be presented in the talk. The mid-IR spectra of these samples showed a variety of features including the stretching and bending vibrations of polycyclic aromatic hydrocarbons (PAHs). The correlation of the derived physical and circumstellar parameters from the SED models with the strength of the observed PAH features will be discussed. The first rare detection of fullerenes in one of the source and its implication on the circumstellar chemistry will be discussed.

Quantum Information Processing: Implementation Schemes and Quantum Memory

Date: 2016-01-01
Speaker: Dr. Sandeep Goyal
Venue: Room No. 469

Abstract

The central aim of the quantum information processing (QIP) is to extend information processing (including computation and communication) in regimes where quantum effects are significant. QIP uses the states of a multilevel quantum system as the basic unit of information. To be useful, a quantum system needs to be both isolated from its environment and easy to control, thus placing a stringent requirement on its physical realization. Photons interact weakly with their environment and are in this respect suitable candidates for QIP. In this talk, I will present photonic implementation schemes for a number of QIP tasks. While some of the QIP tasks such as quantum walks, can be implemented using intense laser pulses (classical light), other protocols such as quantum teleportation, require reliable on demand single photon sources. Quantum memories, i.e., systems capable of storing a single photon, can be used to develop a single-photon source. Hence, constructing efficient and robust quantum memories would pave the way for performing QIP tasks efficiently. Here I will show that quantum memory consists of atomic frequency combs, beside storing a single photon efficiently, can be used for creating genuine multipartite entangled states in macroscopic systems. Finally, I will present an experimentally accessible method to witness this entanglement.

Thermal Inertia Estimation along Traverse of Mars Curiosity Rover inside the Gale Crater

Date: 2016-01-01
Speaker: Subhadyouti Bose
Venue: Room #006 (Thaltej campus)

Abstract

2015

Heating and Dynamics of the Solar Active Regions

Date: 2015-12-31
Speaker: Prof. Durgesh Tripathi
Venue: Room # 006 (Thaltej Campus)

Abstract

Biogeochemical studies of Asia's second largest lagoon during onset of monsoon

Date: 2015-12-29
Speaker: Ms. Rupa Mukherjee
Venue: Ground Floor Lecture Hall

Abstract

The mechanism of nitrogen (N) transport and transformation is very important for freshwater biogeochemistry as the source and sink of dissolved inorganic nitrogen (DIN) can act as an indicator for the autotrophic and heterotrophic nature of the water body. Studies have shown that coastal lagoons are the important source of inorganic carbon to the atmosphere, though its size is small compared to ocean. Chilika lagoon, 64.3 km long and 20.1 km wide, is pear shaped shallow water body(average depth ~ 1.5 m) located on the east coast of India. Chilika is India?s largest lagoon. We measured the natural abundance isotopic composition ( delta-13C and delta-15N) and concentration of particulate organic carbon (POC) and particulate organic nitrogen (PON) covering 16 stations including all sectors of the lake during onset of monsoon (22nd-29th June, 2015). Experiments to measure assimilation rates of inorganic nitrogen were also carried out and lake-wide DIN budget of the lake was estimated. The overall biogeochemistry of the lake will be discussed during the talk.

Detecting Dipolar Dark Matter in Beam Dump Experiments

Date: 2015-12-29
Speaker: Dr. Soumya Rao
Venue: Room No. 469

Abstract

We study interaction of low mass dark matter within beam dump experiments. In particular we study the dipolar dark matter model which assumes that the dark matter couples to Standard Model particles via its electric or magnetic dipole moment. We analyse the constraints on this model in the context of a particular beam dump experiment E613 conducted in the Fermilab. We compare the bounds from other experimental data, such as helioseismological data and direct detection experiments.

Atom induced correlation and anti-correlation features in noisy light fields under electromagnetically induced transparency condition

Date: 2015-12-29
Speaker: Dr. Ashok Kumar
Venue: G F Lecture Hall

Abstract

Understanding the coherent interaction between light and matter is important in many aspects of quantum information sciences. We have embarked on a study of coherent interaction of light fields with cold ensemble of ^{87}Rb atoms under electromagnetically induced transparency condition. We will talk about our results on the noise correlation spectroscopy for two laser fields interacting with cold ^{87}Rb atoms. On keeping one beam at atomic resonance and scanning the detuning of the other around the resonance, a symmetric correlation spectrum with correlation and anti-correlation features at different two-photon detunings is observed. In an another study of noise correlation spectroscopy for a resonant fixed beam, we found that the correlation spectra depend on "which way the detuning of other beam is being scanned". A beautiful Physics dealing with the effect of light induced forces in cold atoms explains our seemingly counter-intuitive results in the correlation spectra.

Physics with ultra high energy neutrinos

Date: 2015-12-28
Speaker: Dr. Sushant Raut
Venue: Room No. 469

Abstract

The IceCube experiment at the South Pole has been constructed to observe ultra high energy neutrinos. These neutrinos, which arrive from extra-galactic sources, have energies in the TeV-PeV range and beyond. A study of these neutrinos complements the neutrino data collected by solar, atmospheric, reactor and accelerator-based neutrino beams. This talk discusses the analysis of IceCube data in the context of CP violation and neutrino decay. For specific source flavour ratios of astrophysical neutrinos, we present our fit to the CP-violating phase. Further, our analysis places constraints on the flavour ratio of astrophysical neutrinos. We also discuss the bounds that can be placed on neutrino decay lifetime.

Indian monsoon intensification and its variabilities on millennial and geological time scales

Date: 2015-12-22
Speaker: Dr. Sajid Ali
Venue: Ground Floor Lecture Hall

Abstract

The Asian Monsoon is a substantial component of the global climate system which affects over 3 billion people living in the area and this is estimated to be over 4 billion by 2050. This large population depends on monsoon rainfall for agriculture, hydroelectric generation and industrial development as well as basic human needs and requires strategies to cope with variations in the timing, intensity and duration of the monsoon. The Asian Monsoon is composed of two sub-systems; the Indian monsoon (also called South Asian monsoon) and the East Asian monsoon. The Indian Monsoon (IM) has displayed a changing relationship with ENSO over recent decades that may be related to global warming and has become less predictable in the last 25 years. Since we have only one century of instrumental data for the IM we must look to paleoclimate proxy records to better understand past IM variability and improve future predictions. New results of mineralogy and radiogenic isotope compositions suggest Indian monsoon well developed around 25 Ma ago and controlled by variable factors at different time scales. The millennial scale variabilities were predominantly controlled by Northern Hemisphere Glaciation (NHG) whereas Himalayan tectonics played vital role in larger scale variabilities. Results from Andaman Sea and Indian Ocean along with Arabian Sea will be considered to discuss Indian monsoon at different time scales.

Optical Tweezers to address some biological problems

Date: 2015-12-21
Speaker: Basudev Roy
Venue: G F Lecture Hall

Abstract

Optical tweezers is a very versatile tool. In this talk, this tool has been used to address a couple of questions in biology. First, we ask how does the kinesin motor 'walk' on a microtubule? In order to answer this question, a birefringent liquid crystal microparticle was attached to the kinesin and the rotation of the particle studied as the kinesin moves on the microtubule. It was observed, quite in contrast to the expected 'asymmetric mechanism', that it actually exhibits the symmetric one while simply turning in one sense during motility. We also show that the kinesin can be twisted by 45 degrees without damage to the molecule and released to observe relaxation. In the second part of the talk, a new technique of determining asymmetry of arbitrary objects trapped in tweezers relying upon the cross correlation of the rotational Brownian motion and translational Brownian motion is demonstrated. This technique is applied to hypotonic RBC's to show the degree of anisotropy.

Energisation of particles from magnetic reconnection

Date: 2015-12-18
Speaker: Rohit Sharma
Venue: USO Seminar Hall

Abstract

The Solar Corona is fascinating. Coronal heating requires either a mechanism to transport heat to the corona or to generate heating in the corona, or both. Currently, the magnetic reconnection process is believed to be the dominant heating mechanism. Here we explore the energy dissipation in magnetic reconnection in small resistivity limits under the magnetohydrodynamics approximation. In addition, we also ask the question - how does the dissipated energy manifest itself ? To study this, we examine the dynamics of test charged particles at the site of magnetic reconnection. We focus on acceleration and formation of particle beams. The talk will summarise initial results from this study.

Topic: Solar observations with MWA

Date: 2015-12-18
Speaker: Divya Oberoi
Venue: USO Seminar Hall

Abstract

Estimation of dust variability and scale height of atmospheric optical depth (AOD) in the Valles Marineris on Mars by Indian Mars Orbiter Mission (MOM) data

Date: 2015-12-18
Speaker: Manoj K. Mishra
Venue: Room #006 (Thaltej campus)

Abstract

A radio relic in CIZA J0649.3+1801 ?

Date: 2015-12-17
Speaker: Ms. Kamlesh Rajpurohit
Venue: Room # 006 (Thaltej Campus)

Abstract

Galaxy clusters form through a sequence of mergers of smaller galaxy clusters and groups. During mergers large scale shocks are driven into the intracluster medium (ICM), these shocks accelerate electrons to relativistic speeds. Together with magnetic fields these electrons emit synchrotron radiation and may form so-called radio relics. In observations radio relics are found to be elongated, peripheral, polarized, Mpc-scale diffuse synchrotron sources. Relics are generally found in merging systems supporting the scenario that they trace shock fronts. There is a evident that they have magnetic fields at the micro-gauss level but difficult to conclude. Their structure and origin is still enigmatic, however polarization plays a key role to distinguish them from other extragalactic objects. A diffuse elongated radio source has been found in a very less-studied galaxy cluster CIZA J0649.3+1801. I will present Westerbork Synthesis Radio Telescope (WSRT) observations of CIZA J0649.3+1801 at 18, 21 and 25 cm. We find that the source has a very steep spectrum (alpha=1.83), for radio relics it is unusual to have such a steep spectrum. On the other hand, the polarization analysis reveals that the source is polarized (8-14%) and has ordered magnetic field with B-vectors perpendicular to the source extension, favouring relic origin. Rotational measure (RM) maps shows strong galactic foreground emission in the direction of CIZA J0649.3+1801. We aim for unveiling the nature of the source by studying its Faraday spectra..

The Phenomenal 2015 Outburst of the Black-Hole X-ray Binary, V404 Cyg

Date: 2015-12-08
Speaker: Dr. Kunal Mooley
Venue: Room # 006 (Thaltej Campus)

Abstract

On 15 June 2015, the Swift Burst Alert Telescope detected an X-ray flare from V404 Cyg. The AMI-LA radio telescope was robotically triggered, revealing a bright and declining radio flare. This was the beginning of an energetic outburst that was to last for several weeks, at the end of which, the entire accretion disk of the X-ray binary would be blown away. An intense panchromatic observing campaign of the outburst was carried out using ground-based and space-based observatories, involving both professional and amateur astronomers worldwide. In this talk, I will present the observational data gathered during V404 Cyg's 2015 outburst, some of the early results from their analyses, and describe the X-ray and radio observations that have helped paint a stunning picture of the accretion and jet processes taking place during the outburst. I will conclude by giving the avenues where ASTROSAT and contemporary radio telescopes will be able to make significant advances in our understanding of X-ray binaries similar to V404 Cyg.

A study of nitrogen dynamics in soils of India

Date: 2015-12-08
Speaker: Ms. Niharika Sharma
Venue: Ground Floor Lecture Hall

Abstract

Study of terrestrial nitrogen cycling is necessary as it plays an important role in growth and development of plants growing in that ecosystem. Rates of various processes within nitrogen cycle like mineralization and nitrification determine the presence or absence of nutrients and hence the growth of plants and microbes in that particular ecosystem. In India, net rates of mineralization and nitrification have been frequently studied but no literature is available for gross rates of these processes in soils of India. Gross rates are important in order to understand actual production and consumption of individual nutrient, establish and redefine land management and fertilizer application practices and thus to achieve sustainable development. This talk will discuss the attempts being made towards measuring these important rates in different ecosystems of India.

IF THERE IS HEAVEN ON EARTH

Date: 2015-12-07
Speaker: Prof. Biswarup Mukhopadhyaya
Venue: Room No. 469

Abstract

-NA-

Towards complexity via the Propargyl Route

Date: 2015-12-04
Speaker: Bhalamurugan Sivaraman
Venue: Room #006 (Thaltej campus)

Abstract

Phenomenology of active galaxies from parsec to megaparsec scale: A multiwavelength view

Date: 2015-12-03
Speaker: Dr. Veeresh Singh
Venue: Room # 006 (Thaltej Campus)

Abstract

Nearly all galaxies host SuperMassive Black Holes (SMBHs) of the order of million to few billion solar mass, in their centres. A galaxy is classified as active galaxy or Active Galactic Nuclei (AGN), when SMBH is in accreting phase, which in fact, depends on the availability of matter in its vicinity. SMBH accretes matter via formation of accretion disk and also ejects a fraction of accreted matter via outflowing bipolar collimated jets. In a subclass of AGN called radio galaxies, jets are powerful enough to plough through interstellar medium and span up to even megaparsec scale entrenching into intergalactic medium. We use multiwavelength observations of AGN to probe inner structures at parsec scales to outer structures up to megaparsec scales. X-ray analysis of AGN emission infers the presence of obscuring torus at parsec scales around AGN and thus validates orientation based unification model. While radio observations help us in probing jet-lobe structures from parsec to megaparsec scales. It is found that radio galaxies exhibit variety of radio morphologies that can be understood by evolutionary scenario in addition to viewing angle effects. Few radio galaxies are found to show two pairs of jet-lobes and thus offer a direct evidence for episodic AGN activity.

Laser absorption based isotope analysers for stable isotopes of oxygen (16O, 17O and 18O) and hydrogen (1H, 2H) in water, and carbon (12C and 13C) in CO2 and CH4.

Date: 2015-11-30
Speaker: Mr. Thomas Gottschalk
Venue: Ground Floor Lecture Hall

Abstract

Cavity Ring Down Spectroscopy (CRDS) based laser isotope analysers for oxygen and carbon isotopes are slowly replacing conventional IRMS, particularly for water, vapor, CO2 and CH4 samples. Achievable precision is reported to be comparable to IRMS or even better. Simultaneous measurement of dD, d18O and d17O in water or vapor and field deployability are features exclusive to this new generation equipment. Technical aspects of this new isotope analytical technique will be discussed in the special semiar.

Generation of Perfect Vortex of variable size and its effect in angular spectrum of the down-converted photons

Date: 2015-11-20
Speaker: Mr. Jabir M V
Venue: G F Lecture Hall

Abstract

Recent development in the field of structured beams have resulted in a special class of optical vortices, known as perfect vortices (PVs), where the radius of the vortex ring is independent of its order. Conventionally, the PVs are generated through the Fourier transformation of Bessel-Gauss (BG) beam. As a result, variation in the size of such vortices requires complicated imaging systems. Howeve, we have devised a simple experimental scheme to generate and vary the size of the PVs using a convex lens and an axicon. In this talk I will discuss on our recent results on generation of variable size perfect vortex beam of different orders and their effect in the angular spectrum of spontaneous parametric down-converted photon.

Developmental status of STEPS payload

Date: 2015-11-20
Speaker: Shiv Kumar Goyal
Venue: Room #006 (Thaltej campus)

Abstract

Noble gases in Apollo 15 Foils, Genesis Targets and Santa Lucia (2008) Chondrite

Date: 2015-11-13
Speaker: Ramakant R. Mahajan
Venue: Room #006 (Thaltej campus)

Abstract

Making Gravity maps with satellite borne Atomic Clocks

Date: 2015-11-10
Speaker: Prof. Subhendra Mohanty
Venue: Room No. 469

Abstract

Gravity maps over a terrain give information of the underground density variations and can be used to map subterranean acquirers, hydrocarbon and mineral deposits. The advances in the accuracy of atomic clocks is now such that General Relativistic corrections to Newtons gravity are measurable and these can be used to make accurate maps of "Geoid Anomalies" or local subterranean density variations. As a byproduct, accurate measurements of atomic frequency shifts in the gravitational field of the Earth can be used to test Einstein's General Relativity. This talk is a theory backup of the GMAP (Gravity Map) proposal which the Theory Division is putting forward for approval in the next plan.

Study of clouds over Ahmedabad using Ceilometer and Satellite

Date: 2015-11-09
Speaker: Rajesh Vaishnav
Venue: Ground Floor Lecture Hall

Abstract

Clouds play a vital role in the Earth's atmosphere, weather forecasting and air transportation safety. To understand the influence of clouds on weather, cloud base height observed during 2014 have been extensively studied using ceilometer over Ahmedabad. Ceilometer is the low power eye safe mini-Lidar specially used for the detection of cloud base height. Preliminary results obtained from the ceilometer measurements and statistical analysis of clouds base height will be presented. A comparative study of clouds using ground based and satellite observations have also been done. Further, efforts have been made to derive boundary layer over Ahmedabad.

Innermost structure of quasars using optical interferometry and reverberation mapping

Date: 2015-11-04
Speaker: Dr. Suvendu Rakshit
Venue: Room # 006 (Thaltej Campus)

Abstract

The broad line region (BLR) of Active Galactic Nuclei (AGNs) contains the high velocity gas clouds transporting material from the dust torus to the accretion disk around the central super massive black hole (SMBH). Unveiling BLR structure is critical to understand the accretion mechanism driving the SMBH evolution and shaping the AGN inflows, outflows and jets. Reverberation Mapping (RM) constrains the BLR geometry, kinematics, mass and equivalent linear size with parameter degeneracies and fudge factors depending from the source geometry. Optical Interferometry (OI) yields independent constrains on BLR structure, mass and equivalent angular size. In this context I will present a 3D geometrical model and kinematical model of BLRs that simultaneous predicts all RM and OI signals, and the result of our first optical interferometric observation of BLR of 3C273. I will also talk about how to use quasars to estimate distances using "quasar parallax".

Global surface ozone observations and analyses-Insights from the WMO Global Atmosphere Watch Programme and the Tropospheric Ozone Assessment Report

Date: 2015-11-02
Speaker: Martin Schultz
Venue: Ground Floor Lecture Hall

Abstract

Ozone is an atmospheric trace gas which is important to mankind in several regards: first, it is a harmful air pollutant affecting health and ecosystems, second, it acts as greenhouse gas and is the second or third most important radiative forcing agent, and, third, in the stratosphere it protects the life on Earth from harmful UV radiation. Due to anthropogenic activities and possibly climate change, the concentrations of ozone in the lower atmosphere have changed considerably from pre-industrial times to present. Nowadays, measured ozone concentrations near the surface are almost twice as large as when ozone was first measured reliably in the 1950s or 1960s. In the troposphere, ozone is formed through chemical reactions of multiple precursors, and because of the large variability of emissions of such precursors, ozone concentrations also vary substantially even on regional scales. The World Meteorological Organisation coordinates the Global Atmosphere Watch Programme to establish reliable, long-term measurements of trace gases and other atmospheric constituents around the globe. Together with data from various regional contributing networks, the surface ozone observations collected in GAW allow for a reasonable assessment of tropospheric ozone changes, although many world regions are still severely under-sampled. In the Tropospheric Ozone Assessment activity, a large group of international researchers attempts to analyze and synthesize all available information on tropospheric ozone and evaluate recent ozone changes. In Julich, these activities are supported through building up the world's largest collection of surface ozone data. These data are stored in a relational database and made available for research use through a comfortable web interface. The presentation will give an introduction to tropospheric ozone, the current measurement network, its global distribution, and the status of the TOAR database.

Degenerate Supersymmetry

Date: 2015-11-02
Speaker: Dr. Ketan Patel
Venue: Room No. 469

Abstract

A degenerate supersymmetric particle spectrum can escape constraints from flavor physics and at the same time evade limits from the direct searches. I will discuss various indirect constraints and phenomenological aspects of such a possibility.

A near range LED Mini Lidar for air and dust monitoring

Date: 2015-10-30
Speaker: Y B Acharya
Venue: Room #006 (Thaltej campus)

Abstract

Fun with Phases

Date: 2015-10-27
Speaker: Dr. Ipsita Mandal
Venue: Room No. 469

Abstract

We discuss some interesting classical and quantum phase transitions. The classical 2d spin 1 Blume-Capel model is a non-integrable model, but it exhibits a tricritical point described by a CFT which can be located only numerically. We show how we can determine this point using the concepts of Entanglement entropy, employing classical Monte Carlo simulations coupled with the knowledge that the critical theory is a minimal model with c=0.7. In the next part, we discuss topological phases. Certain real parameters of a Hamiltonian, when continued to complex values, can give rise to singular points called exceptional points (EP's), where two or more eigenvalues coincide and the complexified Hamiltonian becomes non-diagonalizable. We show that for a topological superconductor with a chiral symmetry, one can find EP's associated with the chiral zero energy Majorana fermions bound to a topological defect/edge. Exploiting the chiral symmetry, we propose a formula for counting the number (n) of such chiral zero modes. We also establish the connection of these solutions to the Majorana fermion wavefunctions in the position space. Finally, we conclude that EP's cannot be associated with the Majorana fermion wavefunctions for systems with no chiral symmetry, though one can use our formula for counting n, using complex k solutions where the determinant of the corresponding BdG Hamiltonian vanishes.

An innovative approach towards operational forecasting of L-band ionospheric scintillations over the Indian longitudes: progress and problems

Date: 2015-10-26
Speaker: Sneha Yadav
Venue: Ground Floor Lecture Hall

Abstract

The equatorial plasma bubbles and the associated L-band scintillations are some of the most important topics in the space weather physics owing to their substantial impact on the satellite based radio communication and navigation applications. In the recent times, a novel method has been developed to forecast the occurrence pattern of the scintillation over the Indian longitudes. In this talk, I would discuss about the series of work that lead to the generation of forecasting model. Some recent results will also be presented on the comparison of the forecast occurrence pattern and the actual occurrence pattern of plasma bubble as observed by Communication/Navigation Outage Forecasting System (C/NOFS) satellite and scintillating irregularities as monitored by GPS satellites. The talk will highlight the significant progress made in the formulation of this forecast model along with the limitations.

Radiation effects on silicon drift detector

Date: 2015-10-23
Speaker: M Shanmugam
Venue: Room #006 (Thaltej campus)

Abstract

Altitudinal Variability of Quiet-time Plasma Drifts in the Equatorial Evening Ionosphere

Date: 2015-10-19
Speaker: Debrup Hui
Venue: Ground Floor Lecture Hall

Abstract

In continuation to our discussions on altitudinal variation of plasma drifts we will explore how the vertical drifts change with altitudes during late afternoon and evening hours when the electrodynamic properties in the ionosphere change rapidly. For the first time using drifts up to 2000 km, we have shown the drifts increase and decrease below and above the F-region peak before becoming height independent. These structures arise to satisfy the curl-free condition of electric fields in low latitudes. The altitudinal gradients of vertical drifts are balanced by a time derivative of the zonal drifts to satisfy the curl-free condition of electric fields. We have shown how these structures evolve with local time around the dusk sector and change with solar flux. During solar minimum, the peak region can go well below 200 km. The present-day electric field models do not incorporate these gradients, particularly in the evening sectors when they change very rapidly. Very often their results do not match with the observations. Including these gradients along with proper magnetic field models will improve the model results and accuracy of our navigation, communication, and positioning systems.

Study of layered deposits in Schiaparelli Basin, Mars

Date: 2015-10-16
Speaker: Samarpita Sarkar
Venue: Room #006 (Thaltej campus)

Abstract

High-power, high-repetition-rate, Yb-fiber laser based femtosecond source at 355 nm

Date: 2015-10-16
Speaker: Mr. Apurv Chaitanya
Venue: G F Lecture Hall

Abstract

High-power, ultrafast ultraviolet (UV) radiation at high repetition rate is of great interest because of its variety of applications in many fields of science and technology. In this talk I will discuss on our recent work on development of such a UV source. Using nonlinear wavelength conversion techniques on an Ultrafast ytterbium fiber based Laser, we have generated ultrafast UV radiation at 355 nm with an output power as high as 1.06 W.

Wigner distributions of quark

Date: 2015-10-15
Speaker: Dr. Sreeraj Nair
Venue: Room No. 469

Abstract

Wigner distribution functions are quasi-probabilistic functions that can provide simultaneous information about the distribution in the momentum and position space. We study the Wigner distribution of quark and gluon in the dressed quark model. We also calculate the kinetic and canonical orbital angular momentum of quark and gluon in this model.

Library's Role in facilitating Research

Date: 2015-10-14
Speaker: Dr. Nishtha Anilkumar
Venue: USO Seminar Hall

Abstract

Isotopic Characterization of Indian Precipitation: Insights about hydro-meteorological Processes

Date: 2015-10-13
Speaker: Mr. Harsh Oza
Venue: Ground Floor Lecture Hall

Abstract

The SW summer monsoon (June-Sept), NE winter monsoon (Oct-Dec), Western Disturbances (Jan-Apr) and local recycling are the four major contributors to precipitation, governing water availability not only in India but also five other countries (Bangladesh, Bhutan, Nepal, Pakistan and Sri Lanka) of the Indian Sub-continent. This region covers only ~3.2% of the global land area but accommodates ~23.2% of the global population. While seasonal pattern of rainfall and underlying processes are broadly understood, the finer details such as eastern limit of the western disturbances, regions prominently affected by local recycling, effect of large wetlands in Northeast India, etc. is still poorly understood. Oxygen and hydrogen isotopes in precipitation can provide some insights on some of these aspects. Under aegis of the IWIN National Programme efforts were made to isotopically characterize the precipitation monitored at more than 40 stations across India for up to four years. Insights about Hydro-meteorological processes obtained from spatio-temporal variation in isotopic composition of precipitation will be discussed in this presentation.

Altitudinal Variability of Quiet-time Plasma Drifts in the Equatorial Ionosphere

Date: 2015-10-12
Speaker: Debrup Hui
Venue: Ground Floor Lecture Hall

Abstract

Ionospheric plasma drift data from Jicamarca radar measurements during day time have been used to study, for the first time, the climatology of altitudinal variations of vertical and zonal plasma drifts in low latitudes during day time. We observed, for the vertical plasma drifts, a small but positive slope in the morning and a negative slope in the afternoon hours. The drifts change mostly linearly from E to F region altitudes except in the morning hours of May-June when the gradient are very small. The zonal drifts show highly nonlinear slopes at the lower altitudes and small negative slopes at the higher altitudes. We also studied the altitudinal profiles of vertical drifts during late afternoon and evening hours, when the electrodynamic properties in ionosphere change rapidly. The drifts increase and decrease below and above F region peak respectively before becoming height independent. These structures arise to satisfy curl free condition of electric fields in low latitudes. Including these gradients along with proper magnetic field models will improve the model results and accuracy of our navigation, communication and positioning systems.

Temporal characteristics of Dunes: Deciphering the wind depositional environment of Mars

Date: 2015-10-09
Speaker: Poornima KV
Venue: Room #006 (Thaltej campus)

Abstract

Study of layered deposits in Schiaparelli Basin, Mars

Date: 2015-10-09
Speaker: Samarpita Sarkar
Venue: Room #006 (Thaltej campus)

Abstract

Study of nonlinear optical properties of nanostructured TiO2 thin films decorated with noble metal nanoparticles

Date: 2015-10-09
Speaker: Dr. Avesh Kumar
Venue: G F Lecture Hall

Abstract

Au-TiO2 nanoparticles are expected to have better nonlinear optical properties for its applications in optical switching, optical limiting and other optical devices. We synthesize Au-TiO2 nanoparticles by sol-gel process and deposit on silicon substrates to form nanocrytalline Au-TiO2 thin films using spin coating method. These thin films are analysed using different characterization techniques such as X-ray diffraction, UV-visible absorption etc. Next, we measure the nonlinear refractive index and nonlinear absorption coefficient of these metal doped TiO2 nanocrystalline films using the z-scan technique. In this talk, I will be explaining the synthesis of these nanocrystalline thin films, its characterization techniques and present the results obtained.

Unravelling Medium Effects in Heavy Ion Collisions with jets

Date: 2015-10-08
Speaker: Dr. Rishi Sharma
Venue: Room No. 469

Abstract

We propose a new observable to analyze events with jets in heavy ion collisions. The observable measures how a thermal medium affects the multiplicity and distribution of energetic particles in a jet. Using few known models for energy loss and jet quenching, we demonstrate its capability to distinguish the physics of these models.

From Fading to Features: Ionosphere over Thumba 1965-67

Date: 2015-10-05
Speaker: Harish Chandra
Venue: Ground Floor Lecture Hall

Abstract

With the establishment of a rocket launching station at Thumba, close to the magnetic equator, an ionospheric station was set up by PRL in 1963. Spaced receiver drift measurements in the E-region were started in November 1963 followed by radio soundings from an automatic ionosonde C-4 from October 1964. Riometers at 21.3 and 16.5 MHz and later on in 1966 radio beacon measurements at 20, 40 MHz using orbiting explorer satellites were the other instruments that operated from Thumba. Multi-technique investigations in the virtually unexplored magnetic equatorial region resulted in several new features of the equatorial ionosphere. Brief summary of some of the results is presented with focus on the use of fading of radio waves as a powerful diagnostic tool.

Intensity correlation and spatial modes of light

Date: 2015-09-29
Speaker: Prof. R.P. Singh
Venue: USO Seminar Hall

Abstract

Intensity correlations, first explored by Hanbury Brown and Twiss in Astronomy, have played an important role in understanding the nature of light. Starting with sizing of stars to understanding the phase transitions and folding of protein molecules, it has found numerous applications in different fields of science. After introducing this versatile technique we will discuss how it can be used to discriminate different spatial modes of light. Some possible applications to solar physics will also be discussed.

Study of ozone and precursor gases at an urban site of Udaipur

Date: 2015-09-29
Speaker: Ravi Yadav
Venue: K. R. Ramanathan Auditorium

Abstract

Udaipur is one of the most important tourist destinations in India. Air quality measurements have been done under the Modeling Atmospheric Pollutants and Networking (MAPAN) program of MoES. At this site, continuous measurements of surface ozone (O3), carbon monoxide (CO) and oxides of nitrogen (NOx) have been done since year 2010. We have investigated the features of diurnal and seasonal variations of trace gases. The relationships between trace gases and role of meteorological parameters have been studied. I will also present my research plan and progress to study some of NMHCs which are important precursors of ozone.

REEs concentrations, Nd & Hf isotopic composition in the Arabian Sea: Water Mass mixing vs. particle ? water interaction.

Date: 2015-09-29
Speaker: Mr. K Damodara Rao
Venue: Ground Floor Lecture Hall

Abstract

Properties of Quark-Gluon-Plasma produced in relativistic heavy ion collisions

Date: 2015-09-24
Speaker: Dr. Vinod Chandra
Venue: Room No. 469

Abstract

There are strong indications that relativistic heavy ion collision experiments at BNL/LHC (CERN) have produced the hottest and the most liquid state of the matter. In fact, the shear viscosity to entropy density ratio for the matter there, turns out be the lowest among all the known fluids. This state of the matter is commonly known as quark-gluon-plasma (QGP). At the theoretical front, its existence can be attributed to the confinement-deconfinement phase transition in Qunatum Chromodynamics (QCD: the underlying theory of the strong interaction). The QGP is expected to exist a few micro-second after the big-bang. Relativistic dissipative hydrodynamical modeling of the space time evolution of the QGP has been highly successful in understanding the physics of the strong interaction. The shear viscosity, bulk viscosity, of the QGP and the equation of state (computed using lattice QCD/improved pQCD) need to be specified at the beginning of the hydrodynamical evolution of the QGP. The prime focus will be on the understanding of shear and bulk viscosities of the QGP from the view point of transport theory. We shall also highlight the impact of these viscosity coefficients on the physics of the strong interaction.

COMESEP: Space Weather Forecasting tool

Date: 2015-09-21
Speaker: Prof. Nandita Srivastava
Venue: USO Seminar Hall

Abstract

Estimation of thermal and non-thermal energies using X-ray measurements during impulsive phase of a failed solar eruption

Date: 2015-09-21
Speaker: Upendra Kumar Kushwaha

Abstract

Statistical properties of Umbral Dots

Date: 2015-09-21
Speaker: Rahul Yadav
Venue: USO Seminar Hall

Abstract

MHD simulations of flux rope formation & loop contraction

Date: 2015-09-21
Speaker: Sanjay Kumar
Venue: USO Seminar Hall

Abstract

Interplay of large and small scales: solar corona

Date: 2015-09-21
Speaker: Dr. R. Bhattacharyya
Venue: USO Seminar Hall

Abstract

Solar physics at USO during its formative years

Date: 2015-09-21
Speaker: Prof. Ashok Ambastha
Venue: USO Seminar Hall

Abstract

Engineering interface to MAST project

Date: 2015-09-21
Speaker: Naresh Jain
Venue: USO Seminar Hall

Abstract

Imaging Spectro-Polarimeter for MAST

Date: 2015-09-21
Speaker: Alok Ranjan Tiwary
Venue: USO Seminar Hall

Abstract

Compensation of MAST alignment errors during operation: Influence matrix of M2-Hexapod

Date: 2015-09-21
Speaker: Dr. A. Raja Bayanna
Venue: USO Seminar Hall

Abstract

Present status of MAST

Date: 2015-09-21
Speaker: Prof. Shibu K. Mathew
Venue: USO Seminar Hall

Abstract

Supercomputing the properties of quark gluon plasma

Date: 2015-09-15
Speaker: Dr. Prasad Hegde
Venue: Room No. 469

Abstract

Lattice QCD is the study of QCD, the theory of the strong force, in its non-perturbative regime through the use of powerful supercomputers. In this talk, I will describe its application to the study of the properties of the quark-gluon plasma, which is a new state of matter created through the collision of heavy nuclei. Here, lattice QCD can not only provide quantitative estimates of the pressure, energy density, etc. but, by varying the quark masses for example, also shed light on the nature and order of the phase transition. Recently, the RHIC experiment at Brookhaven Lab launched its Beam Energy Scan program. The goal of this program is to look for the famous QCD critical point that is conjectured to exist at some moderately large value of the chemical potential. We believe that lattice QCD can make important contributions to this program. I will touch upon some of our recent results in this context and describe what should be possible to do in the near future.

Exploration of Venus: Previous studies and Future Mission Concepts

Date: 2015-09-11
Speaker: Debabrata Banerjee
Venue: Room #006 (Thaltej campus)

Abstract

The Bohr-Einstein Debate in Current Perspective

Date: 2015-09-11
Speaker: Prof. Partha Ghose
Venue: Ground Floor Lecture Hall

Abstract

The interpretation of the quantum state function \psi has been of considerable debate since its inception. The most important issue is whether \psi; is an ontic and complete description of physical reality, or is it an epistemic and incomplete state of knowledge about an underlying reality? The Copenhagen school advocated the former interpretation whereas Einstein favoured the latter interpretation. Recently, N. Harrigan and R. W. Spekkens [Found. Phys. vol. 40, pp. 125-57 (2010)] introduced a mathematical framework which has brought about clarity in discussions on ontic versus epistemic interpretations. Surprisingly, several theorems have since been proven within their framework [e.g. M. F. Pusey, J. Barrett, and T. Rudolph, Nature Phys. vol. 8, pp. 475-78 (2012)] which show that \psi-epistemic models are incompatible with standard quantum mechanics. There is a simple argument using time evolution to show that maximally \psi-epistemic models cease to be so with time. It will be argued that an Einstein type epistemic interpretation is still possible by embedding quantum mechanics in a larger Hilbert space of ontic states so that quantum states are a subset of these states, and hence epistemic in character.

Developing of an optical clock using trapped Ytterbium-ion

Date: 2015-09-10
Speaker: Dr. Subhadeep De
Venue: Room No. 469

Abstract

Increasing accuracies of the atomic clocks have wide range of applications in various fields ranging from sophisticated technologies to precision experiments. Now-a-days the state-of-the-art atomic clocks based on forbidden optical transitions has achieved an accuracy of ~10-18, which means 1 s inaccuracy over the age of the universe. Recently we have started developing an atomic clock that will operate at the |2S1/2; F=0, mF=0> - |2F7/2; F=3, mF=0> octupole transition at wavelength 467 nm of a single trapped and laser cooled ytterbium-ion. We will use an electrodynamic (Paul) trap of the end cap geometry for trapping a single ion and perform precision frequency measurements. We have fabricated a prototype of the trap using the design parameters that we have opted through numerical simulations. We have also estimated systematic uncertainties that are expected from our experiment. As of now, we have designed the ion trap, the ultra-high vacuum chamber and optics associated to the laser cooling. We have already fabricated some sub-components of the experiment such as electromagnetically shielded helical resonator for delivering the radio frequency to the trapping electrodes, atomic oven for producing nearly collimated ytterbium atomic beam and various electronic modules. Current status of the experiment and plans will be discussed.

Radiation reaction and the pitch angle changes in a synchrotron source

Date: 2015-09-10
Speaker: Dr. Ashok K. Singal
Venue: Room # 006 (Thaltej Campus)

Abstract

In synchrotron radiation it is always assumed that the pitch angle of a charge remains constant during the radiation process. Using Larmor's radiation formula, Kardashev (1962) first presented the argument that as the radiation is beamed along the velocity vector of the charge, the momentum loss will also be along that direction and therefore the pitch angle of the charge would remain constant during the radiation process. The accordingly derived formulas are used for calculating energy losses of synchrotron electrons in radio galaxies and are the standard text-book material ever since. However, it turns out that this picture is not consistent with the special relativity and that in the case of synchrotron losses, the pitch angle in general varies. While the velocity component parallel to the magnetic field remains unaffected, the perpendicular component does reduce in magnitude due to radiative losses, implying a change in the pitch angle. This apparent paradox gets resolved and one gets a consistent picture only when effects on the charge motion are calculated from the Lorentz's radiation reaction formula. We derive the exact formula by taking into account the change of the pitch angle due to radiative losses. From this we first time derive the characteristic decay time of synchrotron electrons over which they turn from highly relativistic into mildly relativistic ones.

Discoloration of the Taj Mahal due to Ambient Particulate Deposition

Date: 2015-09-07
Speaker: Dr. J. Jaidevi
Venue: Ground Floor Lecture Hall

Abstract

Aerosols refer to a suspension of solid or liquid particulate matter (size ranging from a couple of nanometers to a few tens of microns) in air. Aerosols perturb Earth's radiative budget directly by interacting with the solar/terrestrial radiation and indirectly by modifying the cloud properties, and thereby impact the climate and hydrological cycle. They also adversely impact human health by affecting the cardio-respiratory and central nervous system of human body via inhalation route. The particulate matter, through deposition or processes like acid rain, affects the monuments, paintings etc. The talk will focus on the regional effects of particulate matter on Taj Mahal. Due to its location in the Indo-Gangetic Plains, the effect of particulate matter on Taj Mahal is visible. Deposition of particulate matter on the white marbles of Taj Mahal is discoloring the white marble into brown color thus affecting its aesthetic view. The size, number and chemistry of the particles deposited onto the marbles were obtained using advanced techniques of microscopy and chemical analysis. The optical properties of these particles were modeled using their physical and chemical properties. The surface reflectance of the particle laden marble was estimated using a radiative transfer model. The daylight illumination, response of eye to color and surface reflectance were used to find the color perceived by the eye. The method adopted was a novel method to find the color of the surface loaded with particles. The method was used to find the contribution of natural dust and anthropogenic aerosol involved in discoloration of Taj Mahal marbles.

Principle of Least Action in General Relativity

Date: 2015-09-03
Speaker: Mr. Sumanta Chakraborty
Venue: Room No. 469

Abstract

Constructing a well-posed variational principle and characterizing the appropriate degrees of freedom that need to be fixed at the boundary are non-trivial issues in general relativity. I will discuss a few toy examples in classical mechanics and field theory before going into general relativity. For spacelike and timelike boundaries I will show that the action principle for general relativity is well posed, only when a suitable counter-term [the Gibbons-Hawking-York (GHY) counter-term] is added to the action principle. Also I will show that the degrees of freedom to be fixed on the boundary are contained in the induced 3-metric. These results, however, do not directly generalize to null boundaries on which the 3-metric becomes degenerate. In this talk I will address the following questions: (i) What is the counter-term that may be added on a null boundary to make the variational principle well-posed? (ii) How do we characterize the degrees of freedom which need to be fixed at the null boundary?

Imaging Spectrometers in Astronomy

Date: 2015-09-03
Speaker: Mr. Vaibhav Dixit,
Venue: Room # 006 (Thaltej Campus)

Abstract

Imaging Spectrometers in particular FOSC (Faint Object Spectrograph and Camera) kind of designs have become very popular within the astronomical community and they have been used on all major telescope facilities across globe. Due to their ability to easily switch between imaging, spectroscopy and polarimetry modes, these instruments have found huge application in various astronomical studies. Design of such instrument poses several technical challenges in their optical and opto-mechanical configurations. An optimum choice of system parameters like Field of View, Resolution and Spectral Range while still meeting the science goal, is very important while conceiving such instrument. In this talk the speaker will present a general description of the FOSC type instrument and will describe the optical and opto-mechanical design considerations.

Spatial variation of amount effect over peninsular India and Sri Lanka: role of seasonality

Date: 2015-09-01
Speaker: Ms. Lekshmy P R
Venue: Ground Floor Lecture Hall

Abstract

The negative relationship between rain amount and its delta-18-O (amount effect) helps to reconstruct past rainfall variability from proxies (e.g., tree-rings and speleothems). Analysis of new (and published) data of the delta-18-O of monsoon rains and vapor at 9 stations shows that in regions of distinct seasonality in precipitation (e.g., peninsular India), the noise in such reconstructions can be minimized by a careful selection of sites. Peninsular India receives rain from both the Indian summer monsoon (ISM) and the north-east monsoon (NEM). Significant amount effect is observed only where the NEM rainfall is larger than or comparable to ISM rainfall. This is due to the higher quantity of NEM rain with more depleted 18-O relative to ISM rain. NEM rain is more depleted in 18-O because of cyclonic activity over Bay of Bengal, and the 18-O depletion of Bay of Bengal surface waters due to post-ISM river runoff.

Ozone in the Martian Atmosphere

Date: 2015-08-31
Speaker: Ashimananda Modak
Venue: Ground Floor Lecture Hall

Abstract

Though ozone is found in trace amount in the Martian atmosphere, it is important for the stability of the Martian atmosphere. Ozone also plays an important role in the neutral chemistry and is an input to ion-neutral models. In this seminar I will discuss about observations made by SPICAM (SPectral Investigation of the Characteristics of Atmosphere of Mars) on board Mars Express(MEX) and retrieval of ozone and I will show some interesting features of ozone in Martian Atmosphere.

Spectroscopy of aromatic synthesiser: propargyl compounds

Date: 2015-08-28
Speaker: Ms. Taranpreet Kaur
Venue: Ground Floor Lecture Hall

Abstract

Polycyclic Aromatic Hydrocarbons (PAH), are known to be the carrier of several infrared features in the Interstellar Medium (ISM). However, the synthesis of smaller and large PAH molecules were to-date not well understood at astrochemical conditions. However, benzene synthesis from propargyl alcohol in fact had opened the possibility of an entirely new reaction network, the ?propargyl channel to PAH?, on the icy mantles of cold dust grains. From the complex chemical network that prevails in the ISM we could expect a variety of propargyl containing molecules that are present and awaiting discovery. Therefore, it is imperative to understand the physico-chemical properties of propargyl compounds at astrochemical conditions. Here, I will be presenting the first results of propargyl containing compounds such as propargyl ether and propargyl alcohol.

Validation of delta-18-O as a proxy for past monsoon rain by multi-GCM simulations

Date: 2015-08-27
Speaker: Mr. Midhun M.
Venue: Ground Floor Lecture Hall

Abstract

Stable oxygen isotope ratios (delta-18-O) of tree cellulose and speleothem carbonate are useful proxies for past monsoon rain in many tropical regions, as a decrease in rain delta-18-O is observed with increase in rainfall on a monthly time scale. This amount effect varies spatially; therefore a local calibration, with actual measurements of rain amount and its delta-18-Ois required. Such observations, however, are quite limited in space and time. To circumvent this difficulty, many isotope enabled general circulation models (GCMs) are used to aid the interpretation of 18-O proxies; nevertheless, all such simulations taken together are yet to be evaluated against observations over the Indian summer monsoon (ISM) region. Here we examine ten such GCM simulations archived by the stable water isotope intercomparison Group, phase 2. The spatial patterns of simulated ISM rainfall and its delta-18-O are in good agreement with the limited observations available. Simulations nudged with observed wind fields show better skill in reproducing the observed spatio-temporal pattern of rainfall and its delta-18-O. A large discrepancy is observed in the magnitude of the simulated amount effect over the Indian subcontinent between the models and observation, probably because models simulate the spatial distribution of monsoon precipitation differently. Nudged simulations show that interannual variability of rainfall delta-18-O at proxy sites are controlled by either regional (rather than local) rainfall or upstream rain out. Interannual variability of rainfall delta-18-O over the East Asian region is well correlated with ENSO, while it is only weakly correlated over the Indian sub-continent.

Milne-Eddington inversion code forFe-I 6173.33 nm spectral line

Date: 2015-08-24
Speaker: Rahul Yadav
Venue: USO Seminar Hall

Abstract

Inversion techniques are the most powerful and sophisticated tool to infer the magnetic and thermodynamical properties of the solar atmosphere from the interpretation of Stokes profiles. The basic idea of any inversion code is to iteratively fit the observed Stokes profiles with the synthetic profiles. The synthetic profiles are generated by solving the polarised radiative transfer equation (RTE) which assumes a model atmosphere. After optimizing the merit function, the best fit model atmosphere is inferred as the model of the atmosphere. We are developing an inversion code of the radiative transfer equation in Milne-Eddington (ME) approximations. Under ME assumptions the properties of the solar atmosphere are constant with height, except the source function which depends linearly on optical depth. A standard Levenberg-Marquardt least-square minimization method is used to optimize the merit function. The new ME-code, written in IDL, can be used for any photospheric spectral line. To facilitate the comparison, we selected MERLIN inversion code which is a standard inversion code used to invert the spectro-polarimetric data from Hinode. The inversion strategy of the new ME-code, comparison between new ME-code and MERLIN will be discussed in this talk.

Some Highlights: MetSoc2015

Date: 2015-08-21
Speaker: S.V.S. Murty
Venue: Room #006 (Thaltej campus)

Abstract

Spatial distribution of neutral hydrogen in the Milky-way

Date: 2015-08-21
Speaker: Prof. Avinash Deshpande,
Venue: Room # 006 (Thaltej Campus)

Abstract

The atomic hydrogen in our Galaxy has structure on a range of spatial scales. The talk will briefly describe the various probes to study the HI distribution on small and large scales, as well as discuss some of the puzzles these studies created, and their possible resolution.

Vector vortex beam: Generation and Non-coaxial superposition

Date: 2015-08-21
Speaker: Mr. Aadhi A
Venue: Ground Floor Lecture Hall

Abstract

Vector beams are the solutions of vector wave equation and having spatially varying polarization throughout the cross section. These are doughnut shaped beams like scalar vortex beams and ring shaped beams, with phase and polarization being undefined at their center. Such vector vortex beams are classified into four types depending upon the spatial variation in their polarization vector. Recent investigation identifies that vector beams are classically entangled in polarization and orbital angular momentum (OAM) and it can violate Bell?s like inequality. Moreover, demonstration shows that classical entanglement can also be used for teleportation protocols. The generation of all these four types of vector beams using modified polarization Sagnac-interferometer with a vortex lens will be discussed along with the non-coaxial superposition of two vector vortex beams.

Confinement Transition in QCD: Phenomenology and Early Universe Impilcations

Date: 2015-08-20
Speaker: Dr. Abhishek Atreya
Venue: Room No. 469

Abstract

Quantum Chromodynamics (QCD) is the theory of strong interactions, responsible for the binding of nucleus and nucleons as well. One of the peculiar property of QCD is the confinement of `color' charge. The finite temperature formulation of theory predicts a transition from a confined phase to a deconfined phase (Quark Gluon Plasma) at extreme temperature and baryon chemical potential. The phase structure of QCD is very rich owing to its non-abelian nature. Roughly half of the talk would be devoted to provide a brief introduction to the phase structure of QCD, and the onging experimental endeavour to probe it, in a language (hopefully) accessible to non specialists. The later half will be based on the study of QCD Z(3) domains which arise naturally while discussing the confinement-deconfinement phase transition using a Landau-Ginzburg kind of effective potential. We will explore the possibility of spontaneous CP violation in the scattering of quarks and anti-quarks from QCD Z(3) domain walls. This finds interesting implications in Cosmology and also in Heavy Ion Collisions. In context of early universe, we study the effect of this spontaneous CP violation on the baryon transport across the collapsing large Z(3) domain walls (which can arise in the context of certain low energy scale inflationary models). If time permits, then we'll also discuss the quark scattering from Z(3) walls by including the effects of dynamical quarks. This leads to interesting changes in the quark scattering from the Z(3) interfaces.

Observational Studies of Hydrogen Deficient Stars for Investigating their Evolutionary Connections

Date: 2015-08-20
Speaker: Dr. Hema B. P.,
Venue: Room # 006 (Thaltej Campus)

Abstract

R Coronae Borealis (RCB) stars and the hydrogenÂdeficient (H-deficient) carbon stars are the H-deficient and carbon rich F- and G-type supergiants. There are only handful of these stars known in the Galaxy. The origins and evolution of these stars are not yet clear. For my thesis, the origins and evolution of these stars were investigated, 1. By deriving the Galactic RCB/HdC stars' CÂabundances and the 12C/13C ratios, from C2 Swan bands using their highÂresolution spectra, which are potential clues to their origin, and 2. By conducting a lowÂresolution spectroscopic survey for identifying the HÂdeficient stars in the red giant sample of the Galactic globular cluster Omega Centauri, to pinÂpoint their position on the HRÂdiagram. In my talk I will be presenting the observations, methodology, analyses and results of our above mentioned studies.

REE and Mo isotopic study of Permo-Triassic sediments from Spiti Himalaya

Date: 2015-08-14
Speaker: Vinai Rai
Venue: Room #006 (Thaltej campus)

Abstract

Dry ice in the interstellar medium

Date: 2015-08-14
Speaker: Dr. Bhalamurugan Sivaraman
Venue: Ground Floor Lecture Hall

Abstract

Carbon dioxide being one of the most abundant molecules in the InterStellar Medium (ISM) had got the attention of spectroscopist to understand the morphology as it condenses to form ices in the ISM. Laboratory experiments simulating ISM dry ice were performed intensively since the 1980's in all aspects from morphology, reactivity and desorption, where almost all of these studies depended on the infrared (IR) spectroscopy, which eventually had lead to the finding of dry ice in various sources studied by the Spitzer space telescope. However, still there are fresh debates on the morphology of dry ice as it condenses from the gas phase. In this talk, I will review the morphology of dry ice probed using IR spectroscopy and then discuss how our fresh results at VUV wavelengths help understand it better.

An investigation on a long duration prompt penetration event:Insights

Date: 2015-08-10
Speaker: Diptiranjan Rout
Venue: Ground Floor Lecture Hall

Abstract

It is well known that during geomagnetically disturbed conditions the electric field over the dip equator is affected by prompt penetration electric field on many occasions. Theoretically, the effects of prompt penetration are expected to last ~30 minutes as shielding is established at the inner edge of the ring current region. However, observations reveal that the prompt penetration events can continue for hours together. Recently, based on a case study, it is shown that three different types of prompt electric field disturbances, occurring in succession over a period of 6 hours, have affected the equatorial ionosphere-thermosphere system (ITS) on a single night. This investigation shows that the processes constituting long duration prompt penetration events must be understood critically. In the present talk, these results will be discussed.

Origin of Layered Ejecta Craters in Arabia Terra Region of Mars

Date: 2015-08-07
Speaker: S. Vijayan
Venue: Room #114 (Thaltej campus)

Abstract

Catalytic Electron ? A Fundamental Mechanism and its Experimental Verification

Date: 2015-08-07
Speaker: Dr. Daly Davis
Venue: Ground Floor Lecture Hall

Abstract

Low energy free-electrons can be used as a tool to initiate control and manipulate chemical reactions and nanoscale molecular synthesis. The overall sequence that leads to the final products involves resonance capture of low-energy free-electron by a reactant molecule and subsequent formation of an intermediate electron-molecule compound state. Our theoretical studies have made a remarkable proposition that the low-energy free-electron can also act as a catalyst in a chemical reaction. Catalytic activity of the electron is bound to the metastability of the electron-molecule compound state. Followed by this theoretical proposition of catalytic electron, many of the reaction mechanisms including the enzymatic repair of thymine dimer, a photo-damaged molecule, and various reaction steps in electrochemical processes have been attributed to the catalytic activity of the electron. We have also experimentally verified that electron is a catalyst by observing the production of CO2 in a resonant, free-electron capture by formic acid. Our low-energy free electron impact experiment sophisticated with in-situ molecular probing using Fourier transform infra-red (FTIR) spectroscopy shows that the resonant formation of CO2 at 6 eV and 11 eV of incident electron is indeed catalysed by the free-electron. This talk covers the details of theoretical discovery of catalytic electron and its experimental verification using electron impact studies in condensed phase.

Introduction to polarimetry

Date: 2015-08-06
Speaker: Alok Ranjan Tiwary
Venue: USO Seminar Hall

Abstract

Introduction of TD-GC-FID system and analysis of VOCs: Preliminary Results

Date: 2015-08-03
Speaker: Devendra Pal
Venue: Ground Floor Lecture Hall

Abstract

Gas chromatography (GC) is a versatile and powerful technique which has many applications. In PRL, the GC system coupled with a thermal desorption (TD) and a flame ionization detector (TD-GC-FID) has been used for the analysis of several volatile organic compounds (VOC) in air. Recently, instead of liquid nitrogen, the TD system has been widely used for the pre-concentration of gaseous samples containing low concentrations of analytes. I will present operational details of different components of TD-GC-FID system. Ambient concentrations of benzene and toluene were measured at 12 different road junctions of Ahmedabad city during the months of March and April, 2015. Briefly, I will present the site-to-site and day-to-day variation in the mass concentrations of aromatic VOCs (benzene and toluene).

Physical environment of massive star-forming region W42: a multi-scale and multi-wavelength approach

Date: 2015-07-31
Speaker: Dr. Lokesh Kumar Dewangan,
Venue: Room # 469 (Theory Seminar Hall, PRL Main Campus)

Abstract

In massive star formation research, it is extremely difficult to identify a promising sample of the precursors/early critical phases of O type massive stars. In the literature, there are only a handful of massive young stellar objects (MYSOs) known to be associated with highly collimated jets and/or Herbig-Haro (HH) objects. I will present results of an analysis of massive star-forming region W42 using a multi-scale and multi-wavelength approach. These results throw light on the physical environment of W42 on smaller (about 5000 AU) and larger (about 10 pc) scales, helping to understand the formation and interaction of massive stars with their surrounding environment. A bipolar appearance of W42 complex (on scales of about 10 pc) is evident due to the ionizing feedback from the O5-O6 type star in a medium that is highly inhomogeneous. The VLT/NACO adaptive-optics K and Lp images resolved this ionizing source into multiple point-like sources below ~5000 AU scale. In this complex, we have discovered a parsec scale H2 outflow that is driven by an infrared counterpart of the 6.7-GHz methanol maser emission (i.e. W42-MME; stellar mass 19 solar mass and extinction 48 mag). Furthermore, we have investigated a collimated jet-like feature (in the inner 4500 AU) in W42-MME using the VLT NIR adaptive-optics images. The jet is located inside an envelope/cavity (extent ~10,640 AU) that is tapered at both ends and is oriented along the north-south direction. Such observed morphology of the outflow cavity around the massive star is scarcely known and is very crucial for understanding the jet-outflow formation process in massive star formation.

Sulphur in our Solar System and beyond

Date: 2015-07-31
Speaker: Ms Pavithraa
Venue: K R Ramanathan Auditorium

Abstract

Sulphur bearing molecules play their part in the complex chemical network that prevails in the icy bodies of the Solar System and on the cold dust grains of the interstellar medium. With the recent discovery of ethanethiol in the interstellar medium and repeated discovery of carbon disulphide in comets it is imperative to understand these molecules at low temperatures in order to reveal the role played in chemical reactions. In this talk, I will be presenting the first results on sulphur bearing molecules, such as ethanethiol and ammonium dithiocarbamate, in low temperature molecular ices obtained from the new 10 K experimental facility.

Search for gravitational waves from binary blackholes using multi-detector geometrical coincidence

Date: 2015-07-30
Speaker: Dr. Gurudatt Gaur
Venue: Room No. 469

Abstract

Coalescing compact binary consisting of neutron star and/or black hole are the most promising sources of gravitational waves, to be detected by ground-based interferometric detectors like, LIGO, Virgo, GEO, TAMA etc. Data Analysis for the detection of gravitational waves from these sources comprises of a sequence of jobs such as place a template bank, filter the data, do coincidence, etc. We develop a method to determine coincidence among the triggers from various detectors using a metric caculated in the space of IMRPhenomB waveform family. In this talk, I shall discuss the advantages of using this metric in the search of gravitational waves from binary black hole systems in LIGO data.

Results on Night time Equatorial E-region Currents

Date: 2015-07-27
Speaker: Kuldeep Pandey
Venue: K. R. Ramanathan Auditorium

Abstract

Day time large variations in horizontal component of magnetic field recorded on ground based magnetometer are well known and are attributed to strong current flow over equatorial E-region. However, during night time, it is believed that ionospheric conductivity is not large enough to support substantial current. As a consequence, ground magnetic variations during nighttime are considered to be mainly due to magnetospheric currents. There have been very few attempts to either measure or estimate the nighttime ionospheric current. This problem becomes even more severe during disturbed space weather conditions when an accurate estimation of the nighttime base value is difficult. Therefore, it is important to estimate the night time equatorial E-region current strength and its variability. In the present talk, the progress made in this regard will be presented.

Non-separable states of light: Bell violation and Scattering

Date: 2015-07-24
Speaker: Mr. Chitrabhanu
Venue: Ground Floor Lecture Hall

Abstract

We generate classical Bell like states of polarization and orbital angular momentum (OAM) using a laser beam. These are equivalent to the hybrid entangled systems in which two degrees of freedom of a single particle are entangled. We consider a cyclic evolution of the polarization state which introduces a relative phase to the generated Bell state. We observe that the violation of Bellâ??s inequality depends on the relative phase and the choice of our measurement basis. We also show that the non-separability remains preserved under scattering through a random medium like rotating ground glass. We verify this by measuring the degree of polarization and observing the intensity distribution of the beam when projected to different polarization states, before as well as after the scattering.

Electromagnetic instability induced by Neutrino interaction

Date: 2015-07-24
Speaker: Mr. Manu George
Venue: Room No. 469

Abstract

Interaction of lepton with neutrino can modify the lepton wave function. As a result, the presence of neutrino can indirectly modify the photon polarization tensor. It was observed in field theoretical calculations that, left-right asymmetry in neutrino density can contribute to an anti-symmetric term in the photon polarization tensor. In this talk I shall try to construct kinetic theory from non-relativistic Hamiltonian for a spin half system in the presence of neutrino background. I shall also calculate the current and polarization tensor using this kinetic theory.

MHD relaxation in astrophysical plasmas

Date: 2015-07-23
Speaker: Sanjay Kumar
Venue: USO Seminar Hall

Abstract

Instabilities in chiral hydrodynamics

Date: 2015-07-23
Speaker: Mr. Manu George
Venue: Room No. 469

Abstract

Parity violating effects arises from quantum anomalies, play an important role in wide range of areas in physics, from quantum Hall system to cosmology. Chiral magnetic effect(CME) is one of such phenomena arises in the presence of a magnetic field, due to the asymmetry between left-handed and right-handed particle, parameterized by chiral chemical potential μ_5 ≡μ_R − μ_L. The production of huge magnetic field(~10^18 G)in the off central heavy-ion collisions set up an experimental platform for the observation of CME. Recently kinetic theory and hydrodynamics are appropriately modified to describe these quantum anomalies and CME. In this talk I shall briefly discuss about the chiral kinetic theory and linear analysis of chiral hydrodynamics.

Improving hadron resonance gas model

Date: 2015-07-23
Speaker: Mr. Guruprasad Prakash Kadam
Venue: Room No. 469

Abstract

Albeit the canonical non interacting hadron resonance gas (HRG) model is successful in describing (the thermodynamics of) hadronic phase of quantum chromodynamics, it ignores two important features of hadronic matter; that there exist short range repulsive interaction between hadrons and hadron masses are depends on temperature (and baryon density) which is rather upshot of the chiral symmetry. In this seminar I will discuss our current endeavour to improve the canonical non-interacting HRG model with an equation of state accounting for the repulsive interaction between hadrons as well as temperature (and density) dependent hadron masses.

Primordial magnetic field and kinetic theory with Berry curvature

Date: 2015-07-22
Speaker: Mr. Arun Kumar Pandey
Venue: Room No. 469

Abstract

Magnetic fields have been observed not only on small scale but also on large scale of the universe. Depending on the length scale, strength of the magnetic field varies. They play an important role in the formation of astronomical environments like plasma and currents. However it is still not clear from where and how they came into existence. It is usually assumed that the observed magnetic fields were amplified by dynamo mechanism from preexisting seed magnetic fields coherent over scales of the order of 100 Mpc at the time of structure formation. But recent observation suggests that, these seed fields may have generated very early in the universe. In this talk, I shall discuss about generation of Primordial magnetic field using chiral kinetic theory at temperature T> 80TeV.

Excitation spectrum and dispersion relation of binary condensates in quasi-2D optical lattices

Date: 2015-07-22
Speaker: Mr. Kuldeep Suthar
Venue: Room No. 469

Abstract

In this talk, we explore the collective excitations of two-species Bose-Einstein condensates (TBECs) loaded into two-dimensional optical lattices. We develop the Hartree-Fock-Bogoliubov theory with the Popov approximation using the coupled discrete nonlinear Schrodinger equations to analyze the quasiparticle mode evolution of TBEC. We observe the transition from miscible to the immiscible (phase-separated) ground state density profile upon varying the intraspecies (interspecies) interaction for 87Rb-85Rb (133Cs-87Rb) TBEC. At phase separation, the degenerate slosh mode goes soft and gets transformed into an interface mode. This mode regains energy upon further change in the interaction strength. We shall also discuss the character of the excitations using dispersion relation of TBEC in harmonically trapped optical lattices.

Late Quaternary sedimentation in the western India: A geochemical provenance study

Date: 2015-07-22
Speaker: Mr. Anirban Chatterjee
Venue: Nanosims Meeting Hall

Abstract

The western part of Indian sub-continent is home to a unique repository for Quaternary sedimentary deposits, representing different climatic and geomorphic regimes. One of the important steps to understand the landform evolutionary processes is to decipher the source and transport pathways of the sediments deposited in these basins. Rare Earth Element (REE) geochemistry and Sr-Nd isotopic signatures are important tools to decipher sediment provenance. In this talk I would present results of our study carried out in this regard, from Luni river basin, Thar Desert and Ghaggar River.

Imaging polarimeter for Multi Application Solar Telescope

Date: 2015-07-21
Speaker: Alok Ranjan Tiwary
Venue: USO Seminar Hall

Abstract

The Multi‐application Solar Telescope (MAST) is a 50 cm off‐axis Gregorian telescope installed at the lake site of Udaipur Solar Observatory. One of the scientific objectives of MAST is to study the evolution of vector magnetic field on the solar atmosphere and its connection to various solar activities. In order to measure the vector magnetic field in the solar atmosphere, we have developed a Polarimeter for the MAST, which will be used for precise measurements of the Stokes vector at two different wavelengths i.e. at 617.3 nm and 854.2 nm, corresponding to photospheric and chromospheric heights, respectively. The Polarimeter will modulate the polarization signal using two liquid crystal variable retarders (LCVR) along with a linear polarizer (one set each for the above wavelengths).

"LED Mini-Lidar for Air and Dust Monitoring"

Date: 2015-07-20
Speaker: Y. B. Acharya
Venue: Ground Floor Lecture Hall

Abstract

LED mini-lidar is a new concept optical sensor. This employs LED as the detection light source. Due to the wealth wavelength of LED, LED lidar achieves aerosol detection at a specific wavelength, and it makes the detection of aerosol particle size distribution easier. However it cannot replace traditional lidar which uses laser as a light source. We will compare both lidar systems and also discuss its suitability for some applications.

Black Holes in Our Universe

Date: 2015-07-20
Speaker: Dr. Prateek Sharma
Venue: Room No. 469

Abstract

Once a figment of theorists' imagination, Black Holes (BHs) are now astronomically well-established entities. Astrophysical BHs occur in two varieties: supermassive BHs (10^6-10^9 solar mass) at the centers of galaxies and stellar-mass BHs (~10 solar mass) in form of X-ray binaries. I will present astrophysical evidence for BHs, and present theoretical models to understand accretion of matter on to BHs in different conditions. BHs, owing to their strong gravity, are powerful engines which strongly influence their surroundings through mechanical energy (in form of jets) and intense radiation. I will also discuss the central role of supermassive BHs in controlling galaxy formation.

Moderate Glaciation on Mars

Date: 2015-07-17
Speaker: Rishitosh K. Sinha
Venue: Room #114 (Thaltej campus)

Abstract

Quantum information, quantum correlations and many-body systems

Date: 2015-07-17
Speaker: Dr Debraj Rakshit
Venue: Ground Floor Lecture Hall

Abstract

Quantum entanglement is the genuine quantum property of a composite system that forbids individual parties to be attributed with distinct quantum states even if they are far apart from each other. Entanglement has been identified to be an important resource for performing quantum tasks, such as quantum communication and quantum computation. Generation of entanglement in composite systems requires interaction between its subsystems, and hence strongly interacting systems, e.g., quantum spin chains, form physical resources of entanglement. A quantum information perspective on many-body systems generates new ideas and leads to development of novel methods for solving many-body systems. Several concepts developed in quantum information science turn out to be useful tools for detecting co-operative phenomena, like quantum phase transitions. In this talk, I will briefly introduce few key concepts that steer cross-fertilization between these two traditional disciplines of research, and present some of our recent works in this direction. Specifically, I will talk about characterization of quantum correlations in quantum spin systems with defects, and dynamical evolution of entanglement followed by a sudden quench.

Asymmetries in the angular distribution of rare decay Lambda_b --> \Lambda (--> N \pi) l+ l-

Date: 2015-07-16
Speaker: Mr. Girish Kumar
Venue: Room No. 469

Abstract

The semi-leptonic decay Lambda_b --> \Lambda (--> N \pi) l+ l- is mediated by electro-weak loop diagrams in Standard model (SM) and can receive large enhancements from new physics (NP). It gives access to a variety of angular observables and hence offers a rich phenomenology. From the theoretical point of view, exclusive modes suffer from large hadronic uncertainties due to the form factors. One has to find strategies to reduce this form factor dependence by considering certain ratios. In this talk, we start by discussing the angular distribution of the final sate of this decay mode. We discuss angular asymmetries which can be extracted to completely determine this distribution. We then discuss the- important angular observables and appropriate ratios of these angular asymmetries which can be used to test SM.

The multi-disciplinary ground-work for the COSAC GC-MS onboard ESA?s Rosetta mission

Date: 2015-07-16
Speaker: Dr Chaitanya Giri
Venue: G.F. Lecture Hall

Abstract

This seminar will highlight the multi-disciplinary groundwork for the pioneering in situ organic compositional analyses of nuclei surface of comet 67P/Churyumov-Gerasimenko performed by the Cometary Sampling and Composition Experiment (COSAC) in November 2014. COSAC is a Gas Chromatograph-Mass Spectrometer on board the Philae Lander probe of European Space Agency?s Rosetta mission to comet 67P/Churyumov-Gerasimenko.The talk introduces three holistic yet myriad experimental and analytical campaigns, 1) carried out at a synchrotron radiation facility (DESIRS Beamline ? Synchrotron SOLEIL),2) with the COSAC flight spare model (located at the Max Planck Institute for Solar System Research), 3) with the tentative comet surface analogue material ?tholin?(synthesized at NASA Ames Research Center), all directing to the objectives of COSAC subsequent to its landing on 67P.

Variability study of Blazars: A case study of S5 0716+714

Date: 2015-07-16
Speaker: Ms. Navpreet Kaur
Venue: Room # 113 (Thaltej Campus)

Abstract

One of the most spectacular, powerful and mysterious sources in Universe are Active Galactic Nuclei (AGN). Most of them are hosted by elliptical galaxies at high redshifts and contain supermassive black hole (SMBH) at their center. Depending upon their orientation with respect to observer, AGNs have been classified into various sub-classes, out of which, one sub-class is Blazar. Blazars have been known to have their relativistic jets pointed almost towards the line of sight and dominates their emission. Since jets are supposed to be launched from the close vicinity of black hole, blazar study provides an insight to probe deep into the central engine. These sources show emission at all wavelengths (radio - optical - NIR - X-rays up to gamma rays) which is variable at various time-scales ranging from years to few tens of minutes. They also show variability in both, total flux and polarization. Blazar S5 0716+714 is one of our favorite sources, which shows short-term and long-term variability and has been monitored by our group for more than 10 years in optical. Observations have been carried out by PRL's MIRO (Mount Abu InfraRed Observatory) facility at Gurushikhar, Mount Abu. We use two moderate sized telescopes; 1.2 m (f/13) Cassegrain type telescope and 50 cm (f/6.8) CDK20 system with Liquid nitrogen cooled optical CCD camera and EMCCD. We found the source showing unprecedented brightness in late January, 2015. Few results showing intra-night and inter-night variability during last two years for this source will be discussed in the talk.

Speleothem based reconstructed monsoon during Early-Holocene and Late-Pleistocene

Date: 2015-07-14
Speaker: Ms. Shraddha Band
Venue: Nanosims Meeting Hall

Abstract

Speleothems which are cave carbonate deposits occurring in limestone areas can be used to reconstruct past climatic variations, often providing a high-resolution continuous record covering a long-period of time. As ratio of stable isotopes of oxygen in rainfall is amount dependent in tropical sites, for speleothems it is a robust proxy of past monsoon variations. With this motive, stalagmites from two caves having different geographical locations were studied. A stalagmite from Dandak cave that grew between 10 to 9 kyr shows persistent intensification of monsoon since the early part of Holocene, in addition to switching over to a few drought like events for short intervals of time. Another stalagmite from Belum cave covering a time span of 100 kyr (between 190 to 80 kyr) has rather interesting depositional history in accordance with the Marine Isotope Stages-6 to 4. Results from these two caves will be discussed in the seminar.

Characteristics of the sudden stratospheric warming and intra-seasonal oscillations at low latitude stations

Date: 2015-07-13
Speaker: Amitava Guharay
Venue: Ground Floor Lecture Hall

Abstract

The sudden stratospheric warming, a large scale atmospheric disturbance originating at polar stratosphere, significantly affects low latitude atmospheres through latitudinal coupling. Planetary scale waves are surmised to be responsible for driving such large scale disturbances and associated dynamical modifications of the global atmospheric processes. The present study illustrates the features of the strongest major sudden stratospheric warming in the southern hemisphere low latitude station. Intra-seasonal oscillations (ISO) are a class of large scale oscillations of period ~ 20-100 days dominant mostly at equatorial region which control the propagating atmospheric waves of various scales by altering the mean background conditions. Convectively generated waves are responsible for carrying the intra-seasonal features from the lower to the middle atmosphere. Recent results on the behavior as well as comparative features of the ISO from two southern hemispheric low latitude stations will be discussed in the presentation.

Magnetic fields in triggered and spontaneous star forming regions

Date: 2015-07-13
Speaker: Dr. Archana Soam
Venue: Room # 113 (Thaltej Campus)

Abstract

The study of magnetic fields in molecular clouds formed in various environments have enormous potential towards understanding the underlying physics behind the role played by the magnetic fields in the formation of molecular clouds and the subsequent star formation. The closer and isolated molecular clouds provide the fascinating laboratories where the importance of magnetic fields can be explored towards ongoing activities like evolution of the cloud and star formation. My main focus is to explore the magnetic fields morphologies and strength in various environments of molecular clouds to understand the open issue of importance of magnetic fields in interstellar medium. The regions where I have mapped the magnetic fields are broadly classified into the categories viz. triggered star forming and spontaneous star forming sites. In triggered star forming regions, I have chosen the multiple bright-rimmed clouds (BRCs) and cometary globules (CGs) associated to some HII regions surrounded by a high mass star in the center. In a magnetic field dominated scenario for isolated and spontaneous low-mass star formation, the cores are envisaged to gradually condense out of a magnetically subcritical background cloud, through ambipolar diffusion. To understand the evolution of magnetic fields in the cores of different ages (ages determined based onto their chemical evolution), I have studied the magnetic fields in a number of starless/prestellar cores. Magnetic fields morphologies in some of the cores harboring very low luminosity objects (VeLLOs) have also been made. The magnetic field maps are made with the help of optical, NIR and submm polarimetric techniques using observing facilities available in India and abroad.

Surface Energy Budget and Thermal Inertia Estimation using Curiosity Rover REMS Data: Preliminary Results

Date: 2015-07-10
Speaker: Subhadyouti Bose
Venue: Room #114 (Thaltej campus)

Abstract

Interstellar PAHs: IR spectroscopy

Date: 2015-07-10
Speaker: Dr Amit Pathak
Venue: G.F. Lecture Hall

Abstract

The detection of emission bands at 3.3, 6.2, 7.7, 8.6, 11.2, and 12.7 um towards many astronomical objects in the interstellar medium (ISM) has opened up new prospects in observational, laboratory and theoretical molecular astrophysics.These features have been proposed to be emitted by transiently heated large (50 to 100 C-atom) Polycyclic Aromatic Hydrocarbon (PAH) molecules, although no individual PAH has been identified in the ISM yet. In this talk I will be discussing the emission mechanism and the spectroscopy involved. I will also be discussing the mid-IR spectra of interstellar PAHs and its variation based on theoretical spectroscopic studies. The talk will try to cover substituted PAHs as carriers of some of the observed bands.

Dynamics of a Travelling Front

Date: 2015-07-09
Speaker: Prof. Debashis Ghoshal
Venue: Room No. 469

Abstract

Systems with an unstable (metastable) phase and a stable one are often separated by a sharp `wall'. As the size of the region of stability grows, this wall moves as a `travelling front', which may have characteristic universal properties in certain cases. In this talk we will briefly discuss the early history of the travelling front, and then describe a non-local variant that we encountered and studied.

Understanding the properties of Be/X-ray binary pulsars during outburst

Date: 2015-07-09
Speaker: Prahlad R. Epili
Venue: Room # 113 (Thaltej Campus)

Abstract

Be/X-ray Binaries (BeXBs) are known to be a subgroup of high mass X-ray binaries. In these binaries, the compact object is generally a neutron star (pulsar) and the optical companion is known to be a Be star. These pulsars are undetectable in X-ray band during most of the times. Sudden enhancement in X-ray emission from these sources occurs and lasts for tens of days to a few months during which the pulsar becomes easily detectable with space based X-ray observatories. The neutron star in the BeXBs has moderately eccentric orbits (e ≥ 0.3). Hence during periastron passage, a sudden mass transfer onto the neutron star leads to an enhancement in X-ray flux (i.e. X-ray outbursts). BeXBs can have giant (type II) and normal (type I) outbursts in addition to long quiescence periods. Giant outbursts in these systems results in a transient increase in X-ray flux of about 10^3 - 10^4 times that at quiescence. The resultant luminosity reaches the Eddington luminosity for a neutron star, making the system the brightest in the X-ray sky. We have attempted to investigate the X-ray timing and spectral parameters of such a pulsar (i.e. KS 1947+300) during its giant outburst in 2013. The results of this work will be discussed along with the characteristics of Be X-ray binaries.

Peak Detector Designing and its Calibration

Date: 2015-07-03
Speaker: Abdulkaleem Khan
Venue: Room #114 (Thaltej campus)

Abstract

Properties of highly excited states in small molecules

Date: 2015-07-03
Speaker: Mr. Amrendra Pandey
Venue: Ground Floor Lecture Hall

Abstract

Electronic dynamics of the stable states are rather less-complex and have been quite successfully studied for many small as well as large molecular systems. On the other hand, nature of highly excited states which are often unstable is hard to investigate, thus not known comprehensively. Dynamics of large systems having many degrees of freedom is normally resulted in the intermixed kinematics, and consequently extremely hard to untangle. This restricts one to consider a systematic approach: to start from simple and small systems. By using excitations from many ionization schemes and comparing the dissociation processes in near-identical molecular systems, we have analyzed these states in order to probe their properties. I will discuss some of the results obtained from the analysis of dissociation dynamics of two diatomic molecules N2 and CO in electron- and photon-impact processes. Based of the study, few common features of their highly unstable electronic states that can be materialized will be presented.

Plausibility of low scale Left-Right symmetry

Date: 2015-07-03
Speaker: Prof. Urjit Yajnik
Venue: Room No. 469

Abstract

The smallness of neutrino masses raises the hopes of links to a high energy scale through the see-saw mechanism. However, the value of the higher mass scale can vary from the GUT scale down to the TeV scale. We explore the scenario that the higher scale is close to the TeV scale and possibly manifest at LHC or a future collider. It is shown that using mostly arguments of symmetry and the viability of standard cosmology provides sufficient constraints to determine how low the scale can be. This is realised specifically using a supersymmetric implementation of Left-Right symmetry. It shown in this case that leptogenesis always remains viable and places no restriction on the scale of symmetry breaking. It is shown that Gauge Mediated Symmetry Breaking may also be communicating L<-->R parity breaking.

Dissipative properties of hot and dense matter in excluded volume hadron resonance gas model

Date: 2015-07-02
Speaker: Guruprasad Prakash Kadam
Venue: Room No. 469

Abstract

Matter created in Relativistic Heavy Ion Collider i.e quark gluon plasma (QGP), is "the most perfect" fluid found in nature. Although "the most perfect fluid" implies zero viscosity, QGP has non zero shear viscosity(5 × 10^11 Pa·s). Indeed, based on anti-deSitter-conformal field theory (AdS/CFT) correspondence, Kovtun-Son-Starinets conjectured that no fluid found in nature can have shear viscosity to entropy ratio less that 0.08. This bound is famous KSS bound. However, in our recent work based on relativistic kinetic theory, we found that a simple system consisting of gas of hard spheres hadrons, KSS bound is violated if the gas is sufficiently dense. In this seminar I will discuss these results of the kinetic theory within the limitations of the theory.

Study of Comet C/2014 Q2 (Lovejoy)

Date: 2015-07-02
Speaker: Kumar Venkataramani, PRL
Venue: Room # 113 (Thaltej Campus)

Abstract

Comets are cold icy bodies in the solar system that were probably formed in the solar nebula and are considered to be the signature bodies to understand the formation of the solar system. As the comet nucleus makes its journey towards its parent star, the ices start sublimating giving rise to a mixture of gas and dust which forms the coma. The comet spectrum shows a continuum in the visible region at large heliocentric distances which is basically the solar radiation scattered by the cometary dust. In addition it exhibits strong molecular emission lines close to the perihelion. Comet C/2014 Q2(Lovejoy), an Oort cloud comet was discovered by Terry Lovejoy in August 2014. The spectra of this comet were obtained using the low resolution grating spectrograph (LISA) on the 0.5m telescope at the Mount Abu Infrared Observatory. LISA is a slit based spectrograph with a focal ratio of F/5 covering a wavelength range of 400-700 nm in the visible and 650 nm to 1 micron in the Near IR. The spectra showed very strong molecular emission lines close to its perihelion in late January 2015. Some of these emission lines, the extent of the dust continuum and their variation with heliocentric distance were studied. The results from this study will be presented in the talk.

Understanding the evolution of the Marwar basin: A geochemical perspective

Date: 2015-06-30
Speaker: Mr. Bivin Geo George
Venue: Ground Floor Lecture Hall

Abstract

The Late Neoproterozoic to Early Cambrian (750Ma- 500Ma) witnessed remarkable events in the Earth?s history such as the break-up of supercontinent Rodinia, evolution of multi-cellular life, an oxygenation event and the evolution of a climate system that is similar to the present day. These global events often leave their imprints in the contemporaneous sedimentary rocks. In the talk, I shall discuss some of the results from our study aimed at understanding the provenance, paleogeography and tectonic setting of the sedimentary rocks of the contemporaneous Marwar basin.

Study of variations in CO2, CH4 and CO at Ahmedabad

Date: 2015-06-29
Speaker: Naveen Chandra
Venue: Ground Floor Lecture Hall

Abstract

CO2 and CH4 are two most important long-lived greenhouse gases, which contribute more than 75% to the radiative forcing and hence influence climate. Both these gases have substantially increased due to anthropogenic emissions since the beginning of the industrial era. Although their effects on climate are well known, their regional budgets still show large uncertainties especially over South Asia. One of the major causes of these uncertainties is the lack of spatial and temporal atmospheric observations of these gases. An attempt has been made to study the variability of CO2, CH4 levels at Ahmedabad using a highly sensitive cavity ring down spectroscopy technique. I shall discuss some important results extracted from the yearlong observations of these gases during presentation.

Timing and Spectral Studies of Supergiant High Mass X-ray Binary Pulsars

Date: 2015-06-25
Speaker: Gaurava K. Jaisawal
Venue: Room # 113 (Thaltej Campus)

Abstract

X-ray binary pulsars with supergiant stars as companions generally show random and rapid variation in X-ray intensity. Unlike Be/X-ray binary pulsars, the supergiant X-ray binary pulsars rarely show X-ray outbursts of significantly enhanced luminosity. In case of several such binary pulsars, variation in X-ray intensity is observed at time scales of hundreds to thousands of seconds. Soft and hard X-ray light curves of these pulsars show the presence of several flare like episodes along with extended low intensity segments. We tried to investigate the properties of a few such pulsars such as OAO 1657-415, 4U 1700-37 during low and high flux levels by using observations from space based X-ray observatory Suzaku. Our results show that the occurrence of flares in the X-ray light curves can be explained by using clumpy stellar wind model. The results obtained from these works will be discussed in the talk.

In situ petrological evidence from ophiolite suggest that mantle upwelling in spreading center initiated from mantle transition zone (>410 - 660 km).

Date: 2015-06-23
Speaker: Dr. Souvik Das
Venue: Ground Floor Lecture Hall

Abstract

Ophiolites are generally considered as relics of spreading center. Geoscientists strongly believe that, spreading center rocks are derived from shallow upper mantle (<90 km). But geophysical studies have shown that the root of the mantle upwelling beneath a spreading centre is at much greater depths (>100 ? 410 km). To fill this knowledge gap present research has been carried out on mantle part of a well preserved Tethyan ophiolite (Nidar valley, SE Ladakh) along Indus Suture Zone. Finding of ultra high pressure minerals infer that some part of the Nidar ophiolite have evolved from the mantle transition zone.

Development of LabVIEW and NI-DAQ based Data acquisition

Date: 2015-06-19
Speaker: Dharak M. Patel
Venue: Room #114 (Thaltej campus)

Abstract

Weighing and reconstructing new physics mass and events at LHC

Date: 2015-06-18
Speaker: Abhay Kumar Swain
Venue: Room No. 469

Abstract

After successful discovery of the Higgs boson, the Large Hadron Collider (LHC) would confront the major challenge in searching for new physics and new particles. Any such observation necessitates the determination of mass and other quantum numbers like spin, polarisation etc. Many of our theories beyond the Standard Model (BSM) motivated from profound experimental indication of dark matter (DM), trying to accommodate them as some stable BSM particles within these theory. In such scenario, any production of heavy resonance of new particles eventually decay semi-invisibly resulting at least two stable particles in the final state. Reconstruction of these events at hadron colliders together with the mass determination of DM or intermediate particles is challenging and center to this talk. In this talk I will discuss some mass restricting way that can lead us to determine the new particle mass when it decays semi-invisibly. I will also present a new method which can be used for the full reconstruction of the event in the above scenario.

The spectral signature of stars

Date: 2015-06-18
Speaker: Ms. Priyanka Chaturvedi
Venue: Room # 113 (Thaltej Campus)

Abstract

The light that is emitted from the stellar photosphere consists of continua as well as absorption lines, which serves as a unique signature to help us decode the remarkable nature of stars. The behavior of these stellar absorption lines depend upon the surface temperature, mass, evolutionary status and chemical composition of the star. The study of stellar photosphere is a useful tool to connect our observations with other relevant parameters of interest. In the Radial Velocity technique, we determine the mass and radius of the secondary star (or a planet) as a function of the mass and radius of the primary host star. Thus, accurate determination of host star properties is important in proper estimation of mass and age of the companion. We, as a team of PARAS (Physical Research Laboratory Advanced Radial-velocity Abu-sky Search), have developed an indigenous package, PARAS-SPEC, to determine the stellar properties of the primary host star. It is an IDL based programming tool and based on the synthetic spectral fitting method and equivalent width method. The basic principles and methodology used for designing this tool will be discussed in the talk. A few results when applied to known and unknown stars shall be discussed along.

Decoding Crustal Evolution

Date: 2015-06-16
Speaker: Dr. Shrema Bhattacharya
Venue: Ground Floor Lecture Hall

Abstract

The Earth is thought to have been formed about 4.6 billion years ago from solar nebula. By the early igneous differentiation processes two types of crust have been generated, namely oceanic and continental. These crusts and upper mantle, which is known as lithosphere was broken up into number of tectonic plates. Oceanic crust reconcile the ages only up to 200 million year from today, in contrast continental crust are the oldest rocks on Earth formed during 3.7 to 4.6 billion years ago and provide the details of earth’s differentiation processes. New continental crust is mostly linked to the intense orogenic cycles of super continent formation such as, Rodinia, Pangea and Gondwana by the amalgamation of old micro-continents, their destruction and recycling. This talk will give a glimpse of the two orogenic cycles and how the continental crust formed using whole rock geochemistry, U-Pb isotope geochronometre and Lu-Hf Isotopic tracer in the mineral zircon.

Dust in Solar System

Date: 2015-06-12
Speaker: Dr. Jayesh Pabari
Venue: Room #114 (Thaltej campus)

Abstract

Dust in Solar System

Date: 2015-06-12
Speaker: Dr. Jayesh Pabari
Venue: Room #114 (Thaltej campus)

Abstract

New results from PARAS: Evidence of exo-planets around Giants

Date: 2015-06-11
Speaker: Dr. Abhijit Chakraborty
Venue: Room # 113 (Thaltej Campus)

Abstract

There are about 560 known exoplanets, which are as massive as Jupiter or bigger, and this is about one-third of the known population of exoplanets. Most of these exoplanets orbits around Sun-like dwarf stars. Despite large and diverse population of such Jupiters, only a handful of them are found around Giant stars (evolved stars, finished Hydrogen burning in their core) with an orbit of less than 0.5AU semi-major axis. Such evolved stars have typically radii of 2 to 10 solar radii and exoplanets in the close proximity usually gets destroyed due to very strong tidal interactions and heat and eventually gets engulfed. PARAS results show existence of a transiting Jupiter of mass 1.4 Jupiter mass and approximate period of 39 days around an evolved star of 1.5 Solar Mass (upper limit) with stellar radius of 2 to 4 solar radii. The planet has an orbital eccentricity of 0.05 and semi-major axis of 0.255 AU and measured K-value (semi-amplitude) of 65m/s. I will discuss about other prospective transiting candidates and also new results on tau Ceti a Radial-Velocity standard star showing unprecedented sub-1m/s precision as a future precursor of what can be achieved using the new PRL 2.5m telescope.

Influence of solar activity on rainfall-indications from speleothems

Date: 2015-06-09
Speaker: Dr. M. G. yadava
Venue: Ground Floor Lecture Hall

Abstract

High-resolution proxy based rainfall records show that there are rhythmic changes which shall be attributed to solar activity. Interestingly, the rhythmicity is not persistent; it appears for a certain period of time as observed in two speleothems studied so far. Some plausible explanations on a physical link between sun and Indian monsoon will be discussed.

Noble gases in Howardites and First, preliminary results of noble gases from minerals of Lohawat howardite using Noblesse and Laser microprobe

Date: 2015-06-05
Speaker: Ramakant R. Mahajan
Venue: Room #114 (Thaltej campus)

Abstract

Vesta-HED Connection: A post DAWN view

Date: 2015-05-29
Speaker: Dr. S.V.S. MURTY
Venue: Room #114 (Thaltej campus)

Abstract

Vesta-HED Connection: A post DAWN view

Date: 2015-05-29
Speaker: Dr. S.V.S. MURTY
Venue: Room #114 (Thaltej campus)

Abstract

Application of Accelerator Mass Spectrometry (AMS) in study of Cosmogenic Isotopes

Date: 2015-05-26
Speaker: Dr. Ravi Bhushan
Venue: Ground Floor Lecture Hall

Abstract

Accelerator Mass Spectrometry (AMS) is an advanced ultrasensitive mass spectrometry technique for measurement of cosmogenic radionuclides in extremely small quantity of samples with a much reduced analysis time. The advent of AMS not only facilitated orders of magnitude lower requirement of sample quantity and analysis time, but also opened new avenues of research in earth sciences. The low energy (MeV) Accelerator Mass Spectrometer (AMS) being procured by PRL is a universal compact AMS which can effectively measure several cosmogenic radionuclides that include 14C, 10Be and 26Al. AMS has found extended application in archaeology, oceanography, hydrology, geology, biomedical research and paleoclimatology. AMS would not only provide new opportunities in application of cosmogenic isotopes in earth, atmosphere and planetary sciences, but would also serve as a long lasting requirement for a geochronological facility.In this talk, some applications of AMS in earth sciences would be discussed.

From double-slit interference to structural information in simple hydrocarbons

Date: 2015-05-26
Speaker: Dr. R.K. Kushawaha
Venue: Room No. 469

Abstract

Interferences in coherent emission of photoelectrons from two equivalent atomic centers in a molecule are the microscopic analogous of the celebrated Young's double-slit experiment. By considering inner-valence shell ionization in the series of simple hydrocarbons C2H2, C2H4 and C2H6, we show that double-slit interference is widespread, and has built-in quantitative information on geometry, orbital composition and many-body effects. A theoretical and experimental study is presented over the photon energy range 70-700 eV. A strong dependence of the oscillation period upon the C-C distance is observed, which can be used to determine bond lengths between selected pairs of equivalent atoms with at least 0.01 Å accuracy. Furthermore, we show that the observed oscillations are directly informative of the nature and atomic composition of the inner-valence molecular orbitals, and observed ratios are quantitative measure of elusive many-body effects. The technique and analysis can be immediately extended to a large class of compounds.

Martian "Blueberries": Implications and terrestrial analogy

Date: 2015-05-22
Speaker: Dr. Dwijesh Ray
Venue: Room #114 (Thaltej campus)

Abstract

Martian "Blueberries": Implications and terrestrial analogy

Date: 2015-05-22
Speaker: Dr. Dwijesh Ray
Venue: Room #114 (Thaltej campus)

Abstract

Speckle imaging with masked apertures: application to solar imaging

Date: 2015-05-20
Speaker: Dr. R. Sridharan
Venue: USO Seminar Hall

Abstract

COMPTON-BELKOVICH VOLCANIC COMPLEX (CBVC): An Ash Flow Caldera on the MOON

Date: 2015-05-15
Speaker: Mamta Chauhan
Venue: Room #114 (Thaltej campus)

Abstract

The presentation will cover the aspects related to planetary volcanism with silicic volcanism in general, lunar volcanism, redspots, uniqueness of CBVC with discussions particularly focused on the following subjects: ? Detailed morphological and structural appraisal of various volcanic features at CBVC as observed through high-resolution optical data and inferred from radar interpretation supported by their topographical analysis and their description based on based on experimental as well as field based study of terrestrial calderas by various researchers. ? Evidence of pyroclasts in the form of coarse and fine ash flow observed through radar and high-resolution optical imagery. ? Role of regional tectonics and local stresses generation in evolution of area and control of Pre-caldera topography on the shape of the CBVC caldera. ? Proposed model for caldera evolution in the CBVC area based on the various observations recorded in the area, morphology and trend of the various features, regional geology and basic caldera formation stages in terrestrial conditions. ? The various petrological implications associated with prolonged silicic magmatic activity in the area, the episodic events associated with silicic magmatism will be discussed. ? In addition a thorough discussion on the presence of strong endogenic hydroxyl anomaly reported in the area, its difference from the other lunar silicic areas and its role played in geological and morphological evolution of the area will be touched upon.

Determination of Hubble constant (H_0) through monitoring of gravitationally lensed quasars

Date: 2015-05-14
Speaker: Dr. S. Rathnakumar
Venue: Room # 113 (Thaltej Campus)

Abstract

The Hubble constant at the present epoch ($H_0$) is an important cosmological parameter on which all extragalactic distances depend. Multiple approaches need to be pursued to constrain its value in order to be able to identify and eliminate unknown systematic errors present in any one approach. Strong gravitational lensing offers one method to constrain $H_0$ free from calibrations associated with standard candles. It is based on (i) measuring the time delay(s) between the multiple images of a cosmologically distant variable source which is strongly lensed by a galaxy or galaxy cluster that lies in close proximity to its line-of-sight and (ii) modelling the mass distribution of the deflector. We have carried out photometric monitoring of a sample of six gravitationally lensed quasars using the 2-m Himalayan Chandra Telescope (HCT) as part of the COSmological MOnitoring of GRAvItational Lenses (COSMOGRAIL) campaign to measure time delays of most known lensed quasars in both hemispheres using a network of medium-size telescopes. I will discuss in detail our results of this campaign, using a newly devised "difference-smoothing" technique to measure time delay and pixellated modelling of the mass distribution of the deflector to constrain the $H_0$ value.

Characterization of secondary organic aerosols present in the ambient atmosphere

Date: 2015-05-12
Speaker: Mr. Satish R. V.
Venue: Ground Floor Lecture Hall

Abstract

Aerosols are of central importance for atmospheric chemistry and physics, biosphere, climate, and public health. Organic aerosols (OA) constitute about half of the total sub-micrometer particulate mass in the troposphere. These OA can be emitted to the atmosphere directly as particles (primary OA, POA) and/or formed in the atmosphere through oxidation of volatile organic carbon (secondary OA, SOA). Evidences suggest that SOA is often dominant component of OA, and majority of SOA is water soluble. Some of the water-soluble organic aerosols (known as brown carbon) absorb sunlight, which causes additional direct/indirect climatic effects of OA. In this talk, various characteristics of ambient SOA will be discussed.

The Silicon Photomultiplier (SiPM)- Its Readout & Application

Date: 2015-05-08
Speaker: Rishabh Shukla
Venue: Room #114 (Thaltej campus)

Abstract

In this talk, working of SiPM as photon detector will be discussed along with the design and development of Charge sensitive Pre-Amplifier(CSPA) and Gaussian Pulse Shaping circuit. Applications of SiPM, such as position sensing and in spectroscopy will be also be discussed.

The Silicon Photomultiplier (SiPM)- Its Readout & Application

Date: 2015-05-08
Speaker: Rishabh Shukla
Venue: Room #114 (Thaltej campus)

Abstract

Microbial cycling of nitrogen in agriculture: Great acceleration and its impacts

Date: 2015-05-05
Speaker: Dr. B. Ramakrishnan
Venue: Ground Floor Lecture Hall

Abstract

Gauge mediated supersymmetry breaking in the light of HIggs

Date: 2015-05-05
Speaker: V Suryanarayana Mummidi
Venue: Room No. 469

Abstract

In this talk, I review aspects of Minimal Gauge mediated supersymmetry breaking models and discuss its phenomenological status in the light of much celebrated discovery of CP even Higgs scalar at the LHC. I present few viable extensions of mGMSB models in the context of supersymmetry breaking.

Suppression of phase separation in warm condensate mixtures

Date: 2015-04-30
Speaker: Mr. Arko Roy
Venue: Room No. 469

Abstract

We shall discuss about the role of thermal fluctuations in binary condensate mixtures of dilute atomic gases. We use Hartree-Fock-Bogoliubov with Popov approximation to probe the impact of non-condensate atoms to the phenomenon of phase-separation in two-component Bose-Einstein condensates. We demonstrate that, in comparison to $T=0$, there is a suppression in the phase-separation of the binary condensates at $T\neq0$. This arises from the interaction of the condensate atoms with the thermal cloud. We also show that, when $T\neq0$ it is possible to distinguish the phase-separated case from miscible from the trends in the correlation function. However, this is not the case at $T=0$.

"Presentations by First Year Students"

Date: 2015-04-28
Speaker: Ms. Niharika Sharma; Mr. Wriju Chowdhury; Mr. Raghwendra N. Shandilya; Mr. Sachin Gupta; Mr. Anil Patel; Mr. P. Kiran Kumar
Venue: Ground Floor Lecture Hall

Abstract

Magnetospheric substorms and its implications

Date: 2015-04-27
Speaker: Dr. Dibyendu Chakrabarty
Venue: Ground Floor Lecture Hall

Abstract

A few decades back, magnetospheric substorms used to be thought as building blocks of a geomagnetic storm. With the dawn of space age, this notion was shown to be incorrect. Substorms have characteristic features that are quite different from a storm although solar wind parameters (that drive storms) can have roles in triggering substorms. Identifying the triggering mechanisms of substorms, understanding its spatio-temporal evolution, its relationship with storm and its impact over low latitude ionosphere and thermosphere are a few challenging research issues that have been receiving global attention. A few of these aspects will be discussed.

Ions in water: Implications to safe water, food and environment

Date: 2015-04-23
Speaker: Dr. T. Pradeep
Venue: Ground Floor Lecture Hall

Abstract

Clumped isotopes in air CO2 and carbonates: implications to global carbon cycle and paleoclimate studies

Date: 2015-04-21
Speaker: Dr. A. H. Laskar
Venue: Ground Floor Lecture Hall

Abstract

Molecules containing two rare isotopes (e.g. 13C18O16O in CO2),called clumped isotopes are powerful tools to independently constrain the sources of CO2 in the atmosphere and paleo temperature reconstruction. This is due to their unique physical and chemical properties such as the abundance of 13C-18O bond is purely temperature dependent and is independent of the oxygen isotopic composition of parent material unlike oxygen isotope thermometry in which oxygen isotopic composition of original water must be known for any kind of paleoclimate study. In this talk I will briefly discuss the principles and applications of clumped isotopes in CO2. I will also present our recent results on identifying sources of CO2 in the atmosphere, quantifying anthropogenic fractions of CO2 in urban and industrial areas, paleo temperature reconstruction using various carbonate archives and endothermic/ectothermic thermoregulations of dinosaurs using clumped isotopes. Also I will discuss some advanced applications and future prospects of clumped isotopes.

Introduction to Genetic Algorithm

Date: 2015-04-20
Speaker: Dr. Y. B. Acharya
Venue: Ground Floor Lecture Hall

Abstract

Genetic algorithms are one of the best ways to solve a problem for which little is known. This method finds solutions to an optimization problem that takes advantage of evolutionary principles; different possible solutions to the problem are iteratively subjected to replication, mutation and selection processes. In the talk, I will discuss some of these.

Geophysical parameter retrieval from hyperspectral sounding over tropical region

Date: 2015-04-13
Speaker: Dr. Jagat Singh Bisht
Venue: Ground Floor Lecture Hall

Abstract

The retrieval of vertical profiles of geophysical parameters is very important for various atmospheric applications such as weather monitoring, climate applications and as an input in numerical weather prediction models. The last decade has witnessed the evolution of advanced infrared hyperspectral sounders such as Aqua-Atmospheric Infrared Sounder(AIRS), MetOp-Infrared Atmospheric Sounding Interferometer(IASI), and Suomi NPP-Cross-track Infrared Sounder(CrIS) which contain very high spectral and vertical resolution. In this talk, I will present an improved scheme for the geophysical parameter retrievals and its application potential over tropical atmosphere.

Model of multi magnetic flux tube configurations in the Lower Solar Atmosphere

Date: 2015-04-10
Speaker: Dr. Viktor Fedun
Venue: Room No. 469

Abstract

In this talk we will show the possibility of analytical construction of realistic magnetic field configurations, typical of the lower solar atmosphere. The magneto-hydrostatic equilibrium is obtained by taking into account the presence of external forces. Systems incorporating open single and multiple flux tubes and closed magnetic loops can be combined to form magnetic structures that could even represent complex solar active regions. The developed model successfully spans the Interface Region of the solar atmosphere, from the photosphere up to the solar corona across the challenging transition region, while retaining physically valid plasma pressure, density and magnetic flux. Modelling magnetic structures can depict the main characteristics of solar intergranular lanes or active regions. HMI data can be used, as an initial magnetic field distribution, to construct a realistic magnetic field distribution. The model includes a number of free parameters, which makes the solution applicable to a variety of other physical problems, and it may therefore be of more general interest.

Degree of differentiation in planetary objects

Date: 2015-04-10
Speaker: Dr. Amit Basu Sarbadhikari
Venue: Room #114 (Thaltej campus)

Abstract

Degree of differentiation in planetary objects

Date: 2015-04-10
Speaker: Dr. Amit Basu Sarbadhikari
Venue: Room #114 (Thaltej campus)

Abstract

Properties, simulations, and results of perovskite materials at finite temperatures

Date: 2015-04-09
Speaker: Dr. Brajesh K. Mani
Venue: Room No. 469

Abstract

Perovskite materials are of considerable interest both fundamentally as well as for their potential technological applications reasons. One of the many great fascinating properties of these materials is that they can display a variety of structural phase transitions, such as ferroelectric, ferromagnetic, antiferrodistortive, antiferroelectric, antiferromagnetic, and in some cases a combination of two or even more of these. An accurate prediction and comparison of these properties with experiments requires estimation at finite temperatures, but is beyond the scope of density functional theory. An approach based on a microscopic effective Hamiltonian makes these studies possible. The parameters in the effective Hamiltonian are determined from first-principles calculations and used in the framework of Molecular Dynamics and/or Monte Carlo simulations. In this seminar, after providing a brief introduction to the simulation methods, I will discuss our simulation results and their technological importance for ferroelectric PbTiO3, antiferroelectric PbZrO3, and multiferroic BiFeO3 materials.

Lately Exposed Amorphous Water Ice on Comet 49P/Arend-Rigaux

Date: 2015-04-06
Speaker: Dr. Bhalamurugan Sivaraman
Venue: Ground Floor Lecture Hall

Abstract

Comet 49P/ Arend-Rigaux, thought to be a low activity comet since the 1980?s was found to be active in its recent apparitions. Recent analysis of the data obtained from Spitzer observation of the comet in 2006 compared with laboratory spectra had revealed amorphous water ice on the surface. In addition, in 2012 a jet was found to appear during its subsequent perihelion passage as witnessed during an observation carried out (By Shashikiran, A&A) on 26th March 2012 using the PRL telescope at Mt. Abu. This confirms recent activity of Comet 49P/Arend-Rigaux due to the volatile subsurface materials exposed after several passages close to the Sun. Our result confirms the subsurface ices on cometary nuclei and insists for more observations for a better understanding.

Biochemical modeling of tree ring cellulose isotope data for Paleo-reconstructions.

Date: 2015-03-31
Speaker: Dr. Trina Bose
Venue: Ground Floor Lecture Hall

Abstract

One of the primary sources of climatic variability information in recent past are the tree ring cellulose isotope datasets due to their stable temporal resolution. However the reconstructions produced from such data have variable dependabilities due to their site and species specificness in terms of parameter reconstructed and the calibration correlation. Cellulose formation in all of the trees (including the ring bearing ones) is mostly the same basic physiochemical process as they all undergo C3 metabolic process.This process and resultant isotopic fractionation have been modeled from experimental information on live trees. In presence of basic meteorological data i.e. temperature and humidity estimates, pCO2 has been reconstructed from carbon isotope data from tree ring cellulose.The processes involving oxygen and hydrogen isotope fractionations provide information about humidity, temperature and source water isotopic compositions. Some of these process based reconstruction models will be discussed.

Facilities to probe the Earth's middle and upper atmosphere using Rockets

Date: 2015-03-30
Speaker: Shri. Pramod Kumar Pandey
Venue: Ground Floor Lecture Hall

Abstract

ATV Project, VSSC offers a variety of Sounding rockets for the Scientific exploration of middle and upper atmosphere. Some of the rockets can be launched from Thumba near to geomagnetic equator and others from Sathish Dhavan Space Centre, Sriharikota. The talk cover the specifications of various sounding rockets, facilities offered to Scientists, Telemetry, tracking and command functions that can be made use of by Scientists. The talk also covers briefly the instrumentation and support systems that can be offered to Scientists

THE GRAND CHALLENGES IN EARTH SURFACE PROCESS STUDIES WITH ILLUSTRATIONS FROM FLOOD STUDIES

Date: 2015-03-24
Speaker: Prof. R. J. Wasson
Venue: PRL GUEST HOUSE

Abstract

The grand challenges (according to the National Research Council of the USA, 2010) are: 1. Interacting Landscapes and Climate 2. Quantitative Reconstruction of Landscape Dynamics Across Time Scales 3. The coevolution of Ecosystems and Landscapes 4. The Future of Landscapes in the ?Anthropocene? These challenges should involve geoscientists, ecologists, atmospheric scientists, physicists, chemists, mathematicians, historians, social scientists, and engineers. Each of these grand challenges will be illustrated using the reconstruction of flood histories from India and Thailand.

Photography, Yesterday and Today

Date: 2015-03-23
Speaker: Shri. R. N. Misra
Venue: Ground Floor Lecture Hall

Abstract

Photography has enjoyed an important place in the field of scientific data acquisition. Photosensitive materials have been used for long term data storage, and photographic equipment modified to suit scientific requirements. The rapid development in solid state technology has resulted in wide availability of low cost CCD and CMOS image sensors, along with enormous data processing power in very small volume. The field of photography has, consequently, changed drastically in the past two decades, and many of the design parameters need a fresh look. I will give a brief overview of historical aspects and some of the recent developments.

A new technique for measuring the leakage current in Silicon Drift Detector based X-ray spectrometer ? implications for on-board calibration

Date: 2015-03-20
Speaker: M Shanmugam
Venue: Room #114 (Thaltej campus)

Abstract

A new technique for measuring the leakage current in Silicon Drift Detector based X-ray spectrometer ? implications for on-board calibration

Date: 2015-03-20
Speaker: Mr. M Shanmugam
Venue: Room #114 (Thaltej campus)

Abstract

Heavy Ion Physics - basics and some recent results

Date: 2015-03-19
Speaker: Prof. Sourendu Gupta
Venue: Room No. 469

Abstract

-NA-

Multi-elemental and Isotopic (87Sr/86Sr) Characterization and Authentication of the Indian Basmati Rice

Date: 2015-03-17
Speaker: Dr. Rupali Anant Lagad
Venue: Ground Floor Lecture Hall

Abstract

Globalization of agricultural products has increased risk of adulteration of premium quality food products. In order to protect loyal producers and consumer’s right for safe and healthy food, Geographical Indication (GI) is an effective activity, which is developed especially for protecting the geographical authenticity of food stuffs. Multi-elemental profiling, REEs pattern, isotopic composition of food plays important role in checking quality, safety and authenticity of GI protected food stuff. In the present research work, globally demanded, premium cost, Indian GIs protected agricultural product, authentic Basmati rice samples were analyzed for its multi-elemental profiling and 87Sr/86Sr ratio fingerprinting. The results obtained for same will be discussed in the seminar.

Space Based Radar Altimetry technique to look at Rainfall over the Global Oceans

Date: 2015-03-16
Speaker: Prof. Satyendra M. Bhandari
Venue: Ground Floor Lecture Hall

Abstract

Over the last more than 30 years Radar Altimtery from Space has provided 'Oceanographers' with a new tool to look at a variety of phenomena and processes going on in different parts of the global oceans. Radar Altimetry has truly revolutionized the subject Physical Oceanography and many other areas of Geosciences and it is constantly innovating itself to add new dimensions.In the present talk, however, I will attempt to describe a 'new' unanticipated application of Radar Altimetry from space - towards detection and estimation of rainfall over the global oceans. This is an 'atmospheric' application of the primarily 'oceanographic' radar altimetric missions. By making an innovative use of 'differential attenuation' that the dual-frequency (C vs. Ku Bands) radar altimetric signals suffer during their two-way passage through the raining atmosphere - we were able to detect and study rainfall over global oceans. Besides providing a new alternative to measure and map global rainfall for many applications including the global hydrological cycle, delineating its presence is also essential to tag and remove rain corrupted oceanic measurements made by the altimeters. Radar Altimetry from space is highly fascinating in that it is based on the simplest concept of measuring distance by reckoning the E.M. travel time between the transmitted and returned radar pulse. However it successful implementation required tremendous sophistication to be able to deliver the required precision and accuracy needed to address useful Oceanographic applications. After providing the general background of the concepts involved in space based radar altimetry, the talk would describe the development of rainfall estimation technique and present the global rainfall maps generated using this technique.

Long term records of the Indian monsoon as revealed by 3 recent papers

Date: 2015-03-10
Speaker: Prof. R. Ramesh
Venue: Ground Floor Lecture Hall

Abstract

Three recent papers have tried to reconstruct the Indian monsoon on various timescales and with different resolutions. The first, concentrates on the last two millennia (from north India), the second the last glacial period (south India), and the third (China) covers the full glacial interglacial cycle. In this seminar I will present these papers and discuss their relative merits and demerits. I will also highlight our continuing efforts to fill gaps in the Holocene monsoon records and show how recent ocean records verify our earlier conclusions.

Volatile Organic Compounds in the Atmosphere: Results from PTR-TOF-MS Measurements at Ahmedabad

Date: 2015-03-09
Speaker: Dr. Lokesh Sahu
Venue: Ground Floor Lecture Hall

Abstract

Volatile organic compounds (VOCs) are ubiquitous atmospheric constituents of both anthropogenic and natural origins. VOCs are important precursors of tropospheric ozone and secondary organic aerosols (SOA) which can impact air quality and global climate. Most of the primary VOCs and their oxidized products make major fraction of secondary pollutants in urban regions. The VOCs control the oxidizing capacity of the global troposphere mainly due to the fast reactions with hydroxyl (OH) radical. Gas chromatograph (GC) with flame ionization detector (FID) and mass spectrometer (MS) have been widely used for the analysis of VOCs. However, measurements of many reactive VOCs are not possible using GC based techniques. In PRL, we are using a fast response proton transfer reaction time of flight mass spectrometer (PTR-TOF-MS) for the real time detection of a wide spectrum of VOCs in air. The PTR-TOF-MS based measurements are particularly important to understand the role of photochemical process and biogenic emissions. A brief summary of VOCs and results obtained from the PTR-TOF-MS measurements at Ahmedabad during winter season will be presented.

Seasonality in Secondary Aerosol Formation over the Indo-Gangetic Plain

Date: 2015-03-03
Speaker: Dr. Neeraj Rastogi
Venue: Ground Floor Lecture Hall

Abstract

Understanding the secondary aerosol formation is among most important topics in the field of aerosol research because its poor understanding leads to large uncertainty in the assessment of aerosol effects on air quality and climate. The Indo-Gangetic Plain (IGP) receives large amount of primary particles and precursors of secondary particles from the emissions from vehicles, industries, thermal power plants, large-scale post-harvest biomass burning, and bio-fuel burning; however, knowledge on secondary aerosol abundances and characteristics is sparse. Based on the year-round day and night time sampling of atmospheric fine particles from Patiala, this talk will discuss the temporal characteristics of primary and secondary aerosols over the IGP, and their implications. The importance of time resolved measurements in understanding the secondary aerosol formation processes will also be discussed.

Enhancements and Losses of Radiation Belt Particles: Van Allen Probes Observations

Date: 2015-02-27
Speaker: Prof. Daniel N. Baker
Venue: Ground Floor Lecture Hall

Abstract

The dual-spacecraft Van Allen Probes mission has provided a new window into megaelectron Volt (MeV) particle dynamics in the Earth's radiation belts. Observations (up to E ~10 MeV) show clearly the behavior of the outer electron radiation belt at different time scales: months-long periods of gradual inward radial diffusive transport and weak loss being punctuated by dramatic flux changes driven by strong solar wind transient events. Analysis of multi-MeV electron flux and phase space density (PSD) changes during March 2013 are presented in the context of the first year of Van Allen Probes operation. This March period demonstrates the classic signatures both of inward radial diffusive energization as well as abrupt localized acceleration deep within the outer Van Allen zone (L ~4.0±0.5). This reveals graphically that both "competing" mechanisms of multi-MeV electron energization are at play in the radiation belts, often acting almost concurrently or at least in very rapid succession. It also shows in remarkable ways how the coldest plasmas in the magnetosphere intimately control the most highly energetic particles.

Latitude Dependent Mantle (LDM) of Mars

Date: 2015-02-27
Speaker: Mr. Rishitosh K Sinha
Venue: Room #114 (Thaltej campus)

Abstract

Latitude Dependent Mantle (LDM) of Mars

Date: 2015-02-27
Speaker: Mr. Rishitosh K Sinha
Venue: Room #114 (Thaltej campus)

Abstract

Space Plasma Waves and "Turbulence" from an Observational Point of View

Date: 2015-02-26
Speaker: Dr. Bruce Tsurutani
Venue: Ground Floor Lecture Hall

Abstract

I will show examples of plasma waves and the beginning of turbulence from a space plasma (spacecraft) point of view. Magnetospheric chorus, cometary waves and interplanetary Alfven waves will discussed in detail. At least at the initial stages, the turbulence associated with different wave modes are distinct from each other.

Particles and fields in the solar system

Date: 2015-02-23
Speaker: Prof. Daniel N. Baker
Venue: USO Seminar Hall

Abstract

Even before the official dawn of the Space Age – that is, the launch of the Sputnik and Explorer spacecraft in 1957-1958 – many investigators around the world were engaged in space physics research. Using rockets to get to the fringes of outer space, early researchers made pioneering observations of the Sun and Earth’s upper atmosphere. This talk will recount some of the earlier history of contributions to Sun-Earth (“solar terrestrial”) studies. A principal focus of the talk will be the modern studies of energetic particles and electromagnetic fields in Earth’s cosmic neighbourhood. From a rather personal perspective, my Laboratory for Atmospheric and Space Physics (LASP) has been playing an increasingly prominent role in forefront studies of Earth’s “magnetosphere” and LASP researchers are using this core terrestrial knowledge to advance planetary and astrophysical understanding as well. Moreover, study and understanding of the space environment of Earth is absolutely essential for our knowledge of “space weather” which represents a major threat to our modern technological society. The presentation will address all these aspects and will conclude with a look forward to future solar system programs and opportunities.

Airglow on the Earth and Mars: Modelling and Observations

Date: 2015-02-23
Speaker: Dr. P. Thirupathaiah
Venue: Ground Floor Lecture Hall

Abstract

Critical Mass of Neutron Stars: A Black Hole Entropic View

Date: 2015-02-20
Speaker: Prof. Parthasarathi Majumdar
Venue: Room No. 469

Abstract

We begin with a brief summary of extant approaches to understand the observed absence of neutron stars heavier than 2 solar masses. Many of these involve an adaptation of Chandrasekhar?s ideas of a limiting mass for white dwarf stars, based on hydrostatic equilibrium, to situations where general relativity can no longer be ignored. We survey the complications that this might introduce to the already difficult problem of determining the equation of state of this superdense system as an essential part of hydrostatic equilibrium. We then describe an alternative perspective, still under construction, to this problem, based on certain results from the analysis of (quantum) black hole entropy and thermal stability. These results, derived from a non-perturbative, background-independent formulation of canonical quantum gravity, will be discussed in some detail. Some attempts to incorporate entanglement entropy ideas into the construction are also to be discussed. The aim here is a formulation of the issue of neutron star instability in terms of the stability and growth of a nascent quantum horizon deep inside a collapsing neutron star. If this perspective works, this might be a first indirect evidence of quantum gravity playing an important role in the gravitational collapse of neutron stars.

METEORITE IMPACT CRATERS: IDENTIFICATION, IMPORTANCE AND ECONOMIC POTENTIAL. SOME CASE HISTORIES

Date: 2015-02-20
Speaker: Dr. M S Sisodia
Venue: Room #114 (Thaltej campus)

Abstract

METEORITE IMPACT CRATERS: IDENTIFICATION, IMPORTANCE AND ECONOMIC POTENTIAL. SOME CASE HISTORIES

Date: 2015-02-20
Speaker: Dr. M S Sisodia
Venue: Room #114 (Thaltej campus)

Abstract

146Sm-142Nd systematics in some Indian carbonatites and alkaline rocks: challenges and observations

Date: 2015-02-17
Speaker: Ms. Ikshu Gautam
Venue: Ground Floor Lecture Hall

Abstract

Geochemical and isotopic studies of Sm-Nd have contributed significantly to our knowledge of evolution of Earth?s mantle. Whereas the conventional isotopic system of these elements (147Sm-143Nd, t1/2=103Ga) is key to our understanding of evolution of the mantle over the geologic time, the short-lived 146Sm-142 Nd (t1/2=68 Ma) systematics helps us to zoom into the early history of evolution of the silicate Earth. The latter though requires high-precision mass spectrometry (< 10 ppm precision in 142 Nd/144Nd measurements), which became available only recently. In my talk I shall briefly discuss analytical challenges in 142 Nd/144Nd measurements, our efforts/progress in this direction, and preliminary results from some carbonatites and alkaline rocks of India ? aimed at locating the early enriched mantle reservoir.

Study of Thermal Emission on Mars: Preliminary Model Results

Date: 2015-02-16
Speaker: Mr. Masoom Jethwa
Venue: Ground Floor Lecture Hall

Abstract

Thermal Inertia for Martian Surface

Date: 2015-02-13
Speaker: Dr. Subhadyouti Bose

Abstract

Lessons learnt from Herschel Gould Belt Survey Key project observations

Date: 2015-02-12
Speaker: Dr. Arabindo Roy
Venue: Room # 113 (Thaltej Campus)

Abstract

In this talk I will present two key results from the Herschel Gould Belt Survey (HGBS) -- 1) constrain on the submillimeter dust opacity and 2) the importance of filamentary structures in connection with prestellar core formation. Thermal dust emission is optically thin at sub-mm wavelengths and thus it is often used as a proxy of matter. The conversion of dust emission to dust mass depends on the adoption of the value of dust opacity. Although dust properties in the diffuse medium is relatively well understood, however, in the dense medium it is very poorly constrained. Theoretically, dust grains are expected to evolve in dense medium by accreting ice mantles and accumulating metals. Using dust continuum emission and near infrared extinction data we show an evidence for non-linear evolution of dust opacity in the moderately dense medium as a function of column density, suggestive of grain growth. For high column density (Av>20 mag), however, taking account of line of sight temperature variation is crucial for accurate deciphering of dust properties. We used Abel's integral transform on the B68 globule to disentangle temperature variation and compared dust opacity therein. This method also yielded sucessful results for the reconstruction of volume density and dust temperature structures. HGBS observations have demonstrated the importance of filamentary structures in connection with core formation. The interstelar MHD turbulence creates an ubiquitous network of filaments. Herschel has resolved these structures in the nearby molecular cloud and found that they maintain a constant inner-width of 0.1 pc irrespective of their stability state. Thermally supercritical filaments (M_line > 2c_s^2/G) harbor most of the prestellar cores and the derived core mass function (CMF) suggested that peak of the CMF corresponds to the Jeans mass of gravitationally unstable filaments, however, the origin of Salpeter like power-law slope towards high mass end was unclear. I will also discuss that the longitudinal perturbation modes seeded by Kolomogorov turbulence may explain the power-law part of the CMF.

Geochemistry of continental shelf waters and sediments, south east coast of India, Bay of Bengal.

Date: 2015-02-10
Speaker: Dr. Nisha V.
Venue: Ground Floor Lecture Hall

Abstract

Continental shelf studies are important in order to understand the physico-chemical properties of sea water as well as biogeochemical systems existing in the marine environment. Lying within the tropical zone the east coast India receives strong monsoonal rains and hence any variation in the intensity and amount of precipitation would reflect in the seawater and sediment deposition characteristics along the continental shelf. This study quantifies the spatial and vertical heterogeneity in the distribution of seawater properties and geochemical parameters that influence their distributional trends in seafloor sediments during the 2009 post North East (NE) and South West (SW) monsoon periods along the east coast Tamilnadu continental shelf. In this talk, I would present some of the results on the distribution and monsoonal fluctuations of various physico-chemical and geochemical parameters of seawater and seafloor sediments spatially and vertically along the continental shelf East Coast Tamilnadu.

Study of the Ionosphere of Mars: Preliminary Model Results

Date: 2015-02-09
Speaker: Ms. Siddhi Shah
Venue: Ground Floor Lecture Hall

Abstract

Crater chronology: Moon to Mars and some recent results

Date: 2015-02-06
Speaker: S Vijayan
Venue: Room #114 (Thaltej campus)

Abstract

Quantum state discrimination by LOCC (local operations and classical communication)

Date: 2015-02-05
Speaker: Dr. Som S. Bandyopadhyay
Venue: Room No. 469

Abstract

Suppose a composite quantum system is known to be in one of many states, not necessarily orthogonal, such that its parts are distributed among spatially separated observers. The goal is to learn about the state of the system using only local quantum operations and classical communication between the parties (LOCC). This problem, known as local state discrimination, is of considerable interest, as in many instances the information obtainable by LOCC is strictly less than that achieved with global measurements even when the states are mutually orthogonal. Thus the problem of local state discrimination serves to explore fundamental questions related to local access of global information and the relationship between entanglement and local distinguishability. In this talk I will present a self contained review of local state discrimination along with some recent results.

Oxygenation of Earth's atmosphere-ocean system

Date: 2015-02-03
Speaker: Prof. J. S. Ray
Venue: Ground Floor Lecture Hall

Abstract

We take our oxygenated world for granted and expect to find breathable oxygen everywhere - after all, O2 makes up 21% of the modern atmosphere. However, free oxygen, at levels mostly less than 0.001% of that of present atmosphere, was anything but plentiful during the first half of Earth?s 4.5-billion-year history. Its rise to modern levels and impact on early biological evolution is one of the most interesting stories in Earth?s history. In this talk, I shall review the current status and discuss new methods of research on the topic

Science and Exploration of Mars Missions

Date: 2015-02-02
Speaker: Prof. S. A. Haider
Venue: Ground Floor Lecture Hall

Abstract

The MENCA experiment aboard the Mars Orbiter Mission

Date: 2015-01-30
Speaker: Dr. T. P. Das
Venue: Ground Floor Lecture Hall

Abstract

What controls the atmospheric abundances of dicarboxylic acids over the open ocean: Insights from the Western North Pacific

Date: 2015-01-29
Speaker: Dr. Bikkina Srinivas
Venue: Ground Floor Lecture Hall

Abstract

Atmospheric dicarboxylic acids (DCA), a ubiquitous and important component of secondary organic aerosols (SOA), play a crucial role in cloud condensation nuclei activity of aerosols, affecting the Earth’s climate. Despite the high abundances of oxalic acid and other DCA in the marine boundary layer, there is no consensus on what controls their atmospheric distributions over the open ocean. Although it is hypothesized that marine biological productivity is responsible for the production of DCA in the remote marine atmosphere, there were no substantial evidences to support the hypothesis based on field observations. Here, we present the unequivocal evidence for the marine source of DCA and related polar compounds whose concentrations showed several times higher in more biologically influenced aerosols (MBA) than in less biologically influenced aerosols (LBA). Their main sources are proposed as isoprene and unsaturated fatty acids emitted from the ocean surface during high biological activity as inferred by high abundances of isoprene-SOA tracers and azelaic acid. The measured concentrations of isoprene-SOA tracers in MBA show ca. 40 times higher than in LBA. These results demonstrate that marine derived isoprene and unsaturated fatty acids control the spatial distributions of water-soluble diacids and related compounds over the high biological productivity ocean, suggesting requirement for the reassessment of feedbacks of marine-derived SOA on climate forcing over the remote oceanic regions.

Particulate Organic Carbon export from upper Indian Ocean using 234Th/238U and 210Po/210Pb disequilibria

Date: 2015-01-27
Speaker: Dr. R. Rengarajan
Venue: Ground Floor Lecture Hall

Abstract

Climate change, rising atmospheric carbon dioxide, excess nutrient inputs, and pollution in its many forms are fundamentally altering the chemistry of the ocean, often on a global scale and, in some cases, at rates greatly exceeding those in the historical and recent geological record. Major observed trends include a shift in the acid-base chemistry of seawater, reduced subsurface oxygen both in near-shore coastal water and in the open ocean, rising coastal nitrogen levels, and widespread increase in persistent organic pollutants. Most of these perturbations are tied to ocean warming, acidification and coastal eutrophication and change the type and magnitude of organic carbon exported to the ocean’s interior. 234Th238U and 210Po210Pb pair has been widely utilized in the quantification of particulate scavenging and cycling of lithogenic and biogenic particulate matter in marine system. I will present preliminary results on carbon export to the deep oceans using 234Th/238U and 210Po/210Pb disequilibria in the water column obtained from recent ocean cruises under GEOTRACES and SIBER programmes.

High Energy Emission in Blazars

Date: 2015-01-27
Speaker: Mr. Pankaj Kushwaha
Venue: Room # 006 (Thaltej Campus)

Abstract

Blazars comprised of BL Lacs and flat spectrum radio quasar are radio-loud active galactic nuclei having a relativistic jet seen at very small angles to our line of sight. They are characterized by a rapid and highly variable non-thermal continuum emission across the electromagnetic spectrum dominated by jet emission with a distinctive double-hump spectral energy distribution profile. The low energy hump (IR-to-UV/X-rays) is the result of synchrotron emission from relativistic non-thermal electrons in the jet. However, the nature (leptons/hadrons) and origin (inverse Compton/proton-synchrotron/cascades) of high energy hump (X-rays-gamma-rays) is not very clear. The availability of almost simultaneous monitoring of a rich sample of blazars have made the blazar SED modelling one of the strongest tool to diagnose the physical processes in blazars. In this seminar, I will be presenting few of the interesting results obtained from my studies done during last couple of years to probe the high energy emission in blazars, particularly for OJ 287 and PKS 1222+216.

Permian-Triassic Extinction: Some recent results

Date: 2015-01-23
Speaker: Vinai Kumar Rai
Venue: Room #114 (Thaltej campus)

Abstract

Effects of Magnetospheric currents and High latitude ionospheric irregularities on the surface of Earth.

Date: 2015-01-22
Speaker: Dr. Swadesh Patra
Venue: Ground Floor Lecture Hall

Abstract

Space weather is generally quantified using a few numerical indices. The measurement and prediction of these indices are crucial in understanding space weather. We model the Dst and AL indices using a low order model and explore the possible contributions of the various magnetospheric currents. The most visible and well known impact of the space weather is seen in the field of global positioning. I will talk about the challenges faced at the higher latitudes and some of the instruments that our group at the University of Oslo has been working on. Recent results from the modeling and prediction of the scintillations in the Scandinavian sector will be discussed

Optical Imaging / Instrumentation in Applied Sciences: Synergies and Ideas for Astronomical Instrumentation

Date: 2015-01-22
Speaker: Dr. Mudit Srivastava
Venue: Room # 113 (Thaltej Campus)

Abstract

Optical Imaging Techniques and instruments have been used extensively in several application domains, ranging from fundamental research (e.g. Astronomy and Astrophysics) to applied and commercial research e.g. Life sciences, bio-medical, semi conductors etc. These two extreme domains of applications offer different kind of constraints on the several important aspect of instrument development e.g. financial, technical, complexity, scope, life cycle, compliances etc. While instrumentation in pure science research is driven by objectives set by scientific queries, can be very complex, specialized and can only avail to a specified set of people/experimental groups, instrumentation for the other domain has to be user's friendly, and more important cost effective. In this talk, I would emphasize on the similarities in the instrumentation between these two domains and fews ideas that could be imported for the development of astronomical instrumentation.

SUSY Dark Matter in Universal and Nonuniversal Gaugino Mass Models

Date: 2015-01-22
Speaker: Prof. D.P. Roy
Venue: Room No. 469

Abstract

Petrological, Geochemical and U-Pb Zircon Geochronological Studies of the Bundelkhand Granitoid Complex, Central India: Constraints on Archean Crustal Evolution

Date: 2015-01-20
Speaker: Dr. Batuk Kumar Joshi
Venue: Ground Floor Lecture Hall

Abstract

This study investigates the major and trace element compositions and zircon U-Pb ages (SIMS) of granitoids from Bundelkhand Craton, Central India and draws conclusions on their petrogenesis, emplacement ages and evolution. The secular and geochemical diversity of the granitoids in the complex ranges from sodium-rich TTGs (3.3-2.5 Ga) to calc alkaline, potassium-rich granitoids (2.57-2.52 Ga), which points towards a change in the source of granitoids from meta-basaltic material (TTGs) to variable sources with inputs from mantle-derived material and recycled crustal lithologies (calc alkaline granitoids). The U-Pb geochronology of the granitoids indicate that evolution of the craton was episodic and started as early as Paleoarchean. At 2.57-2.52 Ga, Bundelkhand experienced a rapid period of voluminous magmatic activity that produced a variety of plutonic rocks deriving from enriched mantle (e.g. sanukitoids) as well as crustal sources (intracustal granites). In conclusion, the Bundelkhand craton grew intensively due to a new type of tectono-magmatic event near the Archean-Proterozoic boundary and was stabilized by 2.5 Ga.

Comments on Flavour mix, energies and fluxes of high energy astrophysical neutrino events seen at ICECUBE

Date: 2015-01-20
Speaker: Prof. Sandip Pakvasa
Venue: Room No. 469

Abstract

Development of LIBS sensor for monitoring of CO2 leak in carbon sequestration

Date: 2015-01-19
Speaker: Prof. Jinesh Jain
Venue: Ground Floor Lecture Hall

Abstract

Leggett-Garg Inequalities and Device-Independent Randomness

Date: 2015-01-19
Speaker: Dr. Sujit K. Choudhary
Venue: Room No. 469

Abstract

Leggett-Garg inequalities (LGI) are constrains on certain combinations of temporal correlations obtained by measuring one and the same system at two different instants of time. The usual derivations of LGI assume macroscopic realism per se and non-invasive measurability. We derive these inequalities under a different set of assumptions, namely the assumptions of predictability and no signalling in time (NSIT). As a novel implication of this derivation, we find application of LGI in randomness generation. It turns out that randomness can be generated from temporal correlations, even without knowing the details of the experimental devices, provided the observed correlations violate LGI but satisfy NSIT.

In-situ search and characterization of presolar silicate grains

Date: 2015-01-16
Speaker: Mr. Manish N. Sanghani
Venue: Room #114 (Thaltej campus)

Abstract

Presolar grains are very small dust grains with anomalous isotopic compositions than that of the normal solar system materials. Various types of presolar grains like carbide, nitride, oxide and silicate have been identified and analysed in some of the primitive meteorite samples using sophisticated techniques. Out of these four types, presolar silicate grains are special and can be found only using in-situ ion imaging technique. Some of the silicate grains are believed to be condensed in the outer envelopes of the giant stars like supernova. Isotopic compositions of these grains are useful to constrain stellar nucleosynthesis processes. In the talk, various types of presolar grains will be briefly discussed. Importance of presolar silicate grains will be examined and two different methods to search these grains will be compared. After classifying silicate grains into different groups, some recent in-situ search results by ion-imaging at PRL NanoSIMS will be presented. Finally, proposed stellar sources for anomalous silicate grains will be evaluated along with insights for the future prospects.

In-situ search and characterization of presolar silicate grains

Date: 2015-01-16
Speaker: Mr. Manish N. Sanghani
Venue: Room #114 (Thaltej campus)

Abstract

Universality in the lepton sector

Date: 2015-01-16
Speaker: Prof. N. G. Deshpande
Venue: Room No. 469

Abstract

Radio Continuum Studies of Wolf-Rayet Galaxies

Date: 2015-01-15
Speaker: Dr. Shweta Srivastava,
Venue: Room # 113 (Thaltej Campus)

Abstract

The study of Wolf - Rayet (WR) galaxies plays an important role in understanding the properties of the star-forming events. The WR galaxies typically exhibit spectral features of WR stars which are indicative of young star-burst. This talk will cover the observed spectral energy distribution from 150 MHz to 10 GHz in a sample of WR galaxies using data obtained from the Giant Metrewave Radio Telescope (GMRT) and literature. The distance to the galaxies range from 4 - 60 Mpc and optical size from 0.8 - 9 arc-min. When the mechanism such as emission, absorption and energy loss, becomes active in these galaxies, the radio spectrum found to exhibit a variety of spectral shapes.

Global signatures of Little Ice Age and Medieval Warm Period in the climatic records from the southern Saurashtra Coast during the last two Millennia

Date: 2015-01-13
Speaker: Ms. Upasana Banerji
Venue: Ground Floor Lecture Hall

Abstract

The climate during the last two millennium witnessed both warming and cooling periods in the form of Medieval Warm Period (MWP) and Little Ice Age (LIA). These past global climate changes have strong regional expression. Studies from Indian subcontinent have highlighted the existence of MWP and LIA. However, there remains a knowledge gap regarding such global event from the western India. In view of this, mudflats from the southern Saurashtra coast, Gujarat were selected for the climatic reconstruction. The study aims to reconstruct the climatic variability observed during the last two millennia and to correlate the present finding with the global climatic events such as MWP and LIA. On the basis of geochemical proxies supported by C-14 dating, the preliminary results suggest that the Saurashtra region also responded to global climatic events such as MWP and LIA.

Testing New Physics Effects in B -> K^* l^+ l^-

Date: 2015-01-13
Speaker: Dr. Rahul Sinha
Venue: Room No. 469

Abstract

We show how the most general parametric form of the standard model amplitude for B -> K* l^+ l^- can take into account comprehensively all contributions within the standard model. This parametric form of the amplitude gives a new relation that does not rely on any approximations, however, innocuous. The violation of this relation provides a smoking gun signal of new physics. We use 1 fb^{-1} LHCb data to show that a robust signal of new physics is already being seen.

Recent developments in the marine N2 fixation studies: New results from the North Atlantic Ocean

Date: 2015-01-06
Speaker: Dr. Arvind Singh
Venue: Ground Floor Lecture Hall

Abstract

Global N2 fixation results might have been hampered by the use of inadequate methodology. Recent studies have highlighted various problems in the previous methods. In addition, some impurities have been detected in the tracer used to estimate N2 fixation. In this seminar, we shall discuss all such issues along with some new results from the North Atlantic Ocean.

Mars Orbiter Payload Discussions - Observing Mars in the NIR: Current status & potential for future

Date: 2015-01-02
Speaker: Indhu Varatharajan & Neeraj Srivastava
Venue: Room #114 (Thaltej campus)

Abstract

Mars Orbiter Payload Discussions - Mars Orbit Dust and Lightning Experiment for MOM-2 Orbiter

Date: 2015-01-02
Speaker: Dr. Jayesh Pabari
Venue: Room #114 (Thaltej campus)

Abstract

Mars Orbiter Payload Discussions - Observing Mars in the NIR: Current status & potential for future

Date: 2015-01-02
Speaker: Indhu Varatharajan & Neeraj Srivastava
Venue: Room #114 (Thaltej campus)

Abstract

Mars Orbiter Payload Discussions - Mars Orbit Dust and Lightning Experiment for MOM-2 Orbiter

Date: 2015-01-02
Speaker: Dr. Jayesh Pabari
Venue: Room #114 (Thaltej campus)

Abstract

2014

Isotopic tracing of atmospheric mineral dust over Oceans

Date: 2014-12-30
Speaker: Dr. Ashwini Kumar
Venue: Ground Floor Lecture Hall

Abstract

Atmospheric mineral dust has been recognized as an important constituent in the earth climate system because of their significant impact on various atmospheric and oceanic processes. In order to assess the impact of dust on climatic processes, it is very important to identify the sources of transported dust. Recently, radiogenic isotopes have been efficiently used for tracing atmospheric dust provenance and its transport over the oceans. In this talk, I will highlight on the transatlantic dust transport using radiogenic isotopes (Pb, Sr and Nd).

Dissolved inorganic carbon (DIC) and its delta-13C in the Ganga(Hooghly) river estuary: Evidence of DIC generation via organic carbon degradation and carbonate dissolution.

Date: 2014-12-26
Speaker: Dr. Tarun Kumar Dalai
Venue: Ground Floor Lecture Hall

Abstract

A geochemical perspective of the Mid-Holocene sedimentation in the Great Rann of Kachchh.

Date: 2014-12-23
Speaker: Mr. Anirban Chatterjee
Venue: Ground Floor Lecture Hall

Abstract

The low lying salty wasteland of the Great Rann of Kachchh is a unique Quaternary terrain of Western India. It has witnessed complex interplay of tectonics and sea-level change, within the short span of Holocene. In addition, many scholars believe it to be a delta complex of a paleo-river system fed by Himalayan glaciers during the mid-Holocene period. This hypothesis is interwoven with the evolutionary history of the Harappan Civilisation. Thus, decoding of the sedimentary history of the Great Rann of Kachchh is not only geologically significant, but also has profound geo-archaeological importance. In this talk I would present results of our geochemical study in the basin, carried out in an effort to decipher the sediment sources and understand the depositional pathways.

High Scale Mixing Unification for Dirac Neutrinos

Date: 2014-12-23
Speaker: Dr. Gauhar Abbas
Venue: Room No. 469

Abstract

Starting with high scale mixing unification hypothesis, we investigate the renormalization group evolution of mixing parameters and masses for Dirac type neutrinos. Following this hypothesis, the PMNS mixing angles and phase are taken to be identical to the CKM ones at a unifying high scale. Then, they are evolved to a low scale using renormalization-group equations. The renormalization group evolution "naturally" results in a non-zero and small value of leptonic mixing angle $\theta_{13}$. One of the important predictions of this work is that the mixing angle $\theta_{23}$ is non-maximal and lies only in the second octant. We also derive constraints on the allowed parameter range for the SUSY breaking and unification scales, for which this hypothesis works. The results are novel and can be tested by present and future experiments.

Dynamical tunneling versus quantum coherent control

Date: 2014-12-22
Speaker: Prof. Srihari Keshavamurthy
Venue: Room No. 469

Abstract

Quantum coherent control is an area of active research. However, recently, studies are starting to determine the extent of quantumness needed for exerting control using external fields. At the same time, we now have a fairly detailed understanding of the process of dynamical tunneling and its mechanisms from a phase space perspective. In this talk I will present some of our recent results that establish the importance of dynamical tunneling for the coherent control scenario. Interestingly, resonance and chaos assisted tunneling can thwart simple but elegant coherent control approaches.

Dual frequency SAR: A proposal for Mars 2 mission

Date: 2014-12-19
Speaker: Dr. Shiv Mohan
Venue: Room #114 (Thaltej campus)

Abstract

Dual frequency SAR: A proposal for Mars 2 mission

Date: 2014-12-19
Speaker: Dr. Shiv Mohan
Venue: Room #114 (Thaltej campus)

Abstract

Estimation of Solar EUV flux rate during Strong, Mid and Weak Solar flares using GPS satellite data

Date: 2014-12-19
Speaker: Mr. Talwinder Singh
Venue: USO seminar room

Abstract

Correlation of Solar Extreme Ultraviolet (EUV) photon flux rate in 26-34 mm spectral band during Solar flares will be shown with a GNSS Solar Flare Activity Indicator (GSFLAI) which is defined as the gradient of ionospheric Vertical Total Electron content rate vs. cosine of Solar Zenith Angle in day hemisphere. GSFLAI is measured from data collected by global network of dual frequency GPS receivers. Extreme ultraviolet photon flux data in 26-34 nm range was obtained from SEM instrument onboard SOHO spacecraft. GSFLAI for 60 X class flares, 320 M class flares and 300 C class flares occurred since 2001 was directly compared with EUV Solar flux rate data to show the correlations. It was found that GSFLAI and EUV flux rate have a linear relationship for all class of flare hence showing that the data from global network of GPS receivers to be a potential proxy for direct measurements of Solar EUV photon flux.

High Mass X-ray Binary Pulsars

Date: 2014-12-18
Speaker: Dr. Sachindra Naik
Venue: Room # 113 (Thaltej Campus)

Abstract

High Mass X-ray Binary (HMXB) pulsars are binary pulsars which consist of a neutron star (compact object) and a massive optical companion star orbiting around the common center of mass. Depending on the spectral-type of optical companion star, these pulsars are classified as Be/X-ray binary pulsars and Supergiant X-ray binary pulsars. Though mass accretion takes place from the massive optical companion star to the compact object, the difference in the mode of mass accretion is the cause of difference in the observed X-ray properties. Pulsars in these binary systems are highly variable in X-ray bands. Be/X-ray binary pulsars show regular and periodic X-ray outbursts whereas the pulsars in supergiant X-ray binaries show irregular and random variability in X-ray intensity. Timing and broad-band X-ray spectral properties of a few Be/X-ray binary pulsars and supergiant X-ray binary pulsars will be discussed. Along with X-ray properties, optical and infrared properties of the Be companion star (in Be/X-ray binary pulsars) will also be discussed.

Solar Physics and Sun-Earth Connection

Date: 2014-12-18
Speaker: Prof. P. K. Manoharan
Venue: Ground Floor Lecture Hall

Abstract

This talk will cover the basics of solar activity and discuss some examples of Sun-Earth connection solar events. In the space weather studies, the expected chain of actions from Sun to inner heliosphere are discussed. Moreover, in a solar event, its magnetic configuration plays a crucial role in making the effective reconnection with the earth's magnetosphere. A brief discussion on co-rotating interaction region (CIR) will also be given

Time-resolved aerosol inorganic chemical composition and precursor gases over Ahmedabad: Gas-aerosol Equilibrium Characteristics.

Date: 2014-12-16
Speaker: Mr. A.K. Sudheer
Venue: Ground Floor Lecture Hall

Abstract

Chemical composition of ambient aerosol exhibits large variability on a diurnal cycle and it requires high time-resolved measurements in order to study factors influencing the composition. We measured aerosol water-soluble ionic constituents and related trace gases, viz HCl, HNO3 and NH3 with a time resolution of one hour at Ahmedabad using Ambient Ion Monitor System. The aerosol composition and trace gas concentrations were used to verify gas-aerosol equilibrium over this urban environment using an equilibrium model. The results and implications will be discussed in this talk.

Sodium in the Upper Atmosphere

Date: 2014-12-15
Speaker: Dr. Sumanta Sarkhel
Venue: Ground Floor Lecture Hall

Abstract

The investigations on the altitude distribution of neutral Sodium (Na) atoms and Na airglow have been carried out for decades in order to unveil many mysteries in the Earth's upper atmosphere. Even after significant research work done on the upper atmospheric neutral Na atoms and Na airglow, several facts still remain unanswered and unattended. One such question can be posed whose answer is unknown: What are the species that actually contribute to the Na airglow emission? In addition to this unanswered question, a few puzzling phenomena were recently discovered in the neutral Na layer that need to be explained in the new direction. This seminar will be dedicated in order to find the answer of such unresolved facts related to the Na airglow emission mechanism. The discussion will also be carried out on the physical process behind unusual events observed in the neutral Na layer from different observational sites using various active and passive remote sensing techniques. All interested are welcome.

S-process Nucleosyntheis in AGB Stars: Insights from Presolar Grains

Date: 2014-12-12
Speaker: Mr. Lalit Kumar Shukla
Venue: Room #114 (Thaltej campus)

Abstract

Asymptotic Giant Branch (AGB) stars as interstellar medium (ISM) polluter were significant contributors to the molecular cloud from which our solar system formed. Presolar Grains found from primitive meteorites (in parts per million/billion level) confirm and provide an unique opportunity to understand stellar nucleosynthsis in these stars with amazing precision, never achieved by any other means. Astronomical observations and theoretical modeling indicate AGB stars as major astronomical site for production of slow-processed (s-processed) heavy elements. In this talk, I will briefly describe AGB phase of stellar evolution and s-process nucleosynthesis. My major concern of the discussion will be challenges and importance of measuring isotopic compositions of heavy elements present in trace amounts in presolar grains.

S-process Nucleosyntheis in AGB Stars: Insights from Presolar Grains

Date: 2014-12-12
Speaker: Mr. Lalit Kumar Shukla
Venue: Room #114 (Thaltej campus)

Abstract

Elasto plastic response of reversibly crosslinked biopolymer bundles

Date: 2014-12-11
Speaker: Dr. Poulomi Sadhukhan
Venue: Room No. 469

Abstract

We study the response of crosslinked F-actin bundles to driving forces through a simple analytical model. Two failure modes under load can be defined. Brittle failure is observed when crosslinks suddenly and collectively unbind, leading to catastrophic loss of bundle integrity. During ductile failure, on the other hand, bundle integrity is maintained, however at the cost of crosslink reorganization and defect formation. We present phase diagrams for the onset of failure, highlighting the importance of the crosslink stiffness. We evidence how the introduction of defects can lead to complex elasto-plastic relaxation processes, once the force is switched off. Depending on, both, the time-scale for defect motion as well as the crosslink stiffness, bundles can remain in a quasi-permanent plastically deformed state for a very long time.

An overview of laboratory studies of atmospheric chemistry and applications

Date: 2014-12-11
Speaker: Dr. Chaithanya D. Jain
Venue: Ground Floor Lecture Hall

Abstract

Air pollution problems like, visibility degradation, green house effect, acid rain, ozone depletion are continuously increasing in the recent years and hence have increased the interest in the atmospheric chemistry research. Laboratory studies on degradation mechanism, kinetic and spectroscopic measurements are useful to address these problems through a selective and controlled approach for the reactions involving a particular trace gas species. Specific methods and approaches are used to get the precise data depending upon the species under investigation. Results obtained from the laboratory studies will be used as input parameters in the computational models. Model predictions of the reactivity in the atmospheric conditions are then compared with the results obtained from the field measurements. This helps us in better understanding of the atmospheric processes which control the air quality and climate change. In the present talk some of the important laboratory study methods used will be presented along with a brief introduction to atmospheric chemistry. The second part of the talk will focus on the direct formation of HO2 radicals from the photo excitation of aromatic compounds as an example of laboratory studies.

Black Carbon Aerosol Emissions of India and Their Transport Pathways

Date: 2014-12-10
Speaker: Dr. Harish Gadhavi
Venue: Ground Floor Lecture Hall

Abstract

Black carbon particles in the atmosphere are absorbing type of aerosols. They are health hazard and play unique and important role in determining regional and global climate. However, chemical transport models have been consistently under predicting their concentration over India and surrounding oceans. Emission inventories are major source of uncertainties in models. Comparative performance of emission inventories, transport pathways for black carbon load over Southern India and role of atmospheric processes such as wet-deposition will be discussed during the talk.

Biogeochemical study of freshwater ecosystems in India.

Date: 2014-12-09
Speaker: Ms. Rupa Mukerjee
Venue: Ground Flooe Lecture Hall

Abstract

Freshwater ecosystems are necessary to sustain life. Humans rely on freshwater systems not only for drinking water, but also for agriculture, transportation, energy production, industrial processes, and the extraction of fish and other products. Excess reactive nitrogen from anthropogenic sources such as fertilizers, industrial sewage, and other terrestrial inputs has led to large changes in aquatic biogeochemical cycles which, in turn, led to eutrophication and hence, water quality degradation, oxygen deficiency, fish killing and shift in species composition. Therefore, mechanisms by which freshwater systems can reduce local and downstream nutrient concentrations are becoming increasingly important and for that we need to first identify the source of these excess nutrients. In this talk, I will briefly discuss biogeochemistry of some of the lakes and wetlands in India and proposed plan for my PhD work

S-32 in presolar grains: evidence for neutron capture at high neutron density

Date: 2014-12-05
Speaker: Dr. Kuljeet Kaur Marhas
Venue: Room #114 (Thaltej campus)

Abstract

S-32 in presolar grains: evidence for neutron capture at high neutron density

Date: 2014-12-05
Speaker: Dr. Kuljeet Kaur Marhas
Venue: Room #114 (Thaltej campus)

Abstract

Study of QPO in the black hole source GRS 1915+105 with NuSTAR data

Date: 2014-12-04
Speaker: Ms. Anjali Rao
Venue: Room # 113 (Thaltej Campus)

Abstract

Timing studies of the black hole binaries reveal the presence of the quasi periodic oscillations in the light curves. However, it is rather difficult to establish the oscillatory nature of the spectral component from the spectral studies. In this talk, we will discuss how the data from NuSTAR has helped to understand the link between quasi periodic oscillations and the spectral components. We studied a black hole source GRS 1915+105 with the NuSTAR data and the results will be discussed in the talk.

Holocene environments of the Great Rann of Kachchh, Western India.

Date: 2014-12-02
Speaker: Dr. Niteshkumar N. Khonde
Venue: Ground Floor Lecture Hall

Abstract

The Great Rann of Kachchh (GRK) basin is a dried up floor of the former Arabian Sea gulf in the northern extremity of the Kachchh paleorift. GRK has remained one of the enigmatic terrains for geologists due to its unique inundation pattern and geomorphic settings. The seasonal inundation/drying cycles always generated interest for common man and earth scientists. The GRK has also played an important role in Harappan flourishment and provided transport pathways for the maritime activities. Geologically, GRK has served as a Holocene depocenter which accumulated huge pile of sediments preserving past records of environmental changes and climatic history. It is believed that the GRK has gone through the complex interplay of the climate-tectonic forces throughout its geological past. Despite several scientific issues the geological evolution of the GRK basin still remains to be understood. Some of the preliminary outcomes from the inundation pattern in Rann, surface sediments, exposed cliff sections along the island margins and subsurface sediments of Rann basin would be discussed.

Adaptive Optics and its applications in vision research

Date: 2014-12-02
Speaker: Krishnakumar Venkateswaran
Venue: USO seminar room

Abstract

A possible solution towards overcoming earth?s atmospheric turbulence aimed at providing high resolution astronomical images using ground based telescopes came through the advent of adaptive optics (AO). An AO system consists of a wavefront sensor to measure the optical distortions in the wavefront and an optical element to compensate the optical distortions. In 1953, Babcock proposed a method for compensating earth?s atmospheric turbulence but it was not until 1977 when Hardy and colleagues successfully demonstrated the use of AO in astronomy. Initially used for military purpose, AO made inroads in astronomy and is now being used almost as a staple part of any high resolution optical imaging system in astronomical telescopes. Liang et. al. (1992, 1994) was the first to demonstrate the use of a Shack Hartmann wavefront sensor to measure the monochromatic aberrations in the eye. Later, the AO group at the University of Rochester incorporated the wavefront sensor into adaptive optics ophthalmoscope (Liang et al., 1997). Roorda et al., (2002) combined conventional scanning laser ophthalmoscope and AO (Adaptive Optics Scanning Laser Ophthalmoscope ? AOSLO) correcting for both lower and higher order aberrations to obtain images with unprecedented lateral resolution resolving cones close to the fovea. In 2002 Drexler et al., and in 2003 Miller et al., combined AO with optical coherence tomography (OCT) to provide higher axial resolution. Many modified systems have since been developed combining different technologies such as OCT and SLO together along with AO to obtain high resolution images. Another application for AO systems is its use in correcting optical aberrations in human eye and hence delivers high resolution images on the retina. AO systems provide a way to compensate for the optical aberrations in real time helping us to understand the impact of different optical aberrations on human vision. Understanding optical aberrations structure in human eye leads to innovation in areas such as retinal imaging, intra-ocular lens design. In this presentation, we will discuss AO systems and its applications in vision research.

Adaptive optics and its applications in vision research

Date: 2014-12-02
Speaker: Dr. Krishnakumar Venkateswaran
Venue: USO Seminar Hall

Abstract

A possible solution towards overcoming earth’s atmospheric turbulence aimed at providing high resolution astronomical images using ground based telescopes came through the advent of adaptive optics (AO). An AO system consists of a wave front sensor to measure the optical distortions in the wave front and an optical element to compensate the optical distortions. In 1953, Babcock proposed a method for compensating earth’s atmospheric turbulence but it was not until 1977 when Hardy and colleagues successfully demonstrated the use of AO in astronomy. Initially used for military purpose, AO made inroads in astronomy and is now being used almost as a staple part of any high resolution optical imaging system in astronomical telescopes.

Presolar Grains in Antarctic Meteorites

Date: 2014-11-28
Speaker: Manish Sanghani
Venue: Room #114 (Thaltej campus)

Abstract

I will briefly introduce Antarctic meteorites and their search. Then I would talk about presolar grains and their classification. I will then take a few examples of Antarctic meteorites and their isotopic anomalies in context with presolar grains. Finally, the instrumental conditions for the in-situ search of presolar grains would be presented.

Presolar Grains in Antarctic Meteorites

Date: 2014-11-28
Speaker: Manish Sanghani
Venue: Room #114 (Thaltej campus)

Abstract

Payloads developed by SAC for Mars Orbiter Mission (MOM)

Date: 2014-11-27
Speaker: Moumita Dutta
Venue: Room No. 469

Abstract

--NA--

Airborne and Ground-based Infrared Remote Sensing at IMK-ASF

Date: 2014-11-26
Speaker: Dr. Mahesh Kumar Sha
Venue: Ground Floor Lecture Hall

Abstract

The Institute for Meteorology and Climate Research - Atmospheric Trace Gases and Remote Sensing (IMK-ASF) of the Karlsruhe Institute of Technology is one of the leading institutes in the world doing studies related to the processes in the atmosphere using infrared remote sensing techniques. This talk will give an overview of the various research activities undergoing at IMK-ASF and will focus on two of the projects namely, GLORIA (Gimballed Limb Observer for Radiance Imaging of the Atmosphere) and COCCON (Collaborative Carbon Column Observing Network). GLORIA is an imaging Fourier transform spectrometer operated on-board high altitude aircrafts. The GLORIA spectrometer is equipped with a large focal plane array measuring the emission of the earth's atmosphere in the mid-infrared spectral region. The instrument is gimbal mounted to allow measurements of the atmosphere in limb- and nadir-sounding geometry. The measurements performed with GLORIA provide high resolution information about the dynamics and chemistry of the upper troposphere and lower stratosphere region; some of the recent results will be presented. The second part of the talk focuses on ground based instrumentation used for measuring and monitoring greenhouse gases (GHG) thereby entangling the issue of global warming which is one of the major concerns for the survival on earth. The increase of GHGs since the pre-industrial era has led to an enhancement in the absorption and emission of infrared radiation by GHGs, leading to an overall warming of the earth's surface. Understanding the sources and sinks of these GHGs is therefore of huge importance. The existing measurement networks, dealing with carbon science using solar absorption spectroscopy will be addressed, whereas the focus will lay in the introduction of the COCCON project giving detailed information about the aim and methodology used. In addition; the potential of establishing such a network will be explained and some of the recent results will be presented.

Atmospheric Mineral Dust: Long-range transport and chemical processing.

Date: 2014-11-25
Speaker: Prof. M. M. Sarin
Venue: Ground Floor Lecture Hall

Abstract

This talk will highlight some of our recent results on atmospheric transport of mineral dust from the Indo-Gangetic Plain to the Bay of Bengal. The atmospheric supply of mineral dust, a dominant source of iron (Fe) to the ocean surface, has been asubject of major debate over the past two decades. The chemical form of soluble Fe and its bioavailability are the major issues in this debate and in assessing the impact on marine biogeochemistry. In vast areas of open ocean waters (Subarctic Pacific, Equatorial Pacific, and Southern Ocean: High Nutrient Low Chlorophyll (HNLC) regions), productivity is limited by the availability of this micronutrient (Fe). The studies carried out in HNLC regions have highlighted dust-mediated glacial-interglacial CO2 changes and emphasizethe need to further understand the atmospheric transport and deposition of mineral dust to the open ocean. In this context, several modelling studies have relied on the transport of mineral dust from arid and semi-arid regions as a dominant source of soluble iron to the open ocean. One of the important parameters in the atmospheric supply of Fe to sea water is the solubility of mineral dust. The significance of chemical processing of mineral dust by anthropogenic acidic species (H2SO4, HNO3) in enhancing the fractional solubility of aerosol iron has been suggested as a vital factor.

Interplay between Mutual Information and Success Probability: A Deeper Look into the Security of BB84

Date: 2014-11-21
Speaker: Goutam Paul
Venue: Room No. 469

Abstract

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Observations from SHARAD Subsurface Radar at the Mid Northern Latitudes of Mars

Date: 2014-11-21
Speaker: Mr. Santosh Choudhary
Venue: Room #114 (Thaltej campus)

Abstract

Observations from SHARAD Subsurface Radar at the Mid Northern Latitudes of Mars

Date: 2014-11-21
Speaker: Mr. Santosh Choudhary
Venue: Room #114 (Thaltej campus)

Abstract

Hilbert Space Theory of Classical Electrodynamics

Date: 2014-11-19
Speaker: Prof. Partha Ghose
Venue: Room No. 469

Abstract

--NA--

Nitrogen dynamics in forest soils.

Date: 2014-11-18
Speaker: Dr. Sanjeev Kumar
Venue: Ground Floor Lecture Hall

Abstract

Mass transport regimes in the solar protoplanetary disk − evidence from meteoritic components

Date: 2014-11-14
Speaker: Prof. Martin Bizzarro
Venue: Room #114 (Thaltej campus)

Abstract

Chondrite meteorites are fragments of asteroids that did not undergo melting and differentiation and, thus, provide a record of the earliest stages of the solar protoplanetary disk. Ordinary and enstatite chondrites are derived from parent asteroids that originated in the accretion region of terrestrial planets whereas the parent asteroids of the water-rich carbonaceous chondrites most likely accreted in the giant planet region. The dominant constituent of chondrites are millimeter-sized chondrules formed by transient heating events in the protoplanetary disk. Although it has long been accepted that chondrules formed 1 to 2 Myr after condensation of the solar system first solids, calcium-aluminium-rich inclusions (CAIs), recent high-resolution uranium-corrected Pb-Pb dates indicate that chondrule formation started contemporaneously with CAIs and lasted ~3 Myr. Moreover, chondrules from individual chondrites show variability in 54Cr/52Cr ratios, which track genetic relationships between early-formed solids and their respective reservoirs. Collectively, these observations indicate that chondrules from individual chondrite groups originated in different regions of the protoplanetary disk and were subsequently transported to the accretion regions of their respective parent bodies. In this talk, we report new uranium-corrected Pb-Pb ages as well as 54Cr/52Cr ratios for chondrules from enstatite, ordinary and various classes of carbonaceous chondrites. Our results indicate that chondrule populations from individual chondrite groups show a comparable age range of ~3 Myr. Chondrules from enstatite and ordinary chondrites show 54Cr/52Cr ratios restricted to inner solar system compositions. In contrast, carbonaceous chondrite chondrules record greater 54Cr/52Cr variability, with both inner and outer solar system signatures. These data require different outward mass transport regimes but limited inward transport of outer solar system material in the formation region of terrestrial planets during the main accretion phase of chondrite parent asteroids. We explore the role of protostellar jets and disk winds as potential mass transport mechanisms to account for the observed meteoritic data.

Mass transport regimes in the solar protoplanetary disk − evidence from meteoritic components

Date: 2014-11-14
Speaker: Prof. Martin Bizzarro
Venue: Room #114 (Thaltej campus)

Abstract

Energy conservation for a radiating charge in classical electrodynamics

Date: 2014-11-13
Speaker: Dr. Ashok K. Singal
Venue: Room # 113 (Thaltej Campus)

Abstract

It is shown that the well-known century-old disparity in classical electrodynamics between the power radiated in electromagnetic fields (from the familiar Larmor's formula, or in a relativistic case, from Li\'{e}nard's result) and the power-loss, as calculated from the radiation reaction (given by the Lorentz-Abraham-Dirac equation) on a charge undergoing a non-uniform motion, is successfully resolved when a proper distinction is made between the quantities expressed in terms of the retarded time and those expressed in terms of a ``real time''. It is shown that the expression for the real-time radiative power loss from a charged particle is somewhat different from the familiar formulas in the literature. A use of the standard formulation has resulted, among other things, in a potentially incorrect text-book formula (derived by Kardashev 1962 and in use ever since) for the life-times of electrons undergoing synchrotron losses in radio galaxies or supernova remnants. The correct formulation will be provided.

High resolution precipitation record from a stalagmite from Kotumsar cave, Chhattisgarh.

Date: 2014-11-11
Speaker: Ms. Shraddha Band
Venue: Ground Floor Lecture Hall

Abstract

Caves in India are used extensively to reconstruct past monsoon conditions. A stalagmite sample (KOT-1) collected from Kotumsar cave that grew between 5000 to 4000 yr BP, has been sub-sampled for stable isotope analysis using high resolution micromill technique. As the stalagmite banding is annual, the objective of the study was to find the traces of seasonal variability. Although in this particular sample the variability was not found other interesting results have come up. Contemporaneous to the stalagmite formation, archaeological evidences of burnt charcoal, millets were found. These interdisciplinary results can help in understanding man-climate relationship

Some Highlights of COSPAR 2014

Date: 2014-10-31
Speaker: Prof. S.V.S. Murty
Venue: Room #114 (Thaltej campus)

Abstract

Some Highlights of COSPAR 2014

Date: 2014-10-31
Speaker: Prof. S.V.S. Murty
Venue: Room #114 (Thaltej campus)

Abstract

Declining solar magnetic fields and Low Frequency Radio Astronomy: Is there a link?

Date: 2014-10-30
Speaker: Prof. P. Janardhan
Venue: Room # 113 (Thaltej Campus)

Abstract

Observations of solar polar magnetic fields during the past three solar cycles viz. cycles 21, 22 and 23 have shown that the solar magnetic fields have been steadily declining since about 1995. This steady decline has also caused a similar decline in solar wind microturbulence levels. In recent times low frequency, meterwave radio astromomy is gaining importance. However, the ionospheric cut-off frequency of about 25 MHz sets a limit on the lowest frequncies one can observe from the ground. Ionosonde records of the cut-off frequency in solar cycle 23 indicates that the cut-off is also reducing and there is indication that it may go below 10 MHz. This talk will try to briefly look at these aspects.

Crystallization of silicate melt droplets under non-contact conditions: Understanding chondrule formation in early solar system

Date: 2014-10-16
Speaker: Dr. Atul Srivastava
Venue: Room #114 (Thaltej campus)

Abstract

Crystallization of silicate melt droplets under non-contact conditions: Understanding chondrule formation in early solar system

Date: 2014-10-16
Speaker: Dr. Atul Srivastava
Venue: Room #114 (Thaltej campus)

Abstract

Vector perturbations in ELKO cosmology

Date: 2014-10-16
Speaker: Dr. Abhishek Basak
Venue: Room No. 469

Abstract

In this work we have analysed the first order vector perturbations in the context of inflationary model driven by non-standard spinor also known as ELKO. Unlike the standard scalar field driven inflation, the $\eta-i$ component of the first-order perturbed energy-momentum tensor of the ELKOS is non-zero indicating the plausibility of the generation of the pure vector part of the metric perturbation ($B_{i}$). The same component of the perturbed Einstein equation gives us the evolution equation of $B_{i}$. The evolution equation is solved under a condition on the background field which leads to super-inflation. Nearly time invariant and scale invariant solution for $B_{i}$ in super-horizon scale has been achieved.

Nutrient Variability in a Tropical Monsoonal Estuary.

Date: 2014-10-14
Speaker: Mr. Subha Anand S
Venue: Ground Floor Lecture Hall.

Abstract

Monsoonal estuaries are highly dynamic and unique ecosystems. Materials transported through rivers undergo various biogeochemical transformations here before reaching the sea.The processes occurring in estuaries are very rapid and vary with time and space. Intra- and inter seasonal variability of dissolved oxygen and nutrients were studied in a tropical monsoonal estuary (Zuari, Goa, India). A dual sampling approach was adopted by monitoring the changes (daily/alternate day) at a fixed location and at ten stations from upstream to mouth during spring and neap tides for about a year. This study evaluates the strength of biogeochemical and physical processes in regulating the variability in the estuary. Another goal of this study is to see the retention of anthropogenic inputs in the estuary. The results will be discussed in detail.

Some Conceptual Issues in Finite Density QCD

Date: 2014-10-14
Speaker: Professor Rajiv Gavai
Venue: Room No. 469

Abstract

While a mature subject by itself, finite density quantum chromo dynamics (QCD), and indeed any finite density field theory, turns out to have some hidden issues which affect the modern lattice computations of interesting physical quantities. We point out what they are, and propose ways to handle them.

Optical parametric oscillation (OPO) and its applications at above threshold and sub-threshold level

Date: 2014-10-13
Speaker: Mr. Vinayak Kumar
Venue: Ground Floor Lecture Hall

Abstract

The generation of plasma density irregularities in the post sunset/night time equatorial and low latitude ionosphere had been posing a challenge to the space science community. The comprehensive understanding of this phenomenon had been all the more important in the context of its role in the radio communication in general and the ground- satellite - ground communication in particular. Attempts will be made to build up the scenario and highlight some of the recent developments in this field/topic with specific emphasis to a particular and different approach in challenging the evasive problem.

Solar Thermal & Energetic Particle Spectrometer (STEPS) (Subsystem of ASPEX payload), onboard Aditya ? L1 mission

Date: 2014-10-10
Speaker: Mr. S. K. Goyal
Venue: Room #114 (Thaltej campus)

Abstract

Solar Thermal & Energetic Particle Spectrometer (STEPS) (Subsystem of ASPEX payload), onboard Aditya ? L1 mission

Date: 2014-10-10
Speaker: Mr. S. K. Goyal
Venue: Room #114 (Thaltej campus)

Abstract

Climate Change - IPCC versus Indian Research- a perspective

Date: 2014-10-07
Speaker: Prof. R Ramesh
Venue: Ground Floor Lecture Hall

Abstract

Reconstructing the paleoredox conditions using Delta-98 / 95 Mo in Black Shales

Date: 2014-09-30
Speaker: Ms. Sneha Sawant
Venue: Ground Floor Lecture Hall

Abstract

Ocean anoxia is preserved in Black Shale due to their formation under euxinic settings. Molybdenum (Mo) stable isotope system is a valuable tool for investigating ocean paleoredox conditions. Mo isotopic composition of seawater is determined by its relative removal in oxic and anoxic sinks. Mo isotopes fractionates during its removal from seawater under oxic conditions whereas it remains invariable during its precipitation in reducing sediments. Hence, Mo isotope composition of reducing sediments can be used to track the temporal variation in redox condition of the global ocean. The Mesoproterozoic-Early Cambrian period in the early history of the earth witnessed important evolutionary changes such as rise in atmospheric oxygen and changes in the biosphere. An attempt is being made to reconstruct the redox conditions during this period using Mo isotopes in black shales. Mo isotope composition of black shales was determined by double spike technique to correct isotope fractionation during sample purification and instrumental mass bias on MC-ICP-MS. In this talk, mechanisms of molybdenum fractionation under oxic-anoxic settings and some results on black shales from different Eras will be discussed.

Highlights of 14th International Conference on Luminescence and Electron Spin Resonance at Montreal, Canada

Date: 2014-09-26
Speaker: Dr. D. Banerjee
Venue: Room #114 (Thaltej campus)

Abstract

Highlights of 14th International Conference on Luminescence and Electron Spin Resonance at Montreal, Canada

Date: 2014-09-26
Speaker: Dr. D. Banerjee
Venue: Room #114 (Thaltej campus)

Abstract

Formation of current sheets through viscous relaxation

Date: 2014-09-12
Speaker: Sanjay Kumar
Venue: USO Seminar Hall

Abstract

From Parker’s magnetostatic theorem, formation of tangential discontinuities in magnetic field, or current sheets (CSs), are unavoidable in an equilibrium magnetofluid with infinite electrical conductivity and complex magnetic topology. These CSs are due to a failure of a magnetic field achieving forcebalance everywhere and preserving its topology while remaining in a spatially continuous state. The magnetic flux surfaces (MFSs) being the possible sites on which CSs develop, describing the magnetofluid evolution in terms of MFSs instead of vector magnetic field provides a direct visualization of the CS formation, helpful in understanding the governing dynamics. In this talk, I will discuss the magneto hydrodynamics simulations in which CS formation is demonstrated by employing an approach that utilizes MFSs. The simulations confirm development of CSs through a favourable contortion of MFSs, as the magneto fluid undergoes a topology-preserving viscous relaxation from an initial non-equilibrium state with twisted magnetic field. A crucial finding of this work is in its demonstration of CS formation at spatial locations away from the magnetic nulls.

Role of Saline-alkaline soils in estimation of silicate erosion rate in the Ganga plain

Date: 2014-09-09
Speaker: Ms. Jayati Chatterjee.
Venue: Ground Floor Lecture Hall

Abstract

Silicate erosion is one of the major sinks of atmospheric CO2 in million year time scale. Contemporary silicate erosion of all major global rivers including Ganga has been studied extensively. Major ion composition and Sr isotopic ratio of the rivers have been used as tools for this purpose. But, presence of saline-alkaline soils in the Ganga basin complicates the use of these tools, as they act as a source of dissolved ions to the river water. These soils have been chemically and isotopically characterized in the present study. Dissolved budget of the Ganga river system has been apportioned to various sources, e.g.,silicates, carbonates, saline-alkaline soils etc, by inversion of chemical and Sr isotopic data. The results will be presented in this talk. I will also discuss couple of papers from Goldschmidt 2014.

Challenging the evasive!

Date: 2014-09-08
Speaker: Prof. R. Sridharan
Venue: Ground Floor Lecture Hall

Abstract

Higher spin particles: Past, Present and Future

Date: 2014-09-04
Speaker: Prof. M. Sivakumar
Venue: Room No. 469

Abstract

In this talk I survey the evolution of the study of higher spin particles since the days of quantum mechanics, and end with recent developments including Vasiliev's higher spin theory and point out some open problems in this subject. In the process a recent work of mine on higher spin couplings will be discussed.

Mo isotopes in rivers, estuaries and the Indian Ocean: Implications to its fractionation and internal cycling.

Date: 2014-09-02
Speaker: Dr. Sunil Kumar Singh
Venue: Ground Floor Lecture Hall

Abstract

Molybdenum (Mo) isotopes are being used as a proxy to trace paleo-redox condition of oceans. Quantitative interpretation of Mo isotope records in marine sediment deposits to derive redox conditions of ancient oceans requires representative data on Mo input and its isotope composition to the oceans. This information is important to refine the contemporary isotope budgets of Mo and for using this isotope system to determine variability in the spatial extent of redox conditions of the ancient oceans. Mo concentration and its isotope composition have been measured in dissolved and particulate phases of the Indian rivers, estuaries and in the northern Indian Ocean to (i) assess the impact of physical/chemical weathering on the isotope fractionation of Mo, (ii) constrain its flux and delta-98Mo to the northern Indian Ocean (iii) its internal cycling in the northern Indian Ocean. Mo isotopes fractionate significantly during weathering and transport in rivers and estuaries. Sinking particles and bottom sediments could supply significant amount of lighter Mo isotopes to the water columns in the northern Indian Ocean. Detail results will be discussed in the seminar.

Informal discussion on current Sheet formation

Date: 2014-09-01
Speaker: Dr.Ramitendranath Bhattacharyya
Venue: USO Seminar Hall

Abstract

Chemical evolution of Milky way Galaxy

Date: 2014-08-29
Speaker: Mr. Sameer
Venue: Room #114 (Thaltej campus)

Abstract

Chemical evolution of Milky way Galaxy

Date: 2014-08-29
Speaker: Mr. Sameer
Venue: Room #114 (Thaltej campus)

Abstract

Understanding carbon and nitrogen cycling in the Cochin estuary and coastal Arabian Sea.

Date: 2014-08-26
Speaker: Ms. Bhavya. P. S
Venue: Ground Floor Lecture Hall

Abstract

Estuaries and coastal waters are a few of many victims of eutrophication caused by excessive nutrient loading due to anthropogenic interferences. Estuarine C and N assimilations are mainly controlled by C: N: P ratios rather than individual nutrient concentrations. Along with the nutrient ratio, the increasing pCO2 is also a major factor in regulating the photosynthesis in the estuarine waters. delta-13CDIC is used for identifying the sources of dissolved inorganic carbon (the substrate for photosynthesis) and also to understand the presence of anthropogenic CO2 in the ocean surface waters. In this talk, these interesting topics will be addressed on basis of our study conducted in the Cochin estuary, one of the eutrophic estuaries in India, and adjacent coastal Arabian Sea with special emphasis on the anthropogenic involvements

Carbon Dioxide: Observations and Modelling

Date: 2014-08-25
Speaker: Mr. Naveen Chandra
Venue: Ground Floor Lecture Hall

Abstract

The main motivation for studying Earth?s global carbon cycle is to enable scientists to predict future levels of CO2 in the atmosphere. This requires high understanding about regional distribution of CO2 fluxes. Regional flux estimation needs the combined study of observation and modelling, which is very much challenging. Modelling aspect of CO2 research and our measurements over Ahmedabad will be discussed in the seminar.

Formation of magnetic discontinuities in a magnetofluid with large electrical conductivity

Date: 2014-08-22
Speaker: Dinesh Kumar
Venue: USO Seminar Hall

Abstract

The high Lundquist number S (\approx 10^{12}) of the solar corona renders coronal magnetofluid to be near-ideal in a sense that the condition of flux-freezing holds to a good approximation. Under this condition of flux-freezing the coronal magnetofluid can be partitioned into contiguous subvolumes of fluid each of which entraps its own magnetic flux. If two such subvolumes press into each other and come into direct contact by squeezing out a third interstitial subvolume, then under favorable conditions the magnetic field is expected to get discontinuous at the common surface of interaction and a current sheet is formed there. In a near-ideal system the current sheets decay through magnetic reconnection as a minimum threshold in local S is achieved where the otherwise negligible Ohmic dissipation becomes important. The above process of CS formation and its subsequent decay is responsible for a multitude of eruptive phenomena observed in the solar corona and provides a possible explanation for the corona to be at million degree Kelvin temperature. In this talk, I will present numerical demonstration of the formation of magnetic discontinuities based on suitable Initial Value Problems (IVPs) relevant to coronal physics.

Looking for Minimal Linear Seesaw Model at the Large Hadron Collider

Date: 2014-08-22
Speaker: Gulab Bhambaniy
Venue: Room No. 469

Abstract

In this talk I will discuss the Minimal Linear Seesaw Model(MLSM) in which two fermion singlets with opposite lepton numbers are added to the Standard Model (SM). The smallness of neutrino mass is explained through the small lepton number violating (LNV) Yukawa coupling. This allows to have both, TeV scale new physics as well as sizable light-heavy mixing, which are needed to have significant phenomenology of the model at LHC. The model is fully reconstructable in terms of neutrino oscillation parameters apart from the overall coupling. This coupling can be constrained from vacuum meta-stability and lepton flavor violating (LFV) process. The phenomenology of heavy neutrinos in this model at 14 TeV LHC will be discussed. The heavy neutrinos can be produced at LHC via S-channel and vector boson fusion (VBF) type of diagrams. The decay of heavy neutrinos lead to trilepton with missing transverse energy signal and VBF type signal which is characterized by two extra forward tagged jets. The significance of the signals will be discussed.

The power law Starobinsky model

Date: 2014-08-21
Speaker: Girish Chakravarty
Venue: Room No. 469

Abstract

In this talk I shall briefly discuss about the Starobinsky Model of Inflation and how we arrived at power-law form of the Starobinsky model from generalized curvature coupled models to tackle some of the issues in Starobinsky model. I shall also show that the most general Higgs-inflation models are equivalent to power-law correction to Einstein gravity and shall briefly try to discuss how these models are motivated by supergravity with the appropriate choice of the Kahler potential and superpotential.

Dissolved major ions, Sr and 87Sr/86Sr and sigma-Nd of the Godavari river system: Implications to chemical weathering rates and 87Sr and 143Nd fluxes to the ocean

Date: 2014-08-19
Speaker: Mr. K. Damodararao
Venue: Ground Floor Lecture Hall

Abstract

Rivers are the principal pathways by which dissolved and particulate matters from continental weathering are transported to the oceans. The river water chemistry and elemental flux transported by them to the oceans are needed to understand the major process at the surface of the Earth. The present study deals with the Godavari River Basin, the largest river system of the peninsular India, by studying the chemical and Sr, Nd isotope compositions in the both dissolved and particulate phases. This study provides not only the estimates of the weathering fluxes from this basin to the Bay of Bengal but also evaluate the role of two distinct lithology, the Deccan basalts and Archean geniesses in controlling these fluxes. These results will be discussed in detail in the seminar.

Multi-wavelength Investigations of Solar Eruptive Phenomena

Date: 2014-08-19
Speaker: Upendra Kushwaha
Venue: USO Seminar Hall

Abstract

Solar flares are characterized by the sudden release of excess energy stored in the magnetic fields of solar corona. The modern multi-wavelength observations have immensely improved our understanding of the various physical processes occurring in different atmospheric layers of the Sun during a solar flare. The standard flare model has been successful in broadly recognizing these physical processes as the consequence of large-scale magnetic reconnection in the corona. In this talk, I will present multi-wavelength studies of a few intriguing solar flares and associated eruptive phenomena. For these investigations, we have analyzed contemporary data sets at superior temporal, spatial and spectral domains from various space -based observatories including RHESSI, SDO, TRACE, and NoRH. I will highlight important results of these studies which aim to provide crucial evidences to understand pre-flare conditions, triggering mechanism, and energy release processes.

Non-interferometric measurement of Pancharatnam phase

Date: 2014-08-13
Speaker: A. Aadhi
Venue: Room No. 469

Abstract

Pancharatnam phase is so called geometrical phase in optics associated with the polarized light. When a polarized light evolves on the Poincare sphere, its initial and final state acquire a phase difference, even though it comes back to its initial state, which is purely a geometrical consequence of the evolution of the state on the Poincare sphere. Pancharatnam found that for the cyclic evolution the phase difference will be half of the solid angle subtended by the closed path during the evolution. In general interference between the initial and final state is used to measure the Pancharatnam phase. In this talk I will discus about non-interferometric way of measuring the Pancharatnam phase. Further it can be extended to measure non-cyclic evolution of the initial state.

Space weather phenomena during the modern era

Date: 2014-08-11
Speaker: Prof. Bruce T. Tsurutani
Venue: USO Seminar Hall

Abstract

I will discuss some new aspects of space weather developed over the last few years. The causes of low geomagnetic activity during the recent solar minimum (2009, not 2008) will be explained. Geomagnetic activity during the CAWSES II interval of 5-17 March 2012 (rising phase of the solar cycle) will be discussed in some detail. HILDCAAs and interplanetary Alfven wave effects (during solar cycle declining phases) will be reviewed. This will be presented to serve as background to new results on the effects of HILDCAAs/High Speed Streams on relativistic electron acceleration, ionospheric TEC enhancements and NOx enhanced radiation. Finally I will discuss the effects of a “perfect” ICME might have on the Earth and its environment

Quantum Scattering

Date: 2014-08-11
Speaker: Ananya Ghatak
Venue: Room No. 469

Abstract

Fluctuations in Relativistic Causal Hydrodynamics

Date: 2014-08-11
Speaker: Avdhesh Kumar
Venue: Room No. 469

Abstract

Hydrodynamic fluctuations arise due to finite particle number fluctuations in a given fluid cell. Intensity of these fluctuations is determined by equal time correlation functions which represents the correlation between the value of a given quantity to one space-time point to another. The dynamical properties of these fluctuations can be studied by time dependent correlation functions. In this seminar I shall discuss how the general theory of quasi stationary fluctuation can be used to calculate the hydrodynamic fluctuations in several relativistic causal hydrodynamics and Navier-Stokes hydrodynamics (acausal). We shall also discuss the time dependent nature of the hydrodynamic fluctuations for case of different relativistic hydrodynamics using one dimensional boost invariant (Bjorken) flow.

Space Weather Phenomena during the Modern Era

Date: 2014-08-11
Speaker: Bruce T. Tsurutani,
Venue: USO Seminar Hall

Abstract

I will discuss some new aspects of space weather developed over the last few years. The causes of low geomagnetic activity during the recent solar minimum (2009, not 2008) will be explained. Geomagnetic activity during the CAWSES II interval of 5-17 March 2012 (rising phase of the solar cycle) will be discussed in some detail. HILDCAAs and interplanetary Alfven wave effects (during solar cycle declining phases) will be reviewed. This will be presented to serve as background to new results on the effects of HILDCAAs/High Speed Streams on relativistic electron acceleration, ionospheric TEC enhancements and NOx enhanced radiation. Finally I will discuss the effects of a ?perfect? ICME might have on the Earth and its environment.

Generalized Higgs Inflation Model

Date: 2014-08-08
Speaker: Girish Kumar Chakravarty
Venue: Room No. 469

Abstract

In this talk I shall briefly discuss about scalar-curvature coupled Higgs-inflation model \xi\phi^2 R and the problems in this model in establishing Higgs as the Inflaton which drives the inflation and how could we overcome these by generalizing such a model to \xi\phi^a R^b. We shall also discuss about the equivalence of the Jordan and Einstein frames using our obtained results.

Infrared Carbon Stars

Date: 2014-08-07
Speaker: Prof. N. M. Ashok, PRL
Venue: Room # 113 (Thaltej Campus)

Abstract

Infrared Carbon Stars(IRCSs) are carbon stars identified only by their infrared properties. The term Infrared Carbon Stars appeared in the literature as a consequence of one of the significant discoveries from the IRAS (Infrared Astronomy Satellite) mission. IRCSs are usually invisible or very faint in the optical. Their energy distribution is characterized by the emission from the dust grains contained in the circumstellar envelope that absorb the radiation from the central star which makes the detection at optical wavelengths difficult. The IRCSs are important objects to understand the evolutionary sequence in the asymptotic giant branch(AGB) and post-AGB phases of carbon rich stars. The photometric and spectroscopic properties in the infrared will be discussed.

delta-D and delta-18-O of rainfall over India: model vs. observation.

Date: 2014-08-05
Speaker: Mr. Midhun M
Venue: Ground Floor Lecture Hall

Abstract

Stable isotopologues of water (HDO and H218O) are widely used to trace the processes in hydrological cycle, as well as to reconstruct paleoclimate. In India, due to the lack of sufficient observation, the spatial and temporal variability of stable isotopologues of water are poorly known. General Circulation Models (GCM) fitted with stable isotope physics are widely used to understand the processes influencing the distribution of stable isotopologues of water. A 32 year long simulation from an isotope enabled GCM (IsoGSM) is compared with the available observations over India and will be discussed in the talk.

Unifying inflation with dark energy a la quintessential inflation

Date: 2014-08-04
Speaker: Prof. M. Sami
Venue: Room No. 469

Abstract

PRL Optical Polarimeters

Date: 2014-07-31
Speaker: Dr. Shashikiran Ganesh, PRL
Venue: Room # 113 (Thaltej Campus)

Abstract

PRL's photo-polarimeter has been in use for nearly 3 decades and has seen a lot of changes in acquisition technology since the initial days. The last upgrades and developments will be discussed and some results presented. In addition to the photo-polarimeter we have recently developed two imaging polarimeters using EMCCD cameras as detectors. One of these is being used on the 0.5m CDK telescope while the other is being developed for use on the 1.2m telescope. Both these new instruments use different approaches to polarization measurement and I shall describe the respective setups and principles of operation. Some lab characterization carried out and results from test observing runs will be presented.

Simple models for structure, folding, and aggregation of proteins

Date: 2014-07-30
Speaker: Prof. Chin-Kun Hu,
Venue: Room No. 469

Abstract

The objective of statistical physics is to understand macroscopic behavior of a many-body system from the interactions of the constituents of that system. In the development of science, simple models have often been used to describe complex systems consisting of many components, e.g. the critical behavior of gas-liquid systems can be well described by the three dimensional Ising model and the Lennard-Jones system. In this talk, I briefly review some results from simple models for structures, folding, and aggregation of proteins. The last problem is related to neurodegenerative diseases. It is pointed out that in many cases, protein aggregation does not result from protein mis-folding. A potential drug from Chinese herb is found for Alzheimer's disease.

An ordered anarchy from a 5D SO(10)

Date: 2014-07-28
Speaker: Dr. Ketan Patel
Venue: Room No. 469

Abstract

The anarchical (structureless) Yukawa approach to understand the fermion masses and mixing angles will be described in a unified theory. Different hierarchies among the quarks and leptons result from the different localization of their 5-dimensional wave-function profiles which arise due to SO(10) breaking in the extra-dimension. Taking suitable scalar sector it is shown that the observed patterns of fermion masses and mixing angles can be well understood in terms of finite number of random structureless Yukawa couplings of order unity. Various aspects of the model construction and phenomenological results will be discussed.

Non-linear Nyquist theorem: A conjecture

Date: 2014-07-24
Speaker: Navinder Singh
Venue: Room No. 469

Abstract

We conjecture "a non-linear Nyquist theorem" for the first time. Our conjecture is based upon tests of the conjectured relation in specific systems in the thermodynamical limit. Nyquist theorem (that relates fluctuations with admittance) is a cornerstone in non-equilibrium statistical mechanics and is an example of the general class of relations called the fluctuation-dissipation theorem. In linear systems it is proved in its generality in a beautiful piece of work by Callen and Welton (in 1950s) . It states that r.m.s. value of fluctuations (in equilibrium) is proportional to the integral of linear admittance (non-equilibrium). We conjecture--with an explicit quantum mechanical calculation of non-linear admittance and fluctuations--that higher moments of the fluctuations bear a similar relation to {\it non-linear} admittance. Thus one can in principle compute non-linear admittance from the character of fluctuations--a relation that should have great practical applicability, for example, for electronic devices that operate under non-linear response.

18-O depletion in monsoon rain relates to large scale organized convection rather than the amount of rainfall

Date: 2014-07-22
Speaker: Ms. Lekshmy P. R.
Venue: Ground Floor Lecture Hall

Abstract

Oxygen isotopic variations in rainfall proxies such as tree rings and cave calcites from South and East Asia have been used to reconstruct past monsoon variability, mainly through the amount effect: the observed 18-O depletion of rain with increasing amount, manifested as a negative correlation of the monthly amount of tropical rain with its delta-948;18-O both measured at the same station. This relation exhibits a significant spatial variability, and at some sites (especially North-East and peninsular India), the rainfall proxies are not interpretable by this effect. We show here that relatively higher 18-O-depletion in monsoon rain is not related necessarily to its amount, but rather, to large scale organized convection. Presenting delta-18-O analyses of ~654 samples of daily rain collected during summer 2012 across 9 stations in Kerala, southern India, we demonstrate that although the cross correlations between the amounts of rainfall in different stations is insignificant, the delta-948;18-O values of rain exhibit highly coherent variations (significant at P = 0.05). Significantly more 18-O-depletion in the rain is caused by clouds only during events with a large spatial extent of clouds observable over in the south eastern Arabian Sea.

Aerosol properties and radiative effects over urban region

Date: 2014-07-21
Speaker: Mr. Ashimananda Modak
Venue: Ground Floor Lecture Hall

Abstract

Atmospheric aerosols perturb Earth's radiation budget through their interaction with solar radiation (direct effect) and clouds (indirect effect) and give rise to radiative forcing. Aerosol radiative forcing continues to contribute the largest uncertainty to the total radiative forcing estimate. The uncertainty is caused by the spatio-temporal heterogeneity in sources, characteristics, and residence times. Anthropogenic aerosols dominate in urban regions due to industrial and vehicular emissions. However, meteorology and long range transport of aerosols such as dust and sea salt can influence the characteristics of urban aerosols and modulate their properties. Therefore, aerosol properties are expected to undergo a strong seasonal variation over urban regions. In the seminar, results obtained over Ahmedabad from the simultaneous observations of spectral aerosol optical depth, single scattering albedo and aerosol phase function using Sun/sky radiometer will be presented and discussed.

Instabilities in Anisotropic Chiral Plasmas

Date: 2014-07-21
Speaker: Avdhesh Kumar
Venue: Room No. 469

Abstract

Kinetic theory can be applied to understand variety of many body problems arising in various branches of physics. This, however leaves out an important class of phenomena requiring triangle anomaly. Recently Son and Yamamoto have developed a modified kinetic theory that incorporate triangle anomalies and the chiral magnetic effect (CME) by taking into account Berry phase. They show that modified kinetic theory gives the identical results for the parity odd correlation function as computed from the perturbation theory in the next to leading order hard dense loop approximation. Using this modified kinetic theory in presence of the chiral imbalance the collective modes in the quasi-static limit were analyzed and found to be unstable. However in many realistic situations in condensed matter physics and in plasma physics it is important to consider equilibrium distribution function to be anisotropic in the momentum space. In this seminar I shall discuss modified kinetic theory to consider anisotropic chiral plasma and how even a small anisotropy can modify the chiral imbalance instability. I shall also discuss when a stream of charged particle travel in a thermally equilibrated isotropic chiral plasma may lead to a instability.

Discussion on symmetry followed by interaction session

Date: 2014-07-18
Speaker: Prof. Ashok Das
Venue: USO Seminar Hall

Abstract

Equation-of-motion coupled-cluster method and its application to probe variation in the fine structure constant

Date: 2014-07-17
Speaker: Dillip Nandy
Venue: Room No. 469

Abstract

To answer the speculated concept of possible temporal variation of the fine structure constant (alpha), precise observations of the absorption lines in astrophysics are vital. These observational results in combination with accurately calculated sensitivity coefficients for the variation of the fine structure constant in the atomic energy levels can put stringent constraint on the variation of alpha. In this talk, I shall highlight some evidences on the variation of alpha from the astrophysical observations and compare them with the results obtained from the atomic clock experiments. For further investigations, we propose consideration of new astrophysical interesting candidates with enhanced alpha variation effects to extract out these information more convincingly. We have developed a relativistic coupled-cluster method in the equation-of-motion framework to perform the corresponding calculations which will be briefly discussed.

Silicon isotopic approach for the paleoclimatic reconstruction in the northern Indian Ocean

Date: 2014-07-15
Speaker: Ms. Chandana K. R
Venue: Ground Floor Lecture Hall

Abstract

The drop in atmospheric CO2 during glacial periods has been interpreted as sequestration of CO2 in the deep oceans. Another theory supporting the drop in atmospheric CO2 concentrations is consumption of nutrients by phytoplankton during glacial period. The biogeochemical cycling of silicon in the ocean is controlled by diatom production. The silicon isotopic composition of the diatom / biogenic opal can help in reconstructing the nutrient utilisation patterns and test the hypothesis of atmospheric CO2 drop during glacials. The silicon isotope can be used to ascertain the silicic acid utilization by the diatoms on a regional scale over glacial and interglacial cycles of the Quaternary period. The northern Indian Ocean being the most dynamic region which experiences seasonal monsoon, high biological productivity resulting in extreme oxygen minimum zone has attracted great attention. Few studies from Southern ocean based on silicon isotope have revealed that under iron stressed conditions, diatoms shows enrichment in delta30Si which implies a greater fraction of nutrient utilisation. In the tropical region such as the northern Indian Ocean where iron limitation is not a constraint, behaviour of silicon isotope as a function of nutrient utilisation pattern during the glacial and interglacial cycles in sediments still needs to be realised.

Gauge dependence of the fermion mass: Part 2

Date: 2014-07-15
Speaker: Prof. Ashok Das
Venue: Room No. 469

Abstract

Optical investigations of wave dynamics in the daytime upper atmosphere

Date: 2014-07-14
Speaker: Mr. Deepak Kumar Karan
Venue: Ground Floor Lecture Hall

Abstract

Upper atmospheric behaviour (in terms of compositional, density, temperature variations) is a superposition of plasma and neutral dynamical changes that occur over a large range of time scales - from a few minutes to several days. Optical method of investigations are one of the effective means to study the neutral dynamical behaviour of the upper atmosphere. Such optical investigations over long durations (order of several tens of days) are possible using daytime optical measurements. However, these measurements pose a great challenge as the solar scattered background continuum overwhelms the daytime airglow emission intensities. In this talk techniques will be described that have overcome this difficulty and preliminary results will be presented on the neutral wave dynamics in the upper atmospheric regions. These optical dayglow measurements have been obtained over several months in this year from PRL's optical aeronomy observatory situated at JNTU campus in Hyderabad.

Gauge dependence of the fermion mass: Part 1

Date: 2014-07-14
Speaker: Prof. Ashok Das
Venue: Room No. 469

Abstract

Hard X-ray polarimetry with Astrosat-CZTI – a new window in Astrophysics about to open?

Date: 2014-07-10
Speaker: Mr. Tanmoy Chattopadhyay, PRL
Venue: Room # 113 (Thaltej Campus)

Abstract

Astrosat is the forthcoming Indian satellite dedicated for astronomical studies. CdZnTe Imager (CZTI), one of the five instruments in Astrosat, is a pixelated spectroscopic instrument sensitive in 20-150 kev range. Because of its pixilation nature and significant Compton scattering efficiency at energies beyond 100 kev, it’s possible to measure polarization in X-rays exploiting the Compton scattering technique at energies beyond its primary energy range. In this talk, I will explain the simulation and experimental results which clearly show that the flight configuration of Astrosat-CZTI will be capable of polarisation measurement in hard X-rays and perhaps going to be the most sensitive polarimeter in the sky. This is the first ever experimental demonstration of the concept of doing Compton polarimetry by pixelated CZTI detectors. One of the main science goals of CZTI as a polarimeter is to differentiate various possible emission mechanisms in black hole sources in hard X-rays. In this talk, I will explain these processes and the possibility of constraining them by the fourth parameter of radiation.

Understanding the distributions of dissolved iron in the Northern Indian ocean

Date: 2014-07-08
Speaker: Mr. Venkatesh Chinni
Venue: Ground Floor Lecture Hall

Abstract

Storm-substorm relationship: a case study

Date: 2014-07-07
Speaker: Mr. Diptiranjan Rout
Venue: Ground Floor Lecture Hall

Abstract

Geomagnetic storms are the perturbations in the geomagnetic environment of the earth primarily under the influence of the southward interplanetary magnetic field (IMF Bz). On the other hand, substorms are the magnetospheric disturbances in which the stored energy in the magnetotail is released. Changes in the solar wind parameters like southward turning of IMF Bz, enhancement in the solar wind ram pressure etc. can trigger substorms. The relationship between storm and substorm is complex. In the present talk, an attempt will be made to highlight a few aspects of these complexities based on the observational data.

Fluctuation and interaction induced instability of dark solitons in single and binary condensates

Date: 2014-07-03
Speaker: Arko Roy
Venue: Room No. 469

Abstract

In this talk, we shall discuss about the stability of dark soliton in single and two-species Bose-Einstein condensates. We will show that the presence of soliton in a single-species condensate enhances the quantum depletion of the ground state which is sufficient enough to induce dynamical instability of the solitons in the condensate. On the other hand, for two-species condensates, in addition to the third Goldstone mode that emerges at higher interspecies interaction, due to the presence of the soliton in one of the components, a fourth Goldstone mode also arises. We use Hartree-Fock-Bogoliubov theory with Popov approximation to examine the mode evolution and demonstrate for specific values of interspecies interaction, when the anomalous mode collides with a higher energy mode it renders the solitonic state oscillatory unstable.

Chronology and geochemistry of dry land fluvial system, western India.

Date: 2014-07-01
Speaker: Dr. Anil D. Shukla
Venue: Ground Floor Lecture Hall

Abstract

Dry land fluvial system in western India emanates from the Aravalli ranges and drains into the Gulf of Cambay and the Gulf of Kachchh. The sedimentary characteristics and textural attributes of the incised alluvial sequences in various river basins of western Indian indicate significant variability in the palaeohydrological conditions. Considering that the region is dominated by the Indian Summer Monsoon (ISM), the temporal changes in sedimentation pattern can be ascribed to the changing strength of the ISM. In the present study, we investigated the Banas River which drains through the transitional climatic zone viz. the arid northwest and semi-arid southeast.

The propagation of an optical vortex pair through an astigmatic optical system

Date: 2014-06-30
Speaker: Mr. Salla Gangi Reddy
Venue: Ground Floor Lecture Hall

Abstract

Optical vortices are dark spots under bright background. These beams have a phase jump of 2*pi*l around its center, l is being its topological charge. Optical vortices have orbital angular momentum of (lh/2*pi) per photon. Here, we will discuss about the propagation of vortex pair embedded in host Gaussian beam through an astigmatic optical system i.e. tilted lens. We also discuss how this study has been utilized to find the individual charges and net charge present in the beam.

Stokes profile inversion technique

Date: 2014-06-30
Speaker: Rahul Yadav
Venue: USO Seminar Hall

Abstract

Inversion techniques are the most powerful and sophisticated tool to infer the information about the solar magnetic field and the thermodynamic properties from the spectral line and Stokes profiles.They are based on non-linear fitting of the synthesized stokes profiles with the observed ones, generally using the Levenberg-Marquardt algorithm. We are developing an inversion code to solve the polarized radiative transfer equations. The code assumes that the properties of solar atmosphere are well described by the Milne-Eddington atmosphere. In this talk, I will share my understanding about the implementation of inversion techniques and specifically discuss the synthesis of Stokes profiles.

Status of 8-fold degeneracy after theta_13 discovery

Date: 2014-06-30
Speaker: Newton Nath
Venue: Room No. 469

Abstract

Standard 3-flavor neutrino oscillations depend on 6-oscillation parameters, namely 3-mixing angles(theta_13, theta_12, theta_23 ), 2-mass squared differences (Delta_m^2_21, Delta_m^2_31) and 1 CP - phase (delta_cp). In 1990s neutrino oscillations phenomenon were confirmed by different neutrino experiments like SK, SNO indicating that neutrinos do possess non-zero tiny mass. Today neutrino physics has reached an era of precision measurement. In this talk, I will discuss different parameter degeneracies present in the neutrino oscillation probability, collectively called 8-fold degeneracy. Muon neutrino survival probability (P_mu_mu) is sensitive to sin^2(2 theta_23) and sin^2(Delta_m^2_31 L/4E) this leads to two degeneracies, whether theta_23 is < 45^0 or > 45^0 and Delta_m^2_31>0 or <o. 8-fold degeneracy is due to (theta_13, delta_cp) , (hierarchy, delta_cp) and the octant degeneracy of theta_23. Reactor experiments like Double CHOOZ, Daya Bay, RENO have determined non-zero value of theta_13 upto 10 sigma level and the current global best fit value of theta_13 is around 8.8^0. Such a large mixing angle resolves the (theta_13, delta_cp) degeneracy. In this talk I will discuss how Long Baseline Experiments can help to resolve those degeneracies, especially in the context of large theta_13.

M dwarfs in Eclipsing Binary Systems

Date: 2014-06-27
Speaker: Ms. Priyanka Chaturvedi, PRL
Venue: Room # 113 (Thaltej Campus)

Abstract

Despite copious number of M dwarfs present in our galaxy, masses and radii for these stars are still not determined at higher accuracies, primarily due to their fainter magnitudes in visible band. Radii for stars less massive than Sun are known to be 10% smaller theoretically than observed and temperatures are 5% higher. It is suggested that strong magnetic fields inhibit convection, which causes these stars to inflate. In general M dwarfs form an interesting area for stellar astronomers. We have observed few M dwarfs in eclipsing binary systems as companions to brighter stars. I will be discussing the techniques and some preliminary results obtained after studying these systems.

Evidence for leptonic CP phase from NOVA, T2K and ICAL

Date: 2014-06-26
Speaker: Monojit Ghosh
Venue: Room No. 469

Abstract

The phenomenon of neutrino oscillation is now well understood from the solar, atmospheric, reactor and accelerator neutrino experiments. This oscillation is characterized by a unitary PMNS matrix which is parametrized by three mixing angles and one phase known as the leptonic CP phase. Though there are already significant amount of information about the three mixing angles but the CP phase is still unknown. In my talk I will describe the synergy between the long-baseline (LBL) experiment NOVA, T2K and the atmospheric neutrino experiment ICAL@INO for obtaining the first hint of CP violation in the lepton sector.

Understanding the Neoproterozoic Earth

Date: 2014-06-24
Speaker: Mr. Bivin Geo George
Venue: Ground Floor Lecture Hall

Abstract

Proterozoic Eon (2500 – 541 Ma) in the Earth’s history is marked by significant chemical, biological and geological events such as the oxygenation of the atmosphere, evolution of multi-cellular life, assembly and breaking up of the supercontinent Rodinia and at least three global glaciations. The end of this Eon, known as the Neoproterozoic Era (1000-541 Ma), witnessed some of the most important events in the Earth history: e.g., the snowball Earth and the first appearance of animal life. In this talk I shall deal with some of these events that had permanently changed the surface of the Earth and the chemical/geological evidences that teach us about the timing and extent of such events. I shall also discuss where in India one can find such evidences and how these can be studied to understand the Neoproterozoic Earth.

X-Ray/UV/Opt correlations in Seyfert Galaxies in the view of Disk-Coronae connections, a case study of NGC 4395

Date: 2014-06-19
Speaker: Dr. Sunil Chandra, PRL
Venue: Room # 113 (Thaltej Campus)

Abstract

The Seyferts or Seyfert Galaxies are a subclass of Active Galactic Nuclei (AGNs). These are well known to show emission dominant spectra unlike the typical stellar spectra. Based on the presence and absence of broad emission lines in their optical spectra, these galaxies are sub-classified in two branches 1) Type-I and 2.) Type-II. The strong emission lines show that our line of sight is far off to the relativistic jet. The major source of emission in Seyferts is the disk emission. The disk emission when interact with the violent gas revolving around the central engine give rise to strong emission lines. These regions are termed as line emission regions (namely BLRs & NLRs). On the other hand the disk emission when reprocessed by hot tenuous corona give rise the major X-ray emission. These object show the variability in flux over a range of frequencies. However, The origin of UV/Opt variability in AGNs is still under debate. Two well accepted physical mechanisms explaining these are (i) reprocessing of X-ray emission by the accretion disc and (ii) intrinsic variations of the thermal disk emission. Therefore, correlations in the X-Ray and UV/Opt variability may provide a better clue about the physics at work. In this talk I will be briefing about the general properties of Seyferts, geometry and current understanding of physical processes responsible for emission. The preliminary results of our collaborative work shows a supportive evidence of reprocessing model.

Impact of perturbative QCD corrections on neutrinoless double beta decay

Date: 2014-06-19
Speaker: Namit Mahajan
Venue: Room No. 469

Abstract

I'll discuss perturbative QCD corrections and evolution under renormalization group for neutrinoless double beta decay, both for the short and long range parts.

Infrared properties of cuprates in the pseudogap state: A study of Mitrovic-Fiorucci and Sharapov- Carbotte scattering rates

Date: 2014-06-17
Speaker: Pankaj Bhalla
Venue: Room No. 469

Abstract

The frequency dependent scattering rate of generalized Drude model contains important physics on the electronic structure and on scattering mechanism. In this talk, we will discuss the frequency dependent scattering rate of cuprates (Mitrovic-Fiorucci/ Sharapov-Carbotte scattering rate) in the pseudogap phase using the non-constant energy dependent Yang-Rice-Zhang (YRZ) density of states. We will see the problems observed with traditional approach in the behavior of scattering rate and how our approach has sorted these issues. We will also discuss the experimental results of behavior of scattering rate and qualitative agreement of our results with them.

Left-right symmetry and the charged Higgs bosons at the LHC.

Date: 2014-06-12
Speaker: Gulab Bhambhaniya
Venue: Room No. 469

Abstract

Left-right symmetric models explain spontaneous violation of parity, which is ad-hoc in the Standard Model (SM). Along with this, LR symmetric models also provide light neutrino masses naturally. In this talk, we consider Minimal Manifest Left-right symmetric model (MLRSM) at TeV scale. We will focus on the charged Higgs boson sector of the model, in the context of LHC discovery search for beyond SM physics. Effects of charged scalars at colliders depend on their masses. Smaller the masses, larger effects are expected. But then the question is how small their masses can be, keeping the parity breaking scale large? Using the experimentally measured mass of the SM-like Higgs boson, experimental bounds on parity breaking scale and constraints due to the flavor changing neutral current (FCNC) effect, we analyzed the spectra of the charged scalars. The production of charged Higgs bosons and decay of these lead to multilepton signals at the LHC. Background and signals are analyzed with suitable kinematic cuts. We provide some benchmark points where simulations are done to make a realistic estimation of the signal events over the SM backgrounds. We will also discuss the impact of the charged scalars in the Higgs to di-photon decay rate .

Universal Extra Dimension with Boundary Localised Terms

Date: 2014-06-11
Speaker: Ujjal Kumar Dey
Venue: Room No. 469

Abstract

In this talk I'll briefly describe the universal extra dimensional (UED) model in the presence of boundary localised terms (BLT). In UED, conserved discrete symmetry, KK parity, leads to a stable particle in the spectrum and that can be a good dark matter candidate. The mass spectrum as well as the couplings of the model depends on these BLTs. I'll be discussing the novel features that arise on the plain UED after the inclusion of these BLTs. Constraints coming from recent collider and dark matter observations will also be discussed.

Silicon isotopes in meteorites: implication to planetary core formation

Date: 2014-06-06
Speaker: Ms. Jinia Sikdar
Venue: Room #114 (Thaltej campus)

Abstract

Silicon isotopes in meteorites: implication to planetary core formation

Date: 2014-06-06
Speaker: Ms. Jinia Sikdar
Venue: Room #114 (Thaltej campus)

Abstract

Copositivity and boundedness of the scalar potential

Date: 2014-06-05
Speaker: Tanmoy Mondal
Venue: Room No. 469

Abstract

There are experimental evidences that conclude that SM cannot be a complete theory of nature. Thus one needs to look for BSM physics. The BSM scenarios that include many scalar fields contain scalar potential with large number of quartic couplings. Due to the complicated structures of such scalar potentials it is indeed difficult to adjudge the stability of the vacuum. Thus one needs to formulate a proper prescription to compute the vacuum stability criteria. In this talk i will discuss the idea of copositive matrices to deduce the conditions that guarantee the boundedness of the scalar potential. As this idea is based on the mathematical arguments it evades the ambiguities while finding the stability criteria in the earlier used methods. It is also interesting to note that the copositive criteria allows us to find the stability conditions with larger parameter space.

Kinematic evolution of CMEs in the heliosphere

Date: 2014-06-02
Speaker: Wageesh Mishra
Venue: USO Seminar Hall

Abstract

Coronal Mass Ejections (CMEs) are the potential drivers of many space weather events and the estimation of their arrival time near 1 AU is a crucial problem for a solar-terrestrial physicist. Since the discovery of CMEs, several methods have been developed to estimate their arrival time, mainly using the coronagraphic observations near the sun or using empirical, statistical or numerical MHD models. Before the era of heliospheric imagers, studies were limited to use of only two point observations of CMEs, one near the Sun as remote sensing observations and other near the Earth viz. in situ observations. Such studies are not sufficient for accurate arrival time prediction of CMEs. In this talk, I will first revisit the physics of appearance of a CME and some inherent difficulties in reliably estimating its kinematics and arrival time.Then, I will show how continuous tracking of CMEs from near the Sun to the Earth and beyond, is possible using J-maps constructed from SECCHI/STEREO images. I will show, in order to understand the propagation of CMEs, we have estimated their kinematics by implementing the geometric triangulation technique. The estimated kinematics is used as input to the drag based model of CME propagation for the distance where CMEs could not be tracked unambiguously. This approach improves the estimation of the arrival time as well as the transit velocity of a CME at 1 AU. In the end, I will emphasize that use of kinematics (even deprojected, i.e. 3D) of CMEs, estimated in coronagraphic field-of-view is often not sufficient for accurately predicting their arrival time near the Earth.

U, Th and K measurements using gamma rays from Mercury: Implications for formation and evolution

Date: 2014-05-30
Speaker: Dr. D. Banerjee
Venue: Room #114 (Thaltej campus)

Abstract

U, Th and K measurements using gamma rays from Mercury: Implications for formation and evolution

Date: 2014-05-30
Speaker: Dr. D. Banerjee
Venue: Room #114 (Thaltej campus)

Abstract

Presolar Grains: Starbits in the laboratory

Date: 2014-05-23
Speaker: Mr. Lalit Kumar Shukla
Venue: Room #114 (Thaltej campus)

Abstract

Presolar Grains: Starbits in the laboratory

Date: 2014-05-23
Speaker: Mr. Lalit Kumar Shukla
Venue: Room #114 (Thaltej campus)

Abstract

Preliminary results from the development of Gamma ray Spectrometer

Date: 2014-05-16
Speaker: Mr. DipakmKumar Panda
Venue: Room #114 (Thaltej campus)

Abstract

Preliminary results from the development of Gamma ray Spectrometer

Date: 2014-05-16
Speaker: Mr. DipakmKumar Panda
Venue: Room #114 (Thaltej campus)

Abstract

Large relative motion observed between three different cosmic reference frames: Is the cosmological principle in jeopardy?

Date: 2014-05-15
Speaker: Dr. Ashok K. Singal, PRL
Venue: Room # 113 (Thaltej Campus)

Abstract

The peculiar velocity of the solar system relative to the CMBR reference frame has been determined to be 369 km/s. However, the velocity relative to the frame of 1.8 million distant radio sources, was found by us to be approximately in the same direction but with a magnitude about 1600 km/s, a result later corroborated by two independent groups. With an aim to hopefully resolve this controversy of two different velocity magnitudes, we have investigated anisotropy in the redshift distribution of distant quasars. For this purpose we have used the latest SDSS catalogue comprising 166583 quasars with reliable accurate redshift measurements. Quite unexpectedly, our results yield the magnitude of the peculiar velocity to be 9750+_550 km/s (~3% the speed of light), ~6 times the NVSS value and as much as a factor of ~25 or so larger than the CMBR value. Even more surprising, the motion is found to be in a direction nearly opposite to that found from CMBR and NVSS. The large differences in the magnitudes of inferred motion as well as their opposite signs are rather disconcerting. A genuine difference between these three velocity vectors would imply highly anisotropic Universe, with anisotropy changing with epoch. This would jeopardize the cosmological principle where the isotropy of the Universe is assumed for all epochs, and without which presently there is hardly any cosmological model.

Tidal Chain Reaction

Date: 2014-05-12
Speaker: Dr. Bhalamurugan Sivaraman
Venue: Ground Floor Lecture Hall

Abstract

Origin of life has numerous hypothesis. However, the making of precursor molecules, essential for forming a DNA in the colder molecular factories deep in space, had gained support, backed by laboratory simulations. Though formed under such conditions and delivered to a habitable environment, the amplification of these molecules yet remains unanswered. A hypothesis, Tidal Chain Reaction, proposed towards the amplification of "molecules of life" under early Earth conditions will be discussed.

Signature of Gibbons-Hawking temperature in the BICEP2 measurement of gravitational waves

Date: 2014-05-12
Speaker: Akhilesh Nautiyal
Venue: Room No. 469

Abstract

BICEP2 has detected gravitational waves with large tensor to scalar ratio r=0.2, that is in tension with PLANCK's upper bound r<0.11 from temperature anisotropy. The tension can be resolved if the spectrum of gravitational waves is blue tilted. As the standard inflationary models can not generate blue tilted spectrum, this may be a consequence of Hawking radiation seen by static observer inside the de Sitter Horizon. In this talk, after briefly discussing CMB polarization, we will discuss the signature of Hawking radiation on B-modes and its implications for BICEP2 and PLANCK.

Chemistry on the Surfaces of Micro and Macro Icy Bodies

Date: 2014-05-08
Speaker: Dr. Bhalamurugan Sivaraman, PRL
Venue: Room # 113 (Thaltej Campus)

Abstract

Condensed molecular species are prevalent in many astrophysical environments including surfaces of dust grains in the interstellar medium, on planetary surfaces in our solar system, as icy aerosols in planetary atmospheres and in comets. These regions are pervaded by ion, photon and electron collisions that are believed to be responsible for the chemistry in synthesizing variety of molecules. Energetic particles alter the molecular composition of these ices and generate new complex species as inferred through the observation of over 180 molecular species in interstellar and circumstellar media. Recent findings from the space and ground based observations on the signatures of several new molecules reveal complex chemistry that is yet least understood under the conditions that are unique to the cold dust in the interstellar medium and icy satellites of our solar system. Such conditions are simulated in the laboratory (in PRL and elsewhere) and the chemistry that underpins such complex molecular synthesis is being explored. In this discussion, we will briefly look into the experimental details along with few results and its implications to the micro and macro icy bodies.

Seeing what we hear: finding electromagnetic counterparts for gravitational wave sources

Date: 2014-05-01
Speaker: Dr. Varun Bhalerao
Venue: Room # 113 (Thaltej Campus)

Abstract

Within the next decade, a global network of advanced gravitational wave detectors including LIGO-India are expected to detect various gravitational wave sources. These detectors can yield certain parameters of the gravitational wave source, but complementary studies in electromagnetic wavelengths are crucial for a complete astrophysical understanding. In this talk, I will talk about the proposed electromagnetic counterparts of these sources, and the extremely challenging problem of detecting them. I will highlight why India forms a key node in this global effort, and discuss prospects of optical, IR, radio and X-ray follow-up from India.

Hawking Radiation and BICEP2

Date: 2014-05-01
Speaker: Prof. Subhendra Mohanty
Venue: Room No. 469

Abstract

I will summarise the recent result of gravitational wave observation by BICEP2 and its implications for cosmology. I will also survey the notion of Hawking Radiation (HR) and give examples of HR in different physical settings. Finally I will argue that the BICEP2 observations may be seeing a signature of Hawking temperature of the de-Sitter space at the time of Inflation.

Causes and consequences of June 2013 devastation in the Bhagirathi and Alaknanda valleys

Date: 2014-04-29
Speaker: Dr. Navin Juyal
Venue: Ground Floor Lecture Hall

Abstract

During June 15th to 17th 2013, unprecedented devastation engulfed the entire Uttarakhand in general and Alaknanda and Bhagirathi valleys in particular. The disaster was attributed to an integrated effect of heavy rainfall intensity, sudden outburst of a lake (Chorabari) and very steep topographic condition (natural calamity). However, there are suggestions that the magnitude of the tragedy was amplified due to human intervention in the fragile Himalayan ecosystem. The presentation will focus on ascertaining the causes of the June 2013 tragedy with emphasize on how best we can protect the terain and the people from such devastation in future.

Muon anomalous magnetic moment and positron excess at AMS-02 in a gauged horizontal symmetric model

Date: 2014-04-29
Speaker: Gaurav Tomar
Venue: Room No. 469

Abstract

The measurement of muon anomalous magnetic moment shows the discrepancy between the experimental value and the standard model prediction. We studied an extension of the standard model with vector lepton doublets to explain this discrepancy. The neutral components of the 4th generation vector lepton doublets identified as dark matter and can explain the positron excess seen in the AMS-02 experiment. In this talk we will discuss this model in details.

Can the observed CP asymmetry in tau to K pi nu_{tau} be due to Non-Standard Tensor interactions

Date: 2014-04-28
Speaker: Dr. H. Zeen Devi
Venue: Room No. 469

Abstract

The BABAR collaboration has measured that the decay rate asymmetry in the tau decay modes tau to K Pi nu has an opposite sign compared to the SM prediction. In this talk we will try to discuss how such a sign difference can be explained if we assume the presence of some non-standard tensor interaction.

Insights into layered ejecta craters on Mars

Date: 2014-04-25
Speaker: Dr. S. Vijayan
Venue: Room #114 (Thaltej campus)

Abstract

nsights into layered ejecta craters on Mars

Date: 2014-04-25
Speaker: Dr. S. Vijayan
Venue: Room #114 (Thaltej campus)

Abstract

Steady decline in solar polar magnetic fields and heliospheric solar wind micro-turbulence levels: Are we headed towards a Maunder minimum?

Date: 2014-04-24
Speaker: Dr. Susanta K. Bisoi
Venue: Room # 113 (Thaltej Campus)

Abstract

Sunspots or dark regions of strong magnetic fields on the sun are generated via magneto-hydrodynamic processes that involve the cyclic generation of toroidal fields (sunspot fields) from pre-existing poloidal fields and the eventual regeneration of the poloidal fields. This cyclic process, referred to as the solar dynamo, leads to the well known solar activity cycle of waxing and waning sunspot numbers with a period of 11 years. The sunspot minimum at the end of solar cycle 23 was, however, one of the deepest recorded in the past 100 years, with cycle 24 starting about 16 months later than expected. A detailed study of solar high latitude (>45o) or polar magnetic fields using ground based magneto-grams has clearly shown a steady decline in polar field strength since mid-1990's which has continued to the present, i.e. until the end of February 2013. Since sunspot fields are generated from polar fields, this long term decline in polar field strength would eventually effect the sunspot field strength in the subsequent solar cycles. A continued decline in the polar fields in this manner would imply that the polar field strength will approach zero by ~2031. In addition, a detailed analysis of solar wind micro-turbulence in the inner heliosphere has also shown a steady decline in sync with the declining solar photospheric magnetic fields. The fact that both solar polar fields and inner-heliospheric micro-turbulence levels show a similar decline raises the question as to whether we are headed towards an extended period of very little or no sunspot activity in a manner similar to what was seen in the Maunder minimum?

Class of Higgs-portal Dark Matter models in the light of gamma-ray excess from Galactic center

Date: 2014-04-24
Speaker: Dr. Tanushree Basak
Venue: Room No. 469

Abstract

Recently the studies of anomalous gamma-ray emission in the Fermi-bubbles have drawn a lot of attention as it points out that the excess of ~ 1-3 GeV gamma-ray in the low latitude is consistent with the emission expected from annihilating dark matter. The best-fit to the gamma-ray spectrum corresponds to dark matter candidate having mass in the range ~ 31-40 GeV annihilating into b-bbar pair with cross-section ~ (1.4 - 2.0) x 10^(-26) cm^3 s^(-1). In this talk, we will discuss a class of Higgs-portal dark matter models, in presence of scalar resonance, which are well-suited for explaining these phenomena. We will also comment on a few Higgs-portal models which are found to be incompatible with the recent analysis.

Dissolved silicon and its isotopes in water column of the Bay of Bengal: Internal cycling versus lateral transport.

Date: 2014-04-22
Speaker: Dr. Satinder Pal Singh
Venue: Ground Floor Lecture Hall

Abstract

Contribution of Oceans in Atmospheric Studies of Cyclones and Monsoons

Date: 2014-04-21
Speaker: Dr. M. M. Ali
Venue: Ground Floor Lecture Hall

Abstract

Prediction of atmospheric phenomenon like monsoons and cyclones has been a challenging problem for many years. While efforts are under way to improve the understanding of the physics of the problem of track and intensity prediction of cyclones and rainfall during monsoon, it is worthwhile to re-look at the efficiency of the input parameters presently used in models and to look for new approaches. Sea surface temperature (SST) is one such parameter that needs to be re-considered. This parameter is the only oceanographic input used in most of the statistical and dynamical prediction models, though it is well recognised that ocean-atmosphere is a coupled system and the atmosphere interacts with the upper layer of the ocean, not just with the surface alone represented by SST. Although the upper ocean drives SST depending on mixed layer depth and upper ocean salinity, in many cases SST does not represent the energy available to the atmospheric processes or the ocean heat content (OHC). This presentation highlights that satellite-derived SST (a skin temperature) is not a good indicator for cyclone and monsoon studies. It suggests a more accurate parameterization of SST, for example, a parameter that also depends upon OHC. The possibility of using ocean mean temperature, representing the thermal energy of the upper ocean available to the atmosphere, in the monsoon and/or cyclone models is one of the main aims of this presentation.

Effective model study of low lying scalar mesons and Chiral phase transition

Date: 2014-04-17
Speaker: Dr. Tamal K. Mukherjee
Venue: Room No. 469

Abstract

In the framework of linear sigma model we study the effect of mixing between effective quarkonium and tetraquark as well as scalar glueball fields on the composition of low lying scalar meson (with mass below 2 GeV) and its implication to the chiral phase transition. Based on our study we will comment on what may be the mass of the lowest possible scalar and pseudoscalar glueball states. We will also discuss on what may be the nature of the sigma or f0(600) meson. With respect to the chiral phase transition we find the physical mass spectrum of mesons put a tight constraint on the parameter set of our model. We find a sufficiently strong cubic self interaction of the tetraquark field can drive the chiral phase transition to first order even at zero quark chemical potential. Weak or absence of the cubic self interaction term of the tetraquark field make the chiral pahse transition crossover at vanishing density.

PRL Imaging Polarimeter - observations and first results

Date: 2014-04-10
Speaker: Mr. Ashish Mishra
Venue: Room # 113 (Thaltej Campus)

Abstract

Polarization study in astronomy plays a vital role in exploring astronomical domain starting from our solar system to cosmic beginnings. An imaging polarimeter is being developed in PRL. I will discuss the instrument working principle and the related optics. Data reduction and analysis procedures were developed in python and I will present the algorithms. The calibration of the instrument has been verified for 100% polarization using a glan prism on various stars. Polarization measurements of standard stars are also well matched with those in the literature. Many galactic and extra-galactic sources were observed during a couple of observing runs. For my project I have studied Carbon stars which possess attributes due to which there exists a net intrinsic polarization. Some results will be presented.

Predicted Concentrations of OF CH4 ,H2O and O3 for the Arrival MOM at MARS

Date: 2014-04-07
Speaker: Mr. Gaurav Seth
Venue: Ground Floor Lecture Hall

Abstract

India launched its first interplanetary mission to Mars called the Mars Orbiter Mission (MOM) on 5th November 2013 which would be reaching Mars approximately on 24th September 2014. It is carrying a Methane Sensor whose objective is to measure the concentration of CH4 in the atmosphere of Mars. The concentration of CH4 is predicted at low latitude region where presence of CH4 has been reported by MGS and Mars Express. We have also estimated concentrations of O3 and H2O in the Martian atmosphere in this region. HITRAN database is used for our calculations. Estimated results of the concentrations of CH4, O3 and H2O for the arrival of MOM at Mars will be presented in the seminar.

Numerical Simulation of MHD Waves in the Solar Atmosphere

Date: 2014-04-07
Speaker: Prof. Robert von Fay
Venue: Room No. 469

Abstract

Photospheric motions, such as granular buffeting or vortices at the foot-point of magnetic flux tubes, could excite MHD waves, which propagate upwards though the solar atmosphere towards corona. In this talk I will show the results of 3D numerical simulation of generation and propagation of slow/fast magnetoacoustic and torsional Alfven modes in the localised waveguides and determine the energy flux they carry along the magnetic field lines. Also, the new analytical approach in construction of a system of multiple magnetic flux tubes, for example, pair of open tubes and complex mixed open tube configurations with curvature and asymmetry, will be discussed. This method provides an opportunity to build a range of analytical models of magnetic field configurations that will most realistically capturing magnetic structures of the lower solar atmosphere. About the speaker: Prof. Robert von Fay-Siebenburgen (Robertus) is the Director of Research at the School of Mathematics and Statistics at the University of Sheffield, UK. Prof. Robertus? group has a very high international reputation in the field of theoretical solar physics with particular expertise in the heating processes that generate and sustain the observed high temperature of the solar atmosphere by using both numerical and exact analytical methods and through observational studies using joint ground-based and satellite missions.

Search for new physics in the multijet and missing transverse momentum at CMS

Date: 2014-04-03
Speaker: Dr. Seema Sharma (CMS Collaboration)
Venue: Room No. 469

Abstract

An inclusive search for new physics is performed in multijet events with large missing transverse momentum produced in proton-proton collisions at sqrt(s)=8 TeV using a data sample corresponding to an integrated luminosity of 19.5 inverse femtobarns collected with the CMS detector at the LHC. The contribution of standard model processes is estimated using data driven techniques. The observed numbers of events in various search regions are consistent with expected backgrounds. Exclusion limits are presented for several simplified supersymmetric models of squark or gluino pair production. Discussion on SUSY search in multijets+MET final state (hep-ex 1402.4770), and a brief summary of current status of SUSY.

Upper atmospheric dynamics during sudden stratospheric warming events and at varying levels of solar activity

Date: 2014-03-31
Speaker: Mr. Fazlul Laskar
Venue: Ground Floor Lecture Hall

Abstract

The low-latitude upper atmosphere of the Earth is coupled vertically to the lower atmosphere and horizontally to high-latitude through dynamical processes. Waves from the lower atmosphere propagate to the upper atmosphere under suitable background conditions in the intervening medium. The physical properties of the intervening medium are affected by both solar and meteorological parameters. Using observations from daytime airglow emission intensities, equatorial electrojet strength, and total electron content, it has been found that the influence of both shorter and longer period waves on the upper atmosphere is dependent on solar activity level and strength of sudden stratospheric warming events. These findings will be presented in the context of the vertical coupling of the atmospheres.

Non-chiral bosonization of fermions

Date: 2014-03-27
Speaker: Dr. Girish S. Setlur
Venue: Room No. 469

Abstract

In this talk, I describe the ongoing work in our group in recasting interacting fermion theories in a bosonic language with the aim of extracting asymptotically exact single particle Green functions. I describe the recent remarkable closed form expression of the Green function of a Luttinger liquid in presence of a single impurity (Kane Fisher problem). This talk will also introduce the concept of a non-local particle hole creation operator for both boson and fermion systems and point of their applications in computing the correlation functions.

Rabi Oscillations in Graphene

Date: 2014-03-26
Speaker: Dr. Girish S. Setlur
Venue: K.R. RAMANATHAN AUDITORIUM

Abstract

In this talk, the ongoing work in the Rabi oscillation phenomenon, which is well-known in two-level systems and also in semiconductors to probe the low energy band structure of graphene, will be discussed. Specifically, we have predicted and shown experimental confirmation of a peculiar type of Rabi oscillation that is unique to graphene which is seen far from conventional resonance. These anomalous Rabi oscillations are shown to be due to the pseudospin degree of freedom of graphene. We also show that anomalous Rabi oscillations are sensitive to changes in the low-energy band structure of graphene whereas conventional Rabi oscillations (which are of course, also present) are only weakly influenced by changes in the band structure.

Tracing Geographical Origin of Food with Application of Isotope Analysis.

Date: 2014-03-25
Speaker: Dr. Rupali Anant Lagad
Venue: Ground Floor Lecture Hall

Abstract

Dust Variability on Mars

Date: 2014-03-24
Speaker: Dr. Varun Sheel
Venue: Ground Floor Lecture Hall

Abstract

Dust aerosols are always present in the Martian atmosphere and are important in determining the thermal structure and electrical properties of the atmosphere. However, the dust cycle on Mars is not well understood, despite several years of observations of the dust opacity. In this talk, I shall present the overall status of what we know about the dust variability and the modelling efforts to understand it.

U(1)_{B-L} extra-natural inflation

Date: 2014-03-21
Speaker: Dr. Kazuyuki Furuuchi
Venue: Room No. 469

Abstract

Recently there has been an increasing support for the hypothesis that our universe once experienced an extraordinary expansion called cosmic inflation at very early time. If the inflaton, whose potential caused the inflation, does not couple to particles which can be probed by current or near future experiments, it will be challenging to uncover its microscopic identity. However inflationary models based on well-motivated particle physics theories can be constructed, with the hope that one such model was indeed realized and we can test inflation also from particle physics experiments. In this talk I will present one example of single-field slow-roll inflation model which is closely connected to particle physics beyond the Standard Model. I will also discuss general theoretical issues in inflation.

Geochemical and geological constraints on the composition of marine sediment pore fluid: Possible link to gas hydrate deposits.

Date: 2014-03-18
Speaker: Dr. Aditya Peketi
Venue: Ground Floor Lecture Hall

Abstract

Understanding Holography

Date: 2014-03-18
Speaker: Dr. Arjun Bagchi
Venue: Room No. 469

Abstract

The formulation of a quantum theory of gravity remains one of the principle challenges of theoretical physics today. The holographic principle is a unique route to address this problem. It relates a theory of gravity to a theory without gravity in one lower dimension thereby paving the way for "understanding gravity without gravity". In my talk, I present an introduction to this intriguing principle. The studies of the holographic principle has been mainly confined to Anti de Sitter spacetimes though the celebrated AdS/CFT correspondence. After mentioning this briefly, I go on to my own work which describes how one should formulate holography for the more physically relevant flat spacetimes. Our discussions would be principally based on symmetries. We will formulate flat holography as a limit of usual AdS/CFT and derive some very surprising and interesting results for 3d flat spacetimes.

Geochemical and geological constraints on the composition of marine sediment pore fluid: Possible link to gas hydrate deposits

Date: 2014-03-14
Speaker: Dr. Peketi Aditya
Venue: Room #114 (Thaltej campus)

Abstract

Geochemical and geological constraints on the composition of marine sediment pore fluid: Possible link to gas hydrate deposits

Date: 2014-03-14
Speaker: Dr. Peketi Aditya
Venue: Room #114 (Thaltej campus)

Abstract

Spin Current Driven Magnetization Dynamics and Applications in Spin Valve Pillars

Date: 2014-03-13
Speaker: C. Sanid
Venue: Room No. 469

Abstract

Spintronics is a contemporary area of technology which, in addition to the electric charge, makes use of the electron spin in designing novel, energy efficient and non-volatile memory devices and much more. In this talk the preliminary science and technology aspects needed to understand the developments in this emerging research area are introduced followed by a detailed presentation of two problems we have investigated - magneto logic gates and tunable spin torque nano oscillators.

Formation and Destruction of Polycyclic Aromatic Hydrocarbons in Interstellar Medium

Date: 2014-03-10
Speaker: Prof. K. P. Subramanian
Venue: Ground Floor Lecture Hall

Abstract

Advancements in observational, experimental, and theoretical techniques have made tremendous strides in our understanding of the role of polycyclic aromatic hydrocarbons (PAH) in the interstellar medium (ISM). In this lecture, we will examine the interstellar PAH model and its importance to astrophysics. It has been found that atomic collisions with polycyclic aromatic hydrocarbon (PAH) molecules are astrophysically particularly relevant for collision energies of less than 1 keV. The case based on analytical interaction potentials to model the interaction of low energy hydrogen and helium projectiles with isolated anthracene (C14H10) molecules will be discussed.

Dissolved Sr and its Isotope in estuaries of eastern coast of India: Impact of submarine groundwater discharge.

Date: 2014-03-04
Speaker: Mr. Damodararao Karri
Venue: Ground Floor Lecture Hall

Abstract

Status report of the laser cooled Fr EDM experiment at CYRIC

Date: 2014-02-27
Speaker: Dr. Kenichi Harada
Venue: Room No. 469

Abstract

A permanent electric dipole moment (EDM) of the elementary particles has been drawing attention as a probe for the new physics beyond the standard model (SM) in the recent decades. We are constructing Fr beam line for the electron EDM (e-EDM) measurement at Cyclotron and Radioisotope center (CYRIC), Tohoku University. Francium (Fr) being the heaviest alkali atom has a large enhancement factor of about 900 for e-EDM. Moreover, laser cooling and trapping technique dramatically elongates the interaction time with an external electric field by two or three orders of magnitude, when compared to the conventional atomic beam experiments. I shall report the current status of the development of the Fr beam line and Magneto optical trap systems for the e-EDM search.

Characterization of source, mechanism and factors responsible for isoprene emission and its role in lower atmosphere

Date: 2014-02-17
Speaker: Dr. Pallavi Saxena
Venue: Ground Floor Lecture Hall

Abstract

Isoprene is one of the most abundant biogenic volatile organic compounds (VOCs) in the atmosphere mainly produced by plants via photosynthetic activities. Emission of isoprene by terrestrial vegetation provides the dominant input of reactive non-methane hydrocarbons (NMHCs) to the atmosphere and influences tropospheric chemistry on both regional and global scales. Isoprene emission rates by plants are affected by both abiotic and biotic stresses such as temperature, light intensity, plant and leaf age, water deficit, herbivory attack, and air pollution. In India, very few studies have been reported on this issue taking biogenic volatile organic compounds (bVOCs) especially isoprene into consideration. Therefore, the highlight of this talk focuses on discussion about the sources, mechanisms and factors involved in isoprene emission and explaining some findings of isoprene concentration emitted from vegetation in a capital city of India, Delhi. I will also highlight the work to be done in PRL focusing not only on isoprene but taking other NMHCs (C2-C10), ozone and NOx into concern at cleaner and urban sites of India.

The Importance of long Histories for Flood Disaster Management.

Date: 2014-02-13
Speaker: Prof. Robert James Wasson
Venue: Ground Floor Lecture Hall.

Abstract

Long records of floods are needed to estimate return periods, document the envelope of natural variability, determine if present-day floods are outside this envelope, understand the relationship between floods and key climate drivers, and identify extreme floods as examples of what may be necessary for mitigation and adaptation. Gauged flood histories are usually short and therefore incapable of providing the data and information required. In addition, disasters are not natural but are the result of human vulnerability that is created over time. Therefore, histories of vulnerability are also needed to understand how disasters are generated. The focus of this seminar will be the construction of flood histories using geologic archives over centuries in N Thailand, the central Himalaya, and N Australia. Early results from Thailand suggest a random occurrence of large floods during the past 200 years that is likely to be the result of random occurrences of typhoons and tropical storms, and the recognition of an example of an extreme flood in the 1830’s that would have devastating consequences if it occurred today. In India and Australia large flood magnitude and frequency appear to have moved outside the envelope of variability for the past 1000 years, and frequency is non-random. Also, there are correlations between flood frequency, climate changes, and ENSO variability over the past half millennium in N Australia and India. The implications of these findings for large flood management will be explored.

Tropospheric ozone variability over different latitudes

Date: 2014-02-13
Speaker: Mr. Sandelger Dorligjav
Venue: Ground Floor Lecture Hall

Abstract

Tropospheric ozone is a greenhouse gas (particularly, ozone in the upper troposphere) that contributes to net heating and affects human health and plants (ozone in lower troposphere). In upper troposphere ozone is mostly transported from the ozone rich stratosphere (STE-Stratosphere Troposphere Exchange). Other source comes from lower layers by convection. In middle and lower troposphere, it is mostly formed by photo-oxidation of pollutants. Ozonesonde and air craft data are needed to study vertical variability of ozone. Many studies show that ozone varies from day to day and season to season as well as place to place. So, we will discuss variability of tropospheric ozone over different latitudes, the effects of meteorology on the tropospheric ozone variability (particularly in upper troposphere) and study of specific events of ozone in upper troposphere.

Probing the energetics of the multi-wavelength emission from solar flares

Date: 2014-02-13
Speaker: Dr. Arun K. Awasthi
Venue: Room # 113 (Thaltej Campus)

Abstract

Solar flares are known to be gigantic and bursty energy release events occurring in the solar atmosphere. Typically, 10^32 ergs of energy is being released in tens of minutes from a typical solar flare. Defying the standard model of energy release from solar flares, there have been innumerable instances of onset of the precursor heating prior to the commencement of the main phase emission. Although the main phase of energy release in solar flare is studied in greater detail, the underlying processes of energy release causing this precursor emission is in debate. Eventually, observations from current space missions have enabled to undertake extensive study of the precursor phase and their relationship with the whole flare energetics. I will discuss study carried out by me related to the physical processes occurring in the pre-flare plasma and their association to the main phase.

Carbon-14 and Iodine-129 as Tracers: Regional, Cosmic and Anthropogenic Effects

Date: 2014-02-11
Speaker: Dr. T. J. Jull
Venue: Ground Floor Lecture Hall

Abstract

New directions in understanding the origin of unusual structures in the MLT region using active and passive remote sensing techniques

Date: 2014-02-10
Speaker: Dr. Sumanta Sarkhel
Venue: Ground Floor Lecture Hall

Abstract

Active and passive remote sensing techniques are primarily used to investigate Earth's least explored area known as mesosphere and lower thermosphere (MLT). Na lidar is one of the active remote sensing techniques used to understand physics and chemistry in the MLT region. In addition, airglow imagers, photometers, spectrometers, meteor wind radars and incoherent scatter radars are also the key remote sensing techniques in Aeronomy. A few puzzling phenomena were recently observed in the Na layer that need to be explained in the new direction. The physical mechanism behind such unusual events from different observational sites will be discussed using various active and passive remote sensing techniques.

Photometric Study of Short Period Variables

Date: 2014-02-06
Speaker: Mr. Janaka Adassuriya
Venue: Room # 113 (Thaltej Campus)

Abstract

The detail analysis of the photometric data can be used to investigate the short period variability of the stars in the clusters and the individual variables. The present work is based on mainly 50cm CDK telescope data and its detector ANDOR CCD camera which is well capable of detecting very short period variablities in deci maginitude scale. The observations were carried out in three phases during the months of December 2013 and January 2014 at Mount Abu. Several Open Clusters and Delta Scuti type variables were observed in long time scale in different bands for the variablity study. At present the data reduction phase was initiated with some overviews of the observations. The talk is basically coveres the overviews of the observation and some techniques applied to resolve the initial problems. The Point Spred Function (PSF) and Gaussian debelending are very important tools to resolve the crowded fields as Globular Clusters. However the Globular Clusters are the most challanging part of image reduction in astronomy. Relatively Open Clusters are easy to resolve and finding variable candidates. The cluster NGC1513 was observed and instrumental magnitudes are presented. One of the interesting objects observed is SZ Lyn, a delta scuti type variable star with the period of 2.88 hours. The star is observed with a very high time resolution and the differential light curve is presented. The vigilant analyses have to be done in order to make firm conclusions.

Aspects of Quantum criticality in ferroelectrics

Date: 2014-01-31
Speaker: Dr. Nabyendu Das
Venue: Room No. 469

Abstract

Some insulating dielectric materials, namely quantum paraelectrics are found to be near a quantum phase transition. Examples include SrTiO3, KTaO3 etc. Using an effective theory, which includes transverse optic phonons near zone centre as the most relevant degrees of freedom, a self consistent approach is proposed to explain the low temperature dielectric behavior of these materials. Using finite temperature scaling near a quantum critical point, 1/T^2 behavior of the paraelectric susceptibility is predicted. The theory is extended to describe other systems where quantum paraelectric fluctuations are coupled to anti-ferromagnetic fluctuations and quenched disorder.

Perturbation series and Landau pole of effective coupling constant in quantum electrodynamics

Date: 2014-01-30
Speaker: Prof. M. Azam
Venue: Room No. 469

Abstract

Use of environmental isotopes to distinguish and estimate the sources of runoff: a case study of Kashmir Himalaya

Date: 2014-01-28
Speaker: Dr. Gh. Jeelani,
Venue: Ground Floor Lecture Hall

Abstract

Oxygen and hydrogen isotopes have been used as a tool to estimate the contributions of various components to the runoff of Liddar River in Kashmir Himalaya. Discrete seasonal variability of isotopes in precipitation and streams was found in the study area. The stable isotopes were found to be lighter at higher altitudes and in winter season. The isotopes were heavier at lower altitudes and in summer. In the present study the isotopes were also used to study the role of snow-melt and glaciers in controlling the regional hydrology.

Matter Under Extreme Conditions

Date: 2014-01-23
Speaker: Dr. Brijesh K Srivastava
Venue: Room NO. 469

Abstract

Scientists have found that everything in the Universe is made up from a small number of basic building blocks called elementary particles, governed by a few fundamental forces. Some of these particles are stable and form the normal matter, the others live for fractions of a second and then decay to the stable ones. These particles can be created only at very high temperatures and densities in the laboratory. Therefore, studying particle collisions is like "looking back in time", recreating the environment present at the origin of our Universe. The talk will focus on the Equation of State of the Quark Gluon Plasma (QGP) created in the relativistic heavy ion collisions both at RHIC and LHC energies.

Role of Atmospheric Aerosols in Climate and Human Health

Date: 2014-01-20
Speaker: Dr. Sachin S. Gunthe
Venue: Ground Floor Lecture Hall

Abstract

Aerosol particles are ubiquitous and have multiple effects on climate,and air quality. Aerosols, by absorbing and scattering incoming solar radiation play important role in Earth's radiation budget (direct effect)and by acting as cloud condensation nuclei(CCN), influence the cloud microphysical properties, their life-time, and precipitation (indirect effect)- climatic impact. To understand the effects of aerosols on climate, measurements of chemical and physical aerosol properties,mainly size distributions and concentrations, are indispensable. On the other hand the aerosol particles of biological origin, a very diverse group of biological material and structure in recent year has shown significant impact on human health and climate. The lack of proper representation of such data in climate models, due to limited measurements, is a major reason why aerosol direct and indirect effects have largest uncertainty in current understanding of climate change. The paucity of such observations over India is highly contradictory to its global relevance as major source of aerosol particles and their role in radiation budget, precipitation, and human health. It is more so important over Indian region because of high spatial variability complimented by strong season dependence due to cyclic and systematic monsoon circulations. I will present some of the measurement results from my post-doctoral stunt at Max Planck Institute for Chemistry in Mainz and current research activities of my newly established aerosol group at IIT Madras.

On the Origin of Neutrino Mass and Lepton Number Violating Searches

Date: 2014-01-20
Speaker: Dr. Manimala Mitra
Venue: Room No. 469

Abstract

Proof of neutrino masses and mixing from a series of outstanding experimental efforts have opened a window to physics beyond the standard model of particle physics. There must be some underlying theory which explains the tiny electron volt neutrino masses. It is well known that seesaw mechanism has its success in explaining the smallness of neutrino mass. In this talk I will discuss about the origin of neutrino masses and the different rich phenomenological aspects, that the underlying theories offer. The Majorana nature of the light neutrinos can be probed through the observation of lepton number violating processes. I will discuss about the different lepton number violating searches both at non-collider and collider experiments, emphasizing mostly on neutrinoless double beta decay. Apart from the well-known light neutrino contribution, lepton number violating states from a beyond standard model theory can also give large contribution in this process. I will emphasize on the sterile neutrino contribution in neutrinoless double beta decay and the interesting correlation with the lepton number violating searches at collider.

On maximizing entropy in constraining the distribution of radiogenic heat in the crust.

Date: 2014-01-17
Speaker: Dr. R. N. Singh
Venue: Ground Floor Lecture Hall

Abstract

Paleoseismology using Corals

Date: 2014-01-15
Speaker: Mr. Kaustubh Thirumalai
Venue: Ground Floor Lecture Hall

Abstract

Cometary Dust - Probe of Early Solar System

Date: 2014-01-09
Speaker: Prof. U. C. Joshi,
Venue: Room # 113 (Thaltej Campus)

Abstract

The physical and optical properties of cometary dust grains are of great interest at least for two reasons: i) these grains are responsible for much of the light scattered from cometary coma and dust tail; hence grain optics inuences the basic appearances of comets; ii) the grains are supposed to be unprocessed relics from the time of formation of the solar system or before, hence study of cometary grains is very important to investigate physical conditions that existed in the beginning of the formation of solar system. Recent space missions provide substantial and very useful information on the cometary grains. However, physical properties of the cometary dust particles may change from one comet to another. Due to limitation in the number of space missions, ground based observations are important. Solar radiation scattered by cometary dust particles is polarized and hence sensitive to the grain properties, eg, their shape, size distribution and refractive index. Polarimetric observations at dierent phase angles are therefore very useful in understanding the cometary dust properties. We have made photo-polarimetric observations on a large number of comets, e.g., Comet Halley, Hyakutake (C/1996 B2), Hale-Bopp, C/2000 WM1 (LINEAR), etc and more recently, comets 17P/Holmes and C/2007 N3 (Lulin). These observations allowed us to study cometary grains at very low (< 2 degree) to high (~110 degree) phase angles resulting in a wide coverage of negative and positive polarization branches of the polarization-phase curve. Photo-polarimetric observations on Comet Lulin were made when it was close to opposition and we detect a slow linear increase in brightness with decreasing phase angle. Also we nd polarization in negative branch of polarization to be wavelength dependent. The talk will cover a brief introduction and importance of comets and some of the recent results will be discussed.

Searching for neutral Higgs bosons in non-standard channels

Date: 2014-01-09
Speaker: Dr. Arjun Menon
Venue: Room no. 469

Abstract

In a variety of well motivated models, such as two Higgs Doublet Models (2HDMs) and supersymmetric extensions of the Standard Model (SSM), there are additional neutral Higgs bosons. The tau-tau channel is the preferred mode for discovering such scalars at the LHC. However many of these models can have a suppressed tau-tau coupling and hence alternative discovery modes are required. In this talk, I will discuss two possible modes for searching for such neutral scalars. I will discuss the prospects of observing such scalars in the 3b and H to Z A channels at the LHC and compare our projections to the present LHC limits.

Delta-18 O and Delta-D of Atmospheric Water Vapor over Bay of Bengal.

Date: 2014-01-07
Speaker: Mr. Midhun M.
Venue: Ground Floor Lecture Hall

Abstract

Multi-parameter and List Mode Data

Date: 2014-01-06
Speaker: Dr. Bhas Bapat
Venue: Ground Floor Lecture Hall

Abstract

The talk will introduce the importance of acquiring multi-parameter data, and point out what extra information can be had from obtaining correlated multi-parameter data. The second half will focus on the list-mode method of acquiring electronic data, which is naturally adapted to multi-parameter acquisition. A few instances of the use of list-mode data in collision physics and its benefits will be presented.

Causes And Patterns of Seismic Events In Gujarat.

Date: 2014-01-03
Speaker: Dr. K. S. Misra
Venue: Ground Floor Lecture Hall

Abstract

Identifying dark matter interactions in monojet searches at the LHC

Date: 2014-01-01
Speaker: Dr. Vikram Rentala
Venue: Room No. 469

Abstract

We study the discrimination of quark-initiated jets from gluon-initiated jets in monojet searches for dark matter using the technique of averaged jet energy profiles. We demonstrate our results in the context of effective field theories of dark matter interactions with quarks and gluons, but our methods apply more generally to a wide class of models. Different effective theories of dark matter and the standard model backgrounds each have a characteristic quark/gluon fraction for the leading jet. When used in conjunction with the traditional cut-and-count monojet search, the jet energy profile can be used to set stronger bounds on contact interactions of dark matter. In the event of a discovery of a monojet excess at the 14 TeV LHC, contact interactions between dark matter with quarks or with gluons can be differentiated at the 95% confidence level. For a given rate at the LHC, signal predictions at direct detection experiments for different dark matter interactions can span five orders of magnitude. The ability to identify these interactions allows us to make a tighter connection between LHC searches and direct detection experiments.

2013

Atmospheric Brown Carbon: New results from Bay of Bengal.

Date: 2013-12-31
Speaker: Prof. M. M. Sarin
Venue: Ground Floor Lecture Hall

Abstract

The relevance of chemical composition of atmospheric particulate matter is of prime concern in the present-day climate change scenario. In particular, a considerable mass of organic aerosols remains unidentified, leading to a large degree of uncertainty in assessing their impact on climate change. Recent studies have highlighted the importance of light absorbing organic aerosols, referred as brown carbon (BrC),ubiquitous and abundant over rural, urban and remote continental and marine locations. This talk will present the first field measurements of light absorbing organic aerosols (BrC) in the marine atmospheric boundary layer of the Bay of Bengal.

Why do mean-field theories fail near the critical point and how does Wilson's renormalization group method go beyond that

Date: 2013-12-31
Speaker: Navinder Singh

Abstract

Mean field theories are good qualitative descriptors of the phase transition behaviour. But all mean-field theories (including Landau's theory) fail at the critical point (the problem of large correlation length). The problems with large correlation length in quantum many-body systems are the hardest problems known in theoretical physics (both in condensed matter (like high Tc cuprates) and in particle physics (like QCD)). It was Ken Wilson's physical insights and his powerful mathematical skills that opened a way to the solution of such hard problems. With above in perspective, we will address the following questions: Why do all the mean-field theories fail near the critical point? How does Wilson's program go beyond all the mean-field theories? What are physical meanings of various kinds of fixed points? What is emergence and universality? And what is the origin of universality? (sequel of: Thermodynamical Phase transitions, the mean-field theories, and thevrenormalization (semi)group: A pedagogical introduction(*)) (*) This presentation is our tribute to Ken Wilson (the pioneer of the renormalization group) who expired few months ago.

Measurement techniques for CO2

Date: 2013-12-30
Speaker: Mr. Naveen Chandra
Venue: Ground Floor Lecture Hall

Abstract

Human activities (primarily fossil fuel use) is adding roughly 2 ppm of carbon dioxide (CO2) per year into the atmosphere. This increase in atmospheric CO2 concentration is driving global climate change via the radiative forcing effect. CO2 is the largest contributor (about 63%) to the total increase in radiative forcing by all long lived greenhouse gases. Since CO2 is a long lived gas in the atmosphere, the effect of emission on energy balance of the atmosphere is cumulative during its atmospheric lifetime. Investigating the global climate change needs extremely precise and accurate measurements of CO2 and other potential greenhouse gases. Because net change in the atmospheric CO2 levels is very small compared to its ambient concentration, these measurements must be made with extraordinary accuracy. I will be giving a summary of various techniques such as Gas Chromatography, Non Dispersive InfraRed (NDIR) and Cavity Ring Down Spectroscopy (CRDS) in this talk.

Thermodynamical Phase transitions, mean-field theories, and the renormalization (semi)group: A pedagogical introduction(*)

Date: 2013-12-26
Speaker: Dr. Navinder Singh
Venue: Room No. 469

Abstract

Lev Landau (the famous Russian physicist) made fundamental contributions in a wide spectrum of physical problems. While analysing second order thermodynamical phase transitions, he introduced a very vital concept, the concept of an "order parameter". This not only amalgamated the previous fragmentary theoretical understanding of phase transitions (an arsenal of mean-field theories) but also it put forward the important theory of "spontaneous symmetry breaking". Today, order parameter concept is a paradigm both in condensed matter physics and in high energy physics, and Landau theory is a pinnacle of all mean-field theories. Mean field theories are good qualitative descriptors of the phase transition behaviour. But all mean-field theories (including Landau's theory) fail at the critical point (the problem of large correlation length). The problems with large correlation length in quantum many-body systems are the hardest problems known in theoretical physics (both in condensed matter and in particle physics). It was Ken Wilson's physical insights and his powerful mathematical skills that opened a way to the solution of such hard problems. This presentation will be a perspective on these issues. Starting with simple examples of phase transitions (like ice/water; diamond/graphite etc) we will address the following fundamental questions: Why does non-analyticity (sharp phase transitions) arise when thermodynamical functions (i.e., free energies etc) are good analytic functions? How does Landau's program unify all the previous mean-field theories? Why do all the mean-field theories fail near the critical point? How does Wilson's program go beyond all the mean-field theories? What are physical meanings of various kinds of fixed points? What is emergence and universality? Although the presentation will deal with mundane phenomena, we will also discuss the Anderson-Higgs mechanism and the origin of mass (the Higgs boson) which is a consequence of spontaneous symmetry breaking of "the vacuum" (by comparing that with a similar phenomenon in superconductors). (*) This presentation is our tribute to Ken Wilson (the pioneer of the renormalization group) who expired few months ago.

Indian Antarctic Program - Scientific and Logistic Challenges

Date: 2013-12-23
Speaker: Mr. Rakesh P Rao
Venue: Ground Floor Lecture Hall

Abstract

Antarctica- the fifth largest continent, with average temperatures dropping to around -30 Degree Centigrade and in some places as low as -90 degree Centigrade, along with strong winds and white outs / blizzards conditions makes it one of the most hostile places for any civilization to flourish. It was realized in 1959 the importance of Antarctica for Global scientific platform for carrying out scientific research and hence came the emergence of Antarctic Treaty. In 1981 India Initiated its first Antarctic program and by 1983 the first station "Dakshin Gangotri" was established with the sole initiative to carry out scientific research in the fields of Atmospheric sciences, Meteorology, Climatology, Geology and other various branches of science. In 1989, India setup its second permanent station "Maitri" in Schirmacher Oasis, Antarctica, and now after 33 years of India's presence in Antarctica, India has setup yet another state of art research station "Bharati" with advance technology to supplement Antarctic research from new location. Indian Antarctic program- Scientific and Logistic Challenges - is a pictorial presentation that highlights my 3 consecutive expeditions as a part of the 30th, 31st and the 32nd Indian scientific expedition to Antarctica and emphasises the Indian Antarctica program and the construction of the third Indian Research Station "Bharati" in the most hostile condition on this planet. The presentation followed by a short 7 Minutes video shall take you through a journey to this bizarre yet amazing Icy continent of Antarctica.

Chemical Composition of the Solar System Ices

Date: 2013-12-20
Speaker: Ms. Aakanchha
Venue: Ground Floor Lecture Hall

Abstract

Planets and their satellites are the focus of majority of the space based missions. In general, satellites of the outer planets are called icy satellites as their surfaces are densely covered by molecular ices. However, recent findings show that there can be ices in objects that are closer to the Sun. In this talk I will be presenting the chemical composition of Solar System icy bodies and will be proposing new molecules that can be found on such icy surfaces.

Scientific photography

Date: 2013-12-19
Speaker: Rakesh Rao
Venue: Room # 113 (Thaltej Campus)

Abstract

Part1: Comet Lovejoy imaging and Landscape Astrophotography The emergence of DSLR cameras as cost effective imagining tool for Astrophotography and landscape astrophotography has revolutionised the way we look at the night sky today. The presentation would showcase the use of DSLR cameras for comet imaging and landscape astrophotography and also basic editing techniques done during the recent observation run at Mt Abu, Rajasthan and few others. Part 2: Journey to the frozen Continent ? Antarctica Situated at the bottom of the Earth, Antarctica - a Continent that expands 14 million square kilometres in area, of which 98 % is covered with snow and ice. Average temperature drop to around -30⁰ Centigrade and in places can reach to as low as 90⁰ Centigrade below zero. Now after 33 years on India?s Presence in Antarctica, India has setup yet another state of art research station ?Bharati? with advance technology to supplement Antarctic research from new location. Journey to Antarctica is a photographic presentation that highlights my 3 consecutive expeditions as a part of the 30th, 31st and the 32nd Indian scientific expedition to Antarctica and emphasises the Indian Antarctica program and the construction of the third Indian research station ?Bharati? in the most hostile condition on this planet. The presentation followed by a short 7 Mins video shall take you through a journey to this bizarre yet amazing Icy continent of Antarctica.

Decoding the geological history of the Andaman Islands.

Date: 2013-12-17
Speaker: Dr. J. S. Ray
Venue: Ground Floor Lecture Hall

Abstract

Aerosol indirect effect and dispersion bias in clouds

Date: 2013-12-16
Speaker: Dr. G. Pandithurai
Venue: Ground Floor Lecture Hall

Abstract

A major uncertainty in estimation of climate sensitivity to increased anthropogenic aerosol arises from uncertainty in estimating the aerosol indirect effect (AIE). As a consequence of increased cloud condensation nuclei (CCN) concentrations and their effect on cloud droplet dispersion, the Twomey effect (cooling) may be significantly offset over continental polluted clouds. In contrast to earlier studies on continental shallow cumuli, it is found that not only the cloud droplet number concentration but also the relative dispersion increases with the aerosol number concentration in continental cumuli. This seminar will present observational evidences on Twomey effect, effect of aerosol on droplet dispersion and estimates for dispersion bias from aircraft and ground-based measurements.

Integral Field Units : Instrumentation for Enabling 3-D Spectroscopy in Astronomy

Date: 2013-12-16
Speaker: Dr. Mudit Srivastava
Venue: Room # 113 (Thaltej Campus)

Abstract

3-D spectroscopy or Integral field spectroscopy (IFS) is a powerful tool for astronomical observations that provides spectra of individual spatial elements over a 2-dimensional area of the sky simultaneously. This in turn allows to reconstruct the image of the observed region at any given wavelength, so IFS enables to perform Hyper-Spectral Imaging of variety of extended objects. At the core of IFS instrumentation is an optical sub system called, Integral Field Unit (IFU). IFUs are the optical interface between the telescope focal plane and the conventional spectrograph, which samples the input field of view into the required spatial elements and, after suitably reformatting, feeds light from each of the spatial elements into the spectrograph that disperses and records the spectra of spatial elements individually. An IFU can be realized using different optical methods to process the incoming light e.g. using tiny lenslets, using optical fibres or using reflective mirrors. In this talk, the speaker will discuss the challenges in the design and development of fibre based method of IFU development and the corresponding IFS data characteristics.

Nera-IR study of fast nova KT Eri

Date: 2013-12-12
Speaker: Dr. Ashish Raj
Venue: Room # 006 (Thaltej Campus)

Abstract

The classical novae are close binary systems with a late-type main sequence star (the secondary) transferring material via Roche lobe overflow to a companion star (the primary). Novae brighten by 10 - 12 magnitudes in a few hours and subsequently fade back to the original faint level over a period lasting several months to years. The results obtained for nova KT Eri from the IR observations will be presented. The case B analysis of hydrogen Brackett series lines has been used to estimate the mass of the gas in the ejecta. We have found the evidence for bipolar flow, which shows the presence of two high velocity components in the nova ejecta. KT Eri is one of the very high latitude nova in last few years with galactic latitude (-32 deg) and distance below the galactic plane z ~ 3.3 kpc.

Laboratory for Low Temperature Astrochemistry

Date: 2013-12-09
Speaker: Dr. Bhalamurugan Sivaraman
Venue: Ground Floor Lecture Hall

Abstract

In this talk I will be presenting the first results that are obtained from the first of its kind dedicated laboratory for low temperature astrochemistry in India. Such a laboratory is in fact a ground based experimental support, for the efforts taken by DoS, to study chemistry on the surface of Mars and for future missions which may explore other solar system objects and beyond.

Dynamical generation of the Higgs potential and CW inflation

Date: 2013-12-09
Speaker: Professor Eung Jin
Venue: Room No. 469

Abstract

Assuming the full scalar potential vanishing at the vacuum instability scale, a successful radiative generation of the Higgs potential is achieved in the framework of a generalized B-L gauge symmetry with two free parameters, the B-L gauge coupling and the right-handed neutrino Yukawa coupling. The B-L gauge symmetry is broken spontaneously by the Coleman-Weinberg mechanism while the scale symmetry breakdown induces electroweak symmetry breaking through the radiative generation of appropriate scalar quartic couplings. Then, we revisit a small field Coleman-Weinberg inflation in this scheme. The observed amplitude of perturbations needs an extremely small quartic coupling of the inflaton which is claimed to be a signature of radiative origin. However, the spectral index obtained in a standard cosmological scenario turns out to be outside the 2 sigma region of the Planck data. When a non-standard cosmological framework which modifies the evolution of the Hubble parameter is invoked, the spectral index can be made consistent with Planck data within 1 sigma.

Study of the inner disk radius during early stages of a black hole outburst

Date: 2013-12-05
Speaker: Anjali Rao
Venue: Room # 113 (Thaltej Campus)

Abstract

Most of the black hole binaries are transient in nature. They are generally in quiescence state and enter into outburst occasionally. The behavior of the inner disk radius of the accretion disk around black holes is not very well studied during early stages of the outburst. We have attempted to study this behavior in 2010 outburst of a black hole candidate MAXI J1659-152 and found that the disk is truncated far from the black hole during its initial hard state. We noticed a systematic infall of the inner disk as the source spectrum becomes softer. In the talk, the results obtained from the study will be discussed.

Quantum Phases of Ultracold Bosonic Atoms in a One Dimensional Optical Superlattice

Date: 2013-12-05
Speaker: Prof. B. P. Das
Venue: Room No. 469

Abstract

Ultracold atoms in optical lattices have provided important insights into a wide range of physical phenomena during the past decade. My talk will begin with the landmark observation of the superfluid to Mott insulator transition in ultracold bosonic atoms in optical lattices in 2002 and then focus on the different quantum phases of ultracold bosonic atoms in a periodic one dimensional optical superlattice. The theoretical approach used in obtaining these phases will be briefly discussed. The physical situations that lead to the emergence of the Mott insulator and the superfluid phases as well as Mott insulators induced by the superlattice will be explained. Results showing the coexistence of the superfluid phase with the superlattice induced Mott insulator will be presented.

Theoretical study of electric dipole moment of ^{129}Xe atom

Date: 2013-12-03
Speaker: Yashpal Singh
Venue: Room no. 469

Abstract

Joining the seven decade long search for the existence of permanent electric dipole moment (EDM) of fundamental particles, atoms and molecules, we carry out theoretical investigation of EDM in ^{129}Xe atom. The current limits of the CP violating coupling coefficients obtained from the atomic EDMs are several orders of magnitude higher than the standard model predicted values. They, indeed, have the potential to contribute for the amount of CP violation required for explaining the matter-antimatter asymmetry of the Universe. To date the best limit for a diamagnetic atomic EDM is obtained from ^{199}Hg atom but three experiments by the leading groups around the world have considered EDM measurements in ^{129}Xe atom to surpass the present limit owing to its larger spin relaxation time. To extract the information of CP violating electron-quark coupling coefficient, EDM of a quark or other QCD parameters from the Xe EDM measurement, accurate calculations of the enhancement factors due to P- and T- violating operators and nuclear Schiff moment are necessary. In this talk, I shall briefly discuss the P- and T- violating interactions and origin of Schiff moment that are of interest for the Xe EDM study and present their high precision calculations using relativistic atomic many-body methods.

Space Science Instrumentation and my PRL Journey

Date: 2013-12-02
Speaker: Dr. Y. B. Acharya
Venue: Ground Floor Lecture Hall

Abstract

Since 1970s, instruments for Space Physics used onboard rockets, balloons and satellites have changed and improved in many aspects. We will discuss challenges involved in making space worthy instruments and also the development of space instrumentation which took place in PRL.

Aspects of type IIB large volume D3/D7 mu-Split SUSY

Date: 2013-11-29
Speaker: Dr Mansi Dhuria
Venue: Room No.469

Abstract

A phenomenological model is presented which can be obtained as a local Swiss-Cheese Calabi-Yau string-theoretic compactification with a mobile D3 and fluxed stacks of wrapped D7-branes, and provides a natural realization of mu-Split SUSY with a high SUSY-breaking scale wherein the squarks, sleptons, gauginos,Higgsino and one Higgs are very heavy and with fine tuning, one is able to obtain a 125-GeV light Higgs. We discuss the role of the (a) heavy squarks and sleptons in (ai) obtaining long-lived gluinos (a natural consequence of split SUSY), (aii) in verifying that the NLSP decays into the gravitino LSP respects the BBN constraints with the lifetime of the LSP(gravitino) coming out to be of the order or larger than the age of the universe, and (b) the light Higgs in obtaining (bi) a gravitino relic abundance of around 0.1, and (bii) electronic EDM close to the experimental upperbounds.

REE and Mo isotopic study of Permo-Triassic Sediments from Spiti, Himalaya

Date: 2013-11-29
Speaker: Dr. Vinai K Rai
Venue: Room No.#114 (Thaltej Campus)

Abstract

Invisible decays of the lightest Higgs boson in supersymmetric models

Date: 2013-11-28
Speaker: Dr. Monalisa Patra
Venue: Room no. 469

Abstract

In various supersymmetric models the lightest Higgs scalar can decay invisibly consistent with the constraints on the 126 GeV state discovered at the CERN LHC. I will briefly state the status of the invisible decays in the light of recent LHC data on SUSY and Higgs. Â Then I will mainly focus on the implications of these observations for the neutralino sector Â in the minimal supersymmetric standard model (MSSM), as well its extension containing an additional chiral singlet Â superfield, the so-called next-to-minimal or nonminimal supersymmetric standard model~(NMSSM), with both universal as well as Â nonuniversal gaugino masses at the grand unified scale.

Regionalities in geo-hydrological and hydro-meteorological processes discerned from Isotopic characteristics of Indian water sources

Date: 2013-11-26
Speaker: Dr. R. D. Deshpande
Venue: Ground Floor Lecture Hall

Abstract

It has been possible to recognize some of the characteristic isotopic(oxygen and hydrogen) patterns in various water resources of India, and their spatio-temporal variations, due to a collaborative national initiative for isotope fingerprinting (IWIN Programme). A huge volume of new isotope data from IWIN enables examining regionalities in hydrological processes and provides a unique tool to understand the ongoing geo-hydrological and hydro meteorological processes. Snap-shots of some of these processes will be presented in this talk.

Chemical composition of the Interstellar Molecular cloud

Date: 2013-11-25
Speaker: Dr. Ankan Das
Venue: Ground Floor Lecture Hall

Abstract

My research interest is to understand the physical and chemical processes responsible for producing the interstellar molecules. Hydrodynamic simulation was carried out to mimic the physical condition around the star forming region and a chemical code was developed to study the chemical evolution during these process. It was observed that interstellar dusts plays a crucial role for deciding the chemical composition of a molecular cloud. Various process involving the gas-grain interaction will be discussed. Despite of the low elemental abundances of atomic deuterium, several interstellar species are found to be heavily fractionated. In this context, deuterium enrichment of the interstellar medium and how deuterated molecular ions and deuterium fractionation could be used as a powerful tool to estimate the ionization degree of the ISM will also be discussed. One of the stumbling blocks for studying the evolution of interstellar molecules is the lack of adequate knowledge of the rate coefficients of various reactions which are taking place in the ISM. Quantum chemical calculations were carried out to study the rate coefficients of some pre-biotic molecules. Quantum chemical calculation were also carried out to obtain the vibrational, rotational and and electronic absorption spectra of several complex molecules of the ISM. It is expected that our study would throw lights on the possibility of finding some new molecules around the ISM.

X-ray and Infrared Properties of Be/X-ray Binary Pulsars

Date: 2013-11-21
Speaker: Dr. Sachindra Naik
Venue: # 113, Thaltej Campus

Abstract

Be/X-ray binaries, consisting of a compact object (neutron star) in orbit around the Be star, form the largest subclass (about 2/3) of High Mass X-ray Binaries (HMXBs). The orbit of the compact object around the Be star is wide and highly eccentric, limiting interactions with the circumstellar disk to when the objects are closest (periastron passage). Be/X-ray binaries are generally quiescent. The transient X-ray outbursts seen in these objects are thought to be due to interactions between the compact object and the circumstellar disk surrounding the Be star. The timing and broad-band X-ray spectral properties of a few Be/X-ray binary pulsars, during the regular X-ray outbursts will be discussed. Along with X-ray properties of these accreting pulsar during the outburst, the associated effect on the Be optical companion in infrared and optical bands will also be discussed.

Origin of Sediments deposited in the Andaman accretionary prism

Date: 2013-11-19
Speaker: Dr. Neeraj Awasthi
Venue: Ground Floor Lecture Hall

Abstract

Implementation of GAGAN: Challenges and Achievements

Date: 2013-11-18
Speaker: Mr. Surendra Sonda
Venue: Ground Floor Lecture Hall

Abstract

GAGAN (GPS Aided GEO Augmented Navigation) is operational in test mode since 2011 and ready for certification for aviation use. This talk would bring forth the challenges faced in implementing the GAGAN i.e. Satellite Based Augmentation System (SBAS) over Indian region. The whole program was envisioned through various stages: Technical Demonstration Stage, Final Operational Phase and Testing Phase. The working principle and in-depth architecture of GAGAN system will be covered in the talk. The various applications of the GAGAN apart from aviation use will also be discussed.

Dissolved Nd in the Ganga river system and its flux to the Bay of Bengal.

Date: 2013-11-12
Speaker: Ms. Jayatee Chatterji
Venue: Ground Floor Lecture Hall

Abstract

PAHs and Dicarboxylic Acids in ambient atmospheric aerosols from Biomass Burning Emissions in Northern India.

Date: 2013-11-05
Speaker: Dr. Prashant Rajput
Venue: Ground Floor Lecture Hall

Abstract

Organic aerosols (OA) constitute significantly (~ 20 – 90%) to the total fine particulate matter in the troposphere. They have potential to, impact aerosol composition in totality through water uptake and, interact with atmospheric trace constituents (O3, NOX and OH radical). Thus how, they have a potential role to acting as cloud condensation nuclei (CCN). Furthermore, the impact of OA on radiative forcing and atmospheric deposition of nutrients to the open ocean have been an interesting area of the atmospheric research. In this talk, two important classes of organic species: referred as polycyclic aromatic hydrocarbons (PAHs; 2–6 rings) and dicarboxylic acids (C2–C9) will be presented.

Near-infrared spectral evolution of the 2011 outburst of recurrent nova T Pyxidis

Date: 2013-10-31
Speaker: Dr. Vishal Joshi
Venue: # 113, Thaltej Campus

Abstract

Recurrent Nova is a subclass of nova showing multiple outbursts in human life time. T Pyx is one of the only 11 known nova so far.Near-infrared spectroscopic and photometric observations of the recent 2011 outburst of T Pyx will be presented. Spectra, commencing from one day after outburst, are reported for a total of 18 epochs spread over the 50 days of the eruption. A major finding is the very rare transition of the nova from the He/N to the Fe II class within a few days after the outburst. T Pyx is only second nova to show such transition after V5558 Sgr in the long history of Nova research. The evolution in the strength and shape of the line profiles is presented and discussed. A Case B recombination analysis is done which shows that the Brackett lines are a ffected by optical depth e ffects from the start to the end of the observations. Based on the observation that the Br line is clearly optically thick, we are able to place lower limits on the emission measure and electron density of ejecta.

'Rogue' Ocean Optics: The story of Peregrine Solutions

Date: 2013-10-30
Speaker: Prof. Prashanta K. Panigrahi
Venue: Room No. 469

Abstract

Rogue waves are 'walls of water' in ocean, which appear from no-where and vanishes fast, leaving no trace behind'. These has been observed in optical fibers and are being harnessed for generating super continuum, an extremely broad band source of light. They are descibed by the well-known non-linear Schrodinger equation. We will illustrate their structure and means of controlling their transient excitations.

Investigation of middle atmosphere dynamics over Brazilian and Indian stations

Date: 2013-10-28
Speaker: Dr. Amitava Guharay
Venue: Ground Floor Lecture Hall

Abstract

Waves are one of the most dominant controlling agents of dynamics of the middle atmosphere. Waves are mostly generated by disturbances due to instability, turbulence etc. in the lower atmosphere. As waves propagate through the atmosphere they transport energy and momentum from one region to the other and thus causes large scale circulation and dynamical perturbation. In my presentation I will discuss some of the important wave signatures studied from low and mid latitude stations over Brazil and India. Characteristics of the gravity waves, tides and planetary waves investigated with help of radiosonde, meteor radar observations will be elaborated.

Declining solar magnetic fields: Are we heading towards a Maunder minimum?

Date: 2013-10-25
Speaker: Prof. S. Ananthakrishnan
Venue: USO Seminar Hall

Abstract

One of the primary indicators of Solar activity is the Sunspot number and the associated 11 year solar cycle. This activity is controlled by the solar magnetic field. There are clear indications based on a variety of studies that the agnetic field on the Sun has been steadily decreasing in the past ~ 20 years resulting in lower activity on the Sun. The Sunspot formation has decreased by ~ 30% since the early 90’s. It has been speculated that if this continues, there will be no sunspots by the latter part of this decade, leading to a Maunder-like minimum in the next cycle. Using Interplanetary scintillation data from radio telescopes, surface photospheric fields measured by National Solar Observatory and He abundances measured by ACE, SDO spacecraft, my collaborators from PRL, Ahmedabad & Harvard Smithsonian Observatory and I have been studying this monotonic decrease. Interplanetary Scintillation observations between 1983 and 2009 clearly show steady drop in the turbulence levels in the entire inner heliosphere starting from around 1995. Our recent analysis of the solar magnetic fields have shown that a steady decline of the fields have taken place since around 1996 and meridional flows also appear to have changed. Similarly, Helium abundance dropped dramatically during 2008-2010. All these lead us to state that the build-up to the deepest solar minimum in 100 years actually began more than a decade earlier. We will examine the evidence in detail in this talk.

GNU Radio Beacon Receiver

Date: 2013-10-21
Speaker: Dr. Smitha Thampi
Venue: Ground Floor Lecture Hall

Abstract

The technical details of the new GNU Radio Beacon Receiver (GRBR) system for Total Electron Content (TEC) measurements using 150 and 400 MHz transmissions from Low-earth Orbiting Satellites will be presented. The GRBR system is originally designed by Yamamoto [2008] using the open-source software toolkit for the software radio, GNU Radio and the Universal Software Radio Peripheral. Using this design, we have fabricated a GRBR system, which has been installed at PRL (23.04N, 72.54E geographic) to obtain routine TEC measurements. In this talk, the details of the hardware and the software of the GRBR system and the first samples of the TEC observations will be presented.

Declining Solar Activity and the Deepest Solar Minimum in the past 100 years

Date: 2013-10-17
Speaker: Prof. P. Janardhan
Venue: # 113, Thaltej Campus

Abstract

During a roughly 11 year period, the number of sunspots seen on the solar disk shows a cyclic change. The current sunspot cycle (Cycle 24) has been strangely slow to develop and such a small solar maximum has not been observed since the Maunder Minimum from roughly 1645 to 1715. In addition the solar minimum at the end of solar cycle 23 has been one of the deepest in the past 100 years.In this talk, I will discuss the declining solar magnetic activity and look at the signatures of such a decline in the inner-heliosphere.

Recent revisions in the radiocarbon calibration database.

Date: 2013-10-15
Speaker: Dr. M. G. Yadava
Venue: Ground Floor Lecture Hall

Abstract

Perturbative expansion improved by renormalization-group summation and conformal mappings of the Borel plane for the QCD Adler function

Date: 2013-10-15
Speaker: Prof. B. Ananthanarayan
Venue: Room No. 469

Abstract

The extraction of the strong coupling constant in a reliable manner is one of the important challenges of elementary particle physics research. We will describe in detail some of our detailed theoretical investigations on this subject which employs a novel renormalization group summation scheme, which when applied to the hadronic decay of the tau produces excellent results. In this talk, we will discuss all the ingredients in a highly accessible manner, as many of the ingredients can be explained from an elementary standard point.

Ion - Matter interactions and applications

Date: 2013-10-14
Speaker: Dr. Bhas Bapat
Venue: Ground Floor Lecture Hall

Abstract

The talk will introduce basic concepts in ion - atom collisions and methods for studying the collisions. Then, focusing on the energy loss in these collisions, we will look into some applications that have emerged from the understanding of ion - atom collisions, covering diverse fields - material science, medicine and geology.

Astrophysically Interested Highly Charged Ions for Probing Temporal Variation of the Fine Structure Constant

Date: 2013-10-10
Speaker: Dillip Nandy
Venue: Room No. 469

Abstract

The possibility of temporal variation of the fine-structure constant α=e2/(ℏc) at the cosmological time scale is a subject of current interest involving particle, atomic and astro physics. Insights into this fascinating topic can be obtained from the spectral line analysis using a relativistic many-method in combination with their laboratory and/or astrophysical observations. In this seminar, I will briefly discussdifferent procedures for detecting any plausible variation of α in time and demonstrate large enhancement of this effect in the highly charged ions using a recently developed many-body method that could lead to astrophysical observation of the above subtlety in the remote past.

Environmental services: Need for more science.

Date: 2013-10-08
Speaker: Prof. R. N. Singh
Venue: Ground Floor Lecture Hall

Abstract

The Paradox of Power Loss in a Lossless Infinite Transmission Line

Date: 2013-10-03
Speaker: Dr. Ashok K. Singal
Venue: # 113, Thaltej Campus

Abstract

A famous long-standing paradox in Electrical Engineering is of a continuous power drain from the generator at the input of an otherwise lossless infinite transmission line. We show that the resolution of the paradox lies in the realization that in an open-circuit finite line, while the source does keep on supplying power as an incident wave, the reflected wave brings an equal amount back to the source,with no net power loss. The oscillations in even a simple, driven LC circuit are the superposition of incident and reflected waves. But there is no reflected wave in the infinite line, since the incident wave never reaches the termination at infinity to start a reflection. The power lost by the generator in the infinite line ultimately appears as the stored electromagnetic energy in the capacitances and inductances further down the line as the incident wave advances forward. It is also shown that contrary to some earlier suggestions in the literature, radiation plays absolutely no role in resolving this paradox.

Role of volatiles (H2O, CO2) in deep mantle.

Date: 2013-10-01
Speaker: Dr. Sujoy Ghosh
Venue: Ground Floor Lecture Hall

Abstract

Tropical convection and distribution of trace constituents in the troposphere

Date: 2013-09-30
Speaker: Dr. Lokesh Kumar Sahu
Venue: Ground Floor Lecture Hall

Abstract

Atmospheric convection is a key element of the weather and climate system for transporting mass, momentum, and thermal energy. Asian summer monsoon circulation is coupled with persistent deep convection over the South Asia region. In the tropics, deep convection plays an important role in the distribution of many trace constituents (gases and aerosols). Recent observations and model simulations have shown efficient redistribution of trace gases by deep convection. There are indications that the phenomena of El Nio and La Nia modulate the pattern of deep convection hence the distributions of trace constituents in the tropics. On the other hand, the parameterization of atmospheric convection is one of the most challenging issues in global climate modeling. Important convective parameters such as Convective Available Potential Energy (CAPE), vertical wind shear, etc. will be discussed. Some recent studies highlighting the role of deep convection in the distributions of ozone, CO and water vapor in the tropical troposphere will be presented.

Oceanic nitrogen cycling: new results based on isotopic tracers

Date: 2013-09-27
Speaker: Prof. R. Ramesh
Venue: USO Seminar Hall

Abstract

Nitrogen is abundant in the Earth’s atmosphere, but much of it is not directly useful for life. Reactive nitrogen is needed for life processes and a small amount of reactive nitrogen is controlling life processes and hence the global carbon cycle. Over the last decade, we have investigated various aspects on the marine nitrogen cycle in the Indian Ocean. Using 15N and 13C tracers we have quantified, besides the biological productivity in the ocean (rate at which carbon is fixed by photosynthesis by marine planktons, measured in units of g C m–2day–1) and its temporal and spatial variability, the ‘new production’, the fraction of the carbon that is dispatched to the deep ocean to stay for longer time scales. We have developed experimental methodologies to measure the direct fixation of atmospheric nitrogen by marine diazatrophs such as Trichodesmium in the water column and also sediments. Further we have quantified the nitrification process, which compensates for the loss of reactive nitrogen to the atmosphere by denitrification. For the latter, we have modified the traditional Rayleigh isotopic fractionation model. We have also evaluated the nitrogen transport to the ocean through rivers and atmospheric transport. In this talk, while highlighting some important new results, we also propose to discuss current and future research in this area.

Understanding Evolution of Silicate Earth using Sm-Nd systematics.

Date: 2013-09-17
Speaker: Ms. Ikshu Gautam
Venue: Ground Floor Lecture Hall

Abstract

Isotope Applications in Hydrology: Results from IWIN and Emergent Perspectives

Date: 2013-09-11
Speaker: Dr. R. D. Deshpande
Venue: Ground Floor Lecture Hall

Abstract

Land Sea interaction during last 5.5 ka around Diu Island, Western India.

Date: 2013-09-10
Speaker: Ms. Upasana Banerji
Venue: Ground Floor Lecture Hall

Abstract

The Sun and the terrestrial plasma environment: recent results

Date: 2013-09-09
Speaker: Dr. Dibyendu Chakrabarty
Venue: Ground Floor Lecture Hall

Abstract

The solar disturbances affect the terrestrial plasma environment in myriad ways and it is important to understand the processes that characterize the solar disturbances, the interplanetary medium, magnetosphere, and ionosphere so that a holistic picture can be obtained on the effects of space weather on the earth. A few results highlighting these aspects will be discussed.

Chromospheric Activity Induced Barrier in Exoplanet Detection

Date: 2013-09-05
Speaker: Mr. Vaibhav Dixit
Venue: Room # 114, Thaltej Campus

Abstract

Chromosphere is one of the three layers of stellar atmosphere. Stellar activity plays a crucial role in creating unusual temperature rise in the region. The phenomenon has been rigorously studied and modeled for sun. With the advancement of high-resolution spectroscopy, systematic chromospheric studies of various stars have been initiated on a regular basis. Sun-like periodic variations have been observed in most of the stars. In the context of exoplanet detection using radial velocity (RV) method, the chromospheric activity poses a major challenge in detecting low mass planets. With the currently available analytical models it has been predicted that chromospheric activity can induce an artificial RV variations up to 11m/s. While all the major RV survey programs are targeting to reach a meter and sub-meter accuracy, it has become extremely important to take out the activity generated effects on RV values. With the help of PARAS spectrograph we have achieved an RV precision of 1.7m/s for quiet sun like bright stars. The activity models developed from various surveys will help us to break down this barrier and avoid any false detection.

Atmospheric trace gases: transport and emission effects

Date: 2013-09-02
Speaker: Mr. Chinmay Mallik
Venue: Ground Floor Lecture Hall

Abstract

The diversity in culture and lifestyle in India is also reciprocated in anthropogenic emissions over India. Satellite observations and emission inventories clearly show that the Indo-Gangetic plain (IGP) of India is a major contributor to the national budget of anthropogenic trace gas emissions, with significant impacts from both biofuel/biomass burning as well as fossil fuel combustions. Further, trace gas and aerosol emissions need to be accurately observed and modelled, not only with respect to future emission scenarios on air quality, but also because they are the drivers of atmospheric chemistry, hence affect the Earth's radiation budget and climate. However, to model their impacts requires systematic information on their ambient concentrations and knowledge of their association with processes/factors controlling their concentrations. These factors, whose impacts vary from region to region, include emission sources (which are the cause of their input to the Earth's atmosphere), transport processes (which determine their dynamic residence time over a region) and transformation (photochemistry, loss processes including chemistry, deposition etc which determine their overall lifetime). I will be discussing the transport and emission effects on trace gas variability over a few strategic locations in and around the IGP viz. Ahmedabad, Nainital, Kolkata as well as over the Bay of Bengal (BoB). Following aspects will be discussed in detail: 1. Free tropospheric transport of SO2 over to the IGP from a volcanic eruption in Ethiopia, Africa. 2. Role of boundary layer dynamics on SO2 levels at a pristine, high altitude station to the north of central IGP from measurements at Nainital. 3. Effects of IGP emissions in its active, eastern end, at the gateway of IGP outflow into the BoB, from trace gas measurements at Kolkata megacity. 4. Fate of trace gases in transport plumes from South Asia (India, Bangladesh) and South - East Asia (South China, Vietnam, etc.) from measurements during a ship campaign.

Orbital parameters of an M dwarf arround a hot F0V star in an eclipsing binary system

Date: 2013-08-29
Speaker: Priyanka Chaturvedi
Venue: Room # 113 (Thaltej Campus)

Abstract

Eclipsing Binary systems serve as an effective tool for the precise determination of masses and radii of both the components. Despite a large number of low mass stars present in our galaxy, masses and radii for these stars are still not determined at higher accuracies, primarily due to their fainter magnitudes in visible band. Radii for stars less massive than Sun are known to be 10% smaller theoretically than observed and temperatures are 5% higher. The survey of eclipsing binary candidates from STEREO mission listed an interesting eclipsing binary candidate HD 213597, a hot F0V star, showing box like eclipses with a period of 2.42 days. We have made high resolution spectroscopy measurements on HD 213597 from the HET-HRS spectrograph at McDonald Observatory and PARAS attached to the PRL 1.2m telescope at Mount Abu. In my talk, I will be presenting the results on the orbital parameters like the determination of radial velocity semi amplitude, mass and eccentricity derived from the radial velocity data. I will also be presenting the results from the photometery measurements made on this star from the PRL 1.2 m telescope. Observations of such eclipsing binary systems will statistically contribute to the current limited samples present in the low mass regimes and help us have a better understanding of star formation and stellar evolution theories.

Extreme events and network failures

Date: 2013-08-29
Speaker: Vimal Kishore
Venue: Room No. 469

Abstract

Events like traffic jams, floods, and power blackouts are not uncommon. Inspired by such events, we study extreme events on complex networks. In this talk, we will discuss the random walk on network and associated extreme events taking place on networks. We will also propose a model to study network failures based on extreme events and discuss the nature of such failures

The Science of Geoengineering

Date: 2013-08-27
Speaker: Dr. Govindaswamy Bala
Venue: Ground Floor Lecture Hall

Abstract

Fast Vs. Slow Response in Climate Change

Date: 2013-08-26
Speaker: Dr. Govindaswamy Bala
Venue: Ground Floor Lecture Hall

Abstract

The climate system responds on multiple time scales but it has proved extremely useful to separate the responses into two distinct components: (1) a "fast response" that involves the adjustment of the atmosphere and land surface before the global mean surface temperature changes, and (2) a "slow response" that scales with the global mean surface temperature changes. Recent research shows that while the slow response is independent of the forcing agents, the fast response strongly depends on the forcing mechanisms. Specifically, the fast component shows a substantial decline in precipitation for CO2 increase while an equivalent solar forcing causes negligible fast response in precipitation. In this talk, an overview of our understanding of the global water cycle changes in a warming world will be provided. We will then discuss the mechanistic details of fast adjustment on daily time scale for CO2 and solar forcing as simulated by a global climate model. The implications to historical and future changes in water cycle and geoengineering will be also discussed.

Sounding rockets - The thrust behind atmospheric research and our capabilities

Date: 2013-08-23
Speaker: P. Ratnakar Rao
Venue: Ground Floor Lecture Hall

Abstract

Experimental Signature of cosmological neutrino condensation

Date: 2013-08-23
Speaker: Prof. M. Azam
Venue: Room No. 469

Abstract

Superfluid condensation of cosmological background neutrinos has been proposed as an alternative mechanism for generation of neutrino mess. This condensation at a low enough temperature also gives rise to a late time cosmological Constant of small magnitude. We propose that a carefully prepared beta decay experiment in laboratory can be used to find observational signature of such a condensation.

Geochemistry and Petrogenesis of Bundelkhand Granite, Central Indian Shield

Date: 2013-08-21
Speaker: Ms. Saweeta Kumari
Venue: Ground Floor Lecture Hall

Abstract

Mars Exploration and Sample Return using Dragon: A New low cost paradigm for Mars science missions

Date: 2013-08-21
Speaker: David Willson
Venue: Ground Floor Lecture Hall

Abstract

I will present details of a Mars sample return mission study done using a modified Dragon capsule that can land a Mars sample return rocket (MSR) on Mars, with a capacity to deliver a sample canister payload to either: a Lunar trailing orbit retrievable by a crewed Orion or a small robotic spacecraft and brought to Earth, or returned directly to Earth if tighter mass margins are possible. The feasibility of reducing the mission cost by adopting the emerging commercial capabilities, in particular, the SpaceX Falcon Heavy launcher that can deliver an un-manned Dragon crew capsule to Mars has been examined which will also be discussed in the seminar.

Satellite Based Navigation: an overview

Date: 2013-08-19
Speaker: Dr. Mala Bagiya
Venue: Ground Floor Lecture Hall

Abstract

The evolution of satellite based navigation started with the Transit, Timation and GPS systems. Today, Global Navigation Satellite Systems (GNSS) which refers to the satellite systems with global coverage, provide very precise positioning, velocity and timing information to every potential user. Following countries like USA, Russia, Europe and China, India has also entered into the era of satellite based navigation with two of its major projects, viz., GPS Aided Geo Augmented Navigation (GAGAN)- the Indian SBAS (space based augmentation) and the Indian Regional Navigation Satellite System (IRNSS). In my talk, I will discuss the silent features of GNSS in general and the IRNSS in particular in addition to the final operation phase of GAGAN.

Dissociation dynamics of molecules: Is there a symmetry dependence ?

Date: 2013-08-12
Speaker: Mr. Amrendra Kumar Pandey
Venue: Ground Floor Lecture Hall

Abstract

Electronic structure of a molecular system depends on the interaction between its constituent electrons and nuclei. In addition, in adiabatic picture, it is generally described in terms of the symmetry of Coulomb field created by nuclei present in the system. N2 and CO are iso-electronic systems but having different symmetries. Ionization of such molecules result in creation of molecular ions in various electronic states. The nature of the electronic state of a molecular ion decides weather it will stay as a stable system or dissociate. There are two type of processes, direct and indirect, that can be responsible for dissociation. However, occurrence of indirect processes such as auto-ionization and pre-dissociation is a signature of non-adiabatic dynamics. We observe marked differences in the kinematics of dissociation of doubly-ionized N2 and CO experimentally. Theoretical interpretation of the observed results will be discussed in this talk in terms of direct and indirect dissociation processes.

Atmospheric Processing of Ambient Aerosols: Implications

Date: 2013-08-06
Speaker: Dr. Neeraj Rastogi
Venue: Ground Floor Lecture Hall

Abstract

How Molecules form in the Star Forming Regions?

Date: 2013-08-05
Speaker: Dr. Kinsuk Acharyya
Venue: Ground Floor Lecture Hall

Abstract

Stars like our sun and planets like our Earth form in the dense interstellar medium (ISM). Dense ISM also shields interstellar radiation field and allows a rich chemistry to occur. More than 150 different gas phase molecules and around 20 molecular species on the grain surface has been detected in the various regions of ISM. Many of these molecules are organic, and therefore important astro- iologically. These molecules range in complexity from diatomic H2 to a 15-atom linear nitrile, HC13N and many of these molecules are quite unusual to find in ISM by terrestrial standards. There is a wide variety of processes that can lead to the formation of these molecules in star forming regions. These can be divided into two major classes: the reactions that can occur through the gas phase chemistry, and the reactions that occur on the surface of interstellar grains. Numerical techniques we developed to study formation of these molecules include the rate equation method, as well as several more detailed stochastic methods, based upon either the direction solution of the master equation or a Monte Carlo realization of the problem. In this talk, I will present results obtained for diffuse clouds, grain mantle compositions and its dependence on various physical parameters associated with a star forming region, effect of grain growth and grain size distribution on chemical abundances, modelling of O2 and H2O for IRAS 4A and rho Ophiuchi cloud and deuterium fractionation.

Higgs(es) in Triplet extended supersymmetric standard model at LHC

Date: 2013-08-02
Speaker: Priyotosh Bandyopadhyay
Venue: Room No. 469

Abstract

We will discuss the recent Higgs discovery results both by CMS and ATLAS at the LHC. In this context we will see the status of supersymmetric scenarios. In minimal supersymmetric scenarios to have a ~125 GeV Higgs, one needs quantum correction from strong supersymmetric sector which demands either large suspersymmetric mass scale or large mass splitting between the contributing super-particles. We focus on the triplet extension of minimal supersymmetric scenario, where we can see that the electro-weak contribution coming from triplet is also important and comparable to the strong contributions. We discussthis in the context of the observed Higgs like particle around 125 GeV and also look into the status of other Higgs bosons in the model. Along with the Higgs result we also consider flavour constraint coming from rare B decay. Finally we discuss the phenomenology of this model at the LHC.

Estimation of the low energy detection limit of a hard X-ray focal plane Compton polarimeter.

Date: 2013-08-01
Speaker: Tanmoy Chattopadhyay
Venue: Room # 113 (Thaltej Campus)

Abstract

Recently, with the advent of hard X-ray mirrors, it is now possible to build a focal plane X-ray Compton polarimeter which will be sensitive up to 80kev. However, the low energy cutoff of the operation range depends on the threshold energy in plastic scintillator used as scatterer. It has been seen that if we can lower down the threshold in plastic, sensitivity of the polarimeter increases significantly. Therefore it is necessary to accurately estimate the low energy detection limit of such plastic scintillators. In this talk, I will explain a method to measure threshold energy experimentally. I will discuss a semi-analytical model that I build up to measure the detection probability in plastic as a function of deposited energies.

Landform Evolution and Glaciers of Ladakh: Response to Climate Change

Date: 2013-07-29
Speaker: Dr. R. K. Ganjoo
Venue: Ground Floor Lecture Hall

Abstract

Mass spectrometry and optical spectroscopy of clusters

Date: 2013-07-29
Speaker: Mr. Arvind Kumar Saxena
Venue: Ground Floor Lecture Hall

Abstract

Clusters play an important role in many branches of science. Interaction between a cluster and molecules may lead to formation of a mixed cluster or a molecular cluster or a reaction may occur between the molecules adsorbed on the surface of a cluster in the presence of radiation. The first step towards studying such interactions is the development of a cluster source. We have developed cluster sources based on two techniques. The sources are diagnosed by optical emission spectroscopy and time-of-flight mass spectrometry. In this talk, I will discuss some results obtained from the diagnosis of cluster sources.

Quantum Statistics of Light from Optical Parametric Oscillator

Date: 2013-07-26
Speaker: Prof. Reeta Vyas
Venue: Room No. 469

Abstract

Optical parametric oscillators (OPOs) based on frequency down conversion are quantum mechanical sources of light with a definite threshold for self-sustained oscillations. They can be operated in degenerate or non-degenerate modes and the light generated by them exhibits nonclassical fluctuations. We obtain analytic expressions for probability distribution functions, which are valid though out the threshold region and study their fluctuations properties below, near, and above threshold. We discuss nonclassical effects in various measurable quantities such as the mean,variance, and skewness of the intensity, and quadrature squeezing, and compare with those for the single and two mode lasers

Hadronic origin TeV gamma rays and High Energy Cosmic Rays from AGN

Date: 2013-07-25
Speaker: Prof. Sarira Sahu
Venue: Room No. 469

Abstract

Centaurus A (Cen A) is the nearest radio-loud AGN and is detected from radio to very high-energy gamma rays. Its nuclear spectral energy distribution (SED) shows a double-peak feature, which is well explained by the leptonic synchrotron self-Compton model. This model however can not account for the observed high energy photons in the TeV range, which display a distinct component. Here, we show that TeV photons can be well interpreted as the neutral pion decay products from proton-gamma interactions of Fermi-accelerated high-energy protons in the jet with the seed photons around the second SED peak at 170 keV. Extrapolating the inferred proton spectrum to high energies, we find that this same model is consistent with the detection of two ultra-high-energy cosmic ray events detected by Pierre Auger Observatory from the direction of Cen A. We also estimate the GeV neutrino flux from the same process, and find that it is too faint to be detected by current high-energy neutrino detectors. In addition I shall also discuss about the flaring from Blazars using this hadronic model.

Synoptic controls of rainfall δ18O over Kerala, India

Date: 2013-07-23
Speaker: Ms. Lekshmy P. R.
Venue: Ground Floor Lecture Hall

Abstract

Investigations of MLT wave-dynamics using balloon-borne & ground-based optical, radio and magnetic diagnostics

Date: 2013-07-22
Speaker: Dr. D. Pallamraju
Venue: Ground Floor Lecture Hall

Abstract

Earth's mesosphere and lower thermosphere (MLT) region (80-120 km above the surface) is sandwiched between strong convective wave phenomena below and those of the diffusively varying & electromagnetically controlled upper atmosphere. The extremities in temperature in the MLT region and in the mode of mixing of gases gives rise to various intriguing physical processes which are important to be understood to investigate the fundamental nature of the earths atmosphere. These processes also give rise to far reaching implications in terms of redistribution of energy and momentum into the upper atmosphere. MLT region, thereby, serves as the gateway between lower/middle atmosphere and the upper atmosphere. In order to investigate the wave dynamics of the MLT region, an experiment on-board a balloon platform was conducted to obtain an assay of the waves that exist in the MLT region in the daytime. In this joint Indo-US experiment high spectral resolution optical spectrographs were flown to about 35 km altitude in the daytime from the TIFR National Balloon Facility in Hyderabad. Ultraviolet dayglow emissions were obtained that originate in the MLT region. Suite of ground-based optical, radio, and magnetic measurements complemented the balloon-based measurements. The results obtained in this expeirment will be presented. The challenges involved in carrying out such an experiment will also be discussed.

Studies of massive star forming regions

Date: 2013-07-18
Speaker: Dr. Watson P. Varricatt,
Venue: Room # 113, Thaltej Campus

Abstract

Low-mass stars are known to form through disk accretion and driving collimated outflows. When it comes to massive stars, the primary mechanism for formation has been a debated topic. The objections to an accretional scenario for the formation came from observational and theoretical considerations, and alternate scenarios like merger of lower mass stars were proposed. We have been observing massive star forming regions using the United Kingdom Infrared Telescope (UKIRT) to understand the main mechanism leading to their formation. In this talk, I will present some of the results obtained from our observations obtained using the UKIRT Wide Field Camera (WFCAM), and from archival data from ground- and space-based facilities. Studies of four interesting massive star forming regions, where multiple star formation is seen to occur in clusters, will be discussed.

Mr. A. K. Sudheer

Date: 2013-07-16
Speaker: Mr. A. K. Sudheer
Venue: Ground Floor Lecture Hall

Abstract

Timing and Spectral Properties of High Mass X-ray Binary Pulsars

Date: 2013-07-12
Speaker: Gaurava K. Jaisawal
Venue: Room # 113 (Thaltej Campus)

Abstract

High mass X-ray binaries are interesting objects to study the abrupt mass accretion from the companion star and its effect in the surrounding medium. In case of X-ray pulsars, this abrupt mass accretion changes the geometry of the accretion column near the polar caps. This change in the geometry affects the observed X-ray flux at certain pulse phases which appears as dips in the pulse profiles of the pulsars. These dips in the pulse profiles are found to be strongly energy dependent. Pulse phase resolved spectroscopy confirmed the presence of additional matter at certain pulse phases giving rise to dips in the pulse profiles. Broad-band spectroscopy of these pulsars also helps us to investigate the properties of these objects. In the seminar, I will discuss the timing and spectral studies of a few binary X-ray pulsars to understand their properties.

Magnetohydrodynamic relaxation of visco-resistive plasma

Date: 2013-07-12
Speaker: Sanjay Kumar
Venue: USO Seminar Hall

Abstract

The relaxation dynamics of a magnetized plasma system is a subject of fundamental importance in magnetohdrodyamics. The terminal states of such dynamical process are found to be rather quiescent and long lived, called as relaxed state. For example, in laboratory plasma confinement scheme like spheromak and RFP, magnetic field is believed to be in relax state. In solar corona, more than expected life time of coronal loops qualify them as relaxed states. The traits are to be looked for in a relaxing system are, predominantly non linearity and ideal integrals of motion which are conserved in absence of dissipation. In most of the existing theories of relaxation, only the terminal states are predicted without any details of the dynamics. In our study, we have tried to explore the dynamics of relaxation in a visco-resistive plasma with coronal magnetic field configuration as a prototype example using numerical simulation.

Studies of Reheating after inflation through f(φ)R gravity

Date: 2013-07-12
Speaker: Arun Kumar Pandey
Venue: Room No. 469

Abstract

Inflation is essential building block of the standard model of cosmology and has passed a number of stringent observational tests. Any inflation models must contain a mechanism by which the universe re-heats afterinflation. The reheating mechanism requires details knowledge of interactions between inflaton fields and their decay products. Since the physics behind inflation is beyond the standard model of elementary particles, the precise nature of inflaton fields is currently undetermined, and the coupling between inflaton and matter fields is often put by hand. It has found that, reheating can occure spontaneously without introducing any extra interaction between inflaton and the decay products, if inflaton is coupled nonminmally with gravity. So in this case, it is found that, inflaton field coupled with gravity nonminmally can give another channel for decay. So in this seminar, I will first discuss about reheating and then will present the reheating through a f (φ)R gravity

Analysis of the scalar potentials of "B-L" extended models

Date: 2013-07-11
Speaker: Tanmoy Mondal
Venue: Room No. 469

Abstract

The knowledge and informations related to the Standard Model (SM) Higgs mass are very crucial to understand the physics beyond it. SM-like Higgs boson, having mass in the range 123-127 GeV, squeezes the beyond standard model parameters. In recent LHC era many TeV scale neutrino mass models have earned much attention as they pose many interesting phenomenological aspects. We have considered "B-L" extended models which are theoretically well motivated and phenomenologically interesting and successfully explain neutrino mass generation. I will discuss the vacuum stability criteria for different models and how it can constrain the parameters of such models.

Relativistic heavy-ion collisions and causal viscous hydrodynamics

Date: 2013-07-10
Speaker: Manu George
Venue: Room No. 469

Abstract

Relativistic heavy ion collisions set a platform to study the properties of matter at very high temperature (T>200 MeV). The colour-deconfinement phase transition can occur at such a high temperature. This new phase of nuclear matter is called quark-gluon plasma(QGP),where quarks and gluons are no longer confined inside the hadronic volume, but move freely in a bigger volume occupied by the colliding nuclei. Relativistic hydrodynamic formalism is highly successful in describing space-time evolution of the particles produced in relativistic heavy ion collisions.One of the very important question to study in relativistic-heavy ion collision, is to accurately determine the viscosity of the strongly interacting matter. The relativistic Navier-Stokes equation is known to violates causality and gives unphysical behavior. Therefore one has to look for an alternate hydrodynamic description. One of the widely used such hydrodynamic description is due to Muller,Israel and Stewart. In this talk I will discuss about development of relativistic fluid dynamics up to second order.

Effect of SSW on low latitude dayglow emission intensities

Date: 2013-07-08
Speaker: Mr. Fazlul Islam Laskar
Venue: Ground Floor Lecture Hall

Abstract

Investigations on the wave dynamics in the daytime upper atmosphere have been initiated since 2011 after commissioning of a high spectral resolution spectrograph in a low-latitude station, Hyderabad. Atomic oxygen dayglow emission measurements from three wavelengths which emanate from different altitudes are being obtained continuously. These emissions are influenced both from the atmospheric wave forcing from below and by solar influences from above. A detailed study of the three sudden stratospheric warming (SSW) events during the years 2011, 2012, and 2013 has been carried out using ground based optical, magnetic and radio measurements which shows that the low latitude upper atmospheric dayglow emission intensities respond positively to these events. It is conjectured that the increase in the emissions after SSW commencement is due to the high- to low-latitude coupling during SSW events.

Fermi-LAT signal of monochromatic gamma ray from B-L extended SM

Date: 2013-07-08
Speaker: Tanushree Basak
Venue: Room No. 469

Abstract

The recent observation of Fermi-LAT signal of monochromatic gamma ray has drawn much attention. This observation can be due to the resonant annihilation of the dark matter into two photon. We adopt a (B_L) extended SM which contains a singlet scalar and three right-handed neutrino. The vev of the singlet scalar breaks the U(1)B−L symmetry. This scalar is heavier than the SM ones -- having mass 260 GeV. We have imposed a Z2 symmetry in such way that the 3rd generation right-handed neutrino is qualified as the dark matter candidate. The mass of this right-handed neutrino is 130 GeV. We constrain the scalar mixing angle from relic density and desired cross-section ⟨σv⟩γγ for the Fermi-line. We have also checked that this mixing angle allows vacuum stability of this model up to 105 GeV. This might hint that the successful U(1)B−L extended model that can explain Fermi-LAT signal of monochromatic gamma ray line must be a part of larger symmetry group at some high scale.

Bulk viscosity of strongly interacting matter

Date: 2013-07-05
Speaker: Guruprasad Kadam
Venue: Room No. 469

Abstract

Quantum ChromoDynamics (QCD) describes the strong interaction physics at a fundamental level. While the Lagrangian of QCD is scale invariant, quantum effects break this symmetry. This is called scale anomaly. The violation of scale invariance manifests itself in the bulk viscosity of the strongly interracting matter; so its study becomes an important as well as interesting aspect of QCD and its phases. Low temperature thermodynamics of QCD can be described by hadron resonance gas model (HRG),an effective model where the elementary degrees of freedom are hadrons. In this talk I will discuss the calculation of the bulk viscosity at finite temperature and density using Kubo's formula in the light of HRG.

Effects of anthropogenic inputs on nitrogen dynamics of a tropical estuary and adjacent coastal waters.

Date: 2013-07-02
Speaker: Ms. Bhavya P. S.
Venue: Ground Floor Lecture Hall

Abstract

ϵ′/ϵ in Standard Model

Date: 2013-07-02
Speaker: Girish Kumar
Venue: Room No. 469

Abstract

CP violation is the violation of compound symmetry associated with charge conjugation (C) and parity (P) by the weak force. It has been nearly 50 years since the surprising discovery of violation of CP symmetry in hadronic decays of kaon decays was made yet it remains as a fascinating effect because of its elusiveness at both the experimental and theoretical levels. Complex parameters ϵ and ϵ′ parametrize the indirect and direct CP violation respectively in kaon decaying to two pion. In this talk, parametrization of two pion decay will be presented. After introducing the basic formalism of operator product expansion (OPE) in weak decays , which is a formal framework to derive low energy effective theory of weak interaction of quarks, we shall discuss the theoretical status of ϵ′/ϵ in Standard Model.

Middle Atmospheric dynamics and Structure in Sub-tropical and Tropical Regions: Possible Interconnections

Date: 2013-07-01
Speaker: Dr. Som Kumar Sharma
Venue: Ground Floor Lecture Hall

Abstract

Latitudinally, the Earth's atmosphere is divided into low, mid, and high latitude regions. There is a region, bridging tropical (low-latitude) and mid-latitude, known as Sub-tropical region. The dynamical and radiative processes operative in these regions are significantly different. There are various uncertainties in the behaviour of sub-tropical regions, many questions viz., (i) Are the sub-tropical regions affected more by mid-latitude processes or low-latitude processes? (ii) How are these region coupled? (iii) What are the temporal and spatial characteristics of the middle atmospheric processes in the tropical and sub-tropical region and their interconnections?, etc. Therefore, we have utilized exiting Rayleigh Lidar observations over Mt. Abu and Gadanki and conducted coordinated campaign to study middle atmosphere in the tropical and sub-tropical region under the aegis of ISRO's CAWSES India Phase II program and tried to answer few of the above mentioned questions.

Tau Ceti and the search for Exo-earths around bright G,K dwarfs

Date: 2013-06-27
Speaker: Dr. Abhijit Chakraborty
Venue: Room # 113 (Thaltej Campus)

Abstract

Tau Ceti is only 11.9 light years away, it is the second-closest single G-type star (G9V). Its older than the Sun about 6 Gyrs, about one-third in metalicity, photometrically quiet and a radial velocity standard star. Tau Ceti is so bright and so quiet in terms of stellar jitter (seismology) that it is among the handful of stars in the sky that are best suited to long-term Doppler high-precision monitoring and defines the spectrograph stability. The star is visible in both the hemisphere and so it is in the list of all of the major Doppler surveys. In 2004 a huge cold Debris Disk with about the ten times the mass of the Kupier Belt was detected at Pluto-like distance from the star. The detection was in sub-mm wavelength using JCMT. A hypothesis was put forward that the debris disk could indicate presence of Rocky bodies from a few 100 meters size onwards and perhaps presence of inner Earth size planets. HARPS (at 1.5m/s RV precision) did a long term survey of 5 years up to 2011 and found no evidence of planet at a level of 1.5m/s precision (a few Earth Mass). Subsequently, in late 2012 a different data analysis approach on the same HARPS data was applied by another group of Astronomers and this time authors found evidence of 5 planets with one of them possibly in the habitable zone. Although this new result is highly debated in the last six months, it nevertheless opens up the necessity of further high precision continuous monitoring of the star. Finally, I will talk about PARAS efforts from Mt. Abu. From Feb 2013 we have began observing tau Ceti with PARAS and got short term precision of 1.3m/s which is very competitive with respect to HARPS. For us this serves the dual purpose of proving Spectrograph stability and as well as the Science. I will also discuss other bright G,K dwarfs with low stellar jitter like sigma Draconis (G9V). We have monitored sigma Draconis for about a year at 1.8m/s RV precision. The star has some similar characteristics with respect to tau Ceti. Although, we have not detected any earth-planet around sigma Draconis so far, it establishes PARAS capability to do so and long term stability. I will also discuss about possible planet mass upper limits on sigma Draconis. Other exo-Earths potential candidates that we have began observing recently are HD 9407 (G6V) and HD166620 (K3V).

The last tango of a vortex-antivortex pair

Date: 2013-06-27
Speaker: Kuldeep Suthar
Venue: Room No. 469

Abstract

The investigation of vortices in superfluids is a fascinating and active line of research that, by now, has a history spanning over half a century. Starting from the first observations of quantized circulation in liquid helium in the 1950s, the field has undergone tremendous progress. Nowadays, Bose-Einstein condensates (BECs) of dilute atomic gas provide a powerful tool with which vortex research can be pushed into new regimes. We theoretically investigate the effect of a repulsive barrier on the dynamics of vortex dipole. In the presence of barrier, a delicate dance ensues, and the quantum whirlpools eventually annihilate each other followed by emitting a burst of acoustic waves. In this talk, I shall discuss the effect of curvature of the vortex line on the dynamics using matched asymptotic expansion in Frenet-Serret coordinates. Finally I shall discuss the effect of transverse anisotropy of the condensate on the annihilation event.

Reconstruction of past carbon dioxide levels from Tree-ring cellulose δ13C.

Date: 2013-06-25
Speaker: Ms. Trina Bose
Venue: Ground Floor Lecture Hall

Abstract

Molecular Fragmentation:Understanding the Energetics

Date: 2013-06-24
Speaker: Mr. Koushik Saha
Venue: Ground Floor Lecture Hall

Abstract

When a molecule is excited, the excess energy is shared among the electronic and nuclear degrees of freedom. Excitation above the ionization threshold leads to the formation of excited molecular ions, which often dissociate. Since there is usually a wide gamut of energies corresponding to the opening up of various channels, an interesting question is whether there is a relationship between the pattern in which the excess energy is shared and which dissociation channels are open. Rich information about the dissociation channels and their kinematics can be gained, if the energy of the fragment ions and the electrons are monitored. In this talk, I will discuss about the fragmentation mechanisms of molecules in the light of energetics involved in the process.

Are radio morphology and optical luminosity of a radio galaxy really related?

Date: 2013-06-20
Speaker: Dr. Ashok K. Singal
Venue: Room # 113 (Thaltej Campus)

Abstract

One of the robust correlations in all observational astronomy is between the morphology type of radio galaxies and their radio luminosity. First pointed out by Fanaroff and Riley in 1974, there is a very sharp dependence of the morphology types of radio galaxies on their luminosities, so that almost all radio galaxies below a critical "break-luminosity" are edge-darkened (called FR I), while all others are edge-brightened (called FR II). This correlation has withstood the test of time. Since early 1990s there are many reports in the literature of the break-luminosity correlated with the absolute visual magnitude of the host galaxy. Based on these observational results there are many theoretical models trying to explain the dependence of radio morphology on optical luminosity, and this medelling business has grown into quite an industry. However we show that this observed correlation actually arises because of some subtle selection effects and is therefore not an intrinsic property of the radio galaxy population. It looks like all such models may have to be abandoned, unless otherwise one finds some other independent observational evidence of correlation between radio morphologies and optical luminosities.

Phase coherence in finite temperature Bose-Einstein condensates

Date: 2013-06-20
Speaker: Dr. Sandeep Gautam
Venue: Room No. 469

Abstract

We study the Bose-Einstein condensates (BECs) at non-zero temperatures using stochastic Gross-Pitaevskii equation (SGPE). This is a Langevin equation which takes the form of non-linear Schrodinger equation with additional noise and damping terms. The use of the SGPE to study both the scalar and spinor BECs at finite temperatures will be discussed in the talk. I will discuss the effect of anharmonicity on the phase coherence of quasi one-dimensional condensates.

Two-photon fields: coherence, interference and entanglement

Date: 2013-06-19
Speaker: Dr. A. K. Jha
Venue: Room No. 469

Abstract

One of the most widely used processes for generating entangled two-photon fields is parametric down-conversion. It is a second-order nonlinear optical process in which a pump photon interacts with a nonlinear crystal and breaks up into two separate photons known as the signal photon and the idler photon. The constraints of energy and momentum conservation render the two photons entangled in several different variables including time and energy, position and momentum, and angular position and orbital angular momentum. In this talk, I will present our studies of the coherence and entanglement properties of the down-converted two-photon field and will also discuss some of the practical implications of these studies for quantum information science.

When 133Cs condensate meets 87Rb condensate at finite temperature

Date: 2013-06-13
Speaker: Arko Roy
Venue: Room No. 469

Abstract

In this talk, we shall discuss the effects of finite temperature on the ground state structures of binary condensates in a highly elongated cigar-shaped trap, quasi-1D system. For this the Gross-Pitaevskii (GP) equation, valid at zero temperature, is generalized to include the effects of the interaction of the condensate with the thermal cloud, which is present at finite temperatures. For our study we use the self consistent gapless Hartree-Fock-Bogoliubov-Popov formalism, which was developed tostudy single species condensates at finite temperatures. We generalise the method to binary condensates and use it to study the ground state geometry of phase-separated profiles of binary condensates. In the strongly phase-separated domain we find doubling of Goldstone modes.

Is there a violation of the Copernican principle in radio sky?

Date: 2013-06-06
Speaker: Dr. Ashok K. Singal
Venue: Room # 113 (Thaltej Campus)

Abstract

Cosmic Microwave Background Radiation (CMBR) observations from the WMAP satellite have been reported in recent years to show some unexpected anisotropies, which surprisingly seem to be aligned with the ecliptic. This alignment has been dubbed the ``axis of evil'' with very damaging implications for the standard model of cosmology. The latest data from the Planck satellite have confirmed the presence of these anisotropies. We have found even larger anisotropies in the sky distributions of powerful extended quasars and some other sub-classes of radio galaxies in the 3CRR catalogue, one of the oldest and most intensively studies sample of strong radio sources. The anisotropies lie about a plane passing through the two equinoxes and the north celestial pole (NCP). We can rule out at a 99.995 percent confidence level the hypothesis that these asymmetries are merely due to statistical fluctuations. Two pertinent questions that arise here are - firstly why should there be such large anisotropies present in the sky distribution of some of the most distant discrete sources implying inhomogeneities in the universe at very large scales (covering a fraction of the universe)? Secondly why should such anisotropies lie about a great circle decided purely by the orientation of earth's rotation axis and/or the axis of its revolution around the sun? It looks as if these axes have a preferential placement in the larger scheme of things, implying an apparent breakdown of the Copernican principle or its more generalization, cosmological principle, upon which the standard cosmological model is based upon. Has ghost of Aristotel struck with vengeance?

Explaining Fermi-line and enhanced Higgs di-photon rate in the Triplet-Singlet extended MSSM

Date: 2013-06-06
Speaker: Tanushree Basak
Venue: Room No. 469

Abstract

We propose an economic extension of minimal supersymmetric standard model with a SU(2) singlet and Y = 0 triplet, which can explain (i) the 125 GeV Higgs boson without fine tuning, (ii) the 130 GeV gamma-ray line seen at Fermi-LAT, (as well as a second photon line at 114 GeV)(iii) an enhanced Higgs di-photon decay rate seen by ATLAS, while being consistent with dark matter relic density and recent XENON 100 exclusion limits on spin-independent direct detection cross-section. We obtain the required cross-section of 10−27cm3s−1 for the 130 GeV gamma-ray flux through the resonant annihilation of dark matter via pseudoscalar triplet Higgs of mass ~260 GeV. The dark matter is predominantly bino-higgsino which has large couplings with photons (through higgsino) and gives correct relic ensity (through bino). We get the enhanced Higgs diphoton decay rate, R ~ 1.224, dominantly contributed by the light chargino-loops, which can account for the reported excess seen in the h to gamma gamma channel by ATLAS.

Understanding the long timescale variability in blazars, a case of FSRQ PKS 1510-089

Date: 2013-05-23
Speaker: Sunil Chandra
Venue: Room # 113 (Thaltej Campus)

Abstract

BL Lacs and Flat Spectrum Radio Quasars (FSRQs) are collectively known as Blazars. It is well established fact blazars are a subclass of Active Galactic Nuclei (AGNs) seen at very small angles (<=15 deg) to the jet of relativistic plasma emanating perpendicular to the plane of accretion disk. Blazars emit non-thermal continuum emission over the entire energy spectrum i.e ranging from radio to VHE Gamma-Rays through Optical/X-ray. The main differences between BL Lacs and FSRQ are, to first order, that the FSRQ are more distant, more luminous, and have stronger emission lines. This era can be assumed to be the golden time for studying such objects. A rich sample of blazars are regularly monitored by VLBI radio and several optical facilities all over the globe. Swift/AGILE/SUZAKU/MAXI and Fermi are providing good amount of data at high energies. HESS/MAGIC and several others are exploring Extreme Energy Gamma-Rays (TeV) which completely untouched part of spectrum . In short we have opportunities to get the complete coverage of blazar SED almost simultaneously. There are several studies by many authors about disk and jet connections in blazars. Though the formation and collimation of jets in AGN are not well understood, one can estimate some of the key properties of the system based on present observations. In the present study we are investigating FSRQ PKS 1510-089 for variability of all possible time scales in different energy bands. The purpose of this seminar is to review the current understanding these systems and here we are using PKS 1510-089 as an example.

A novel scheme for qudit teleportation

Date: 2013-05-23
Speaker: Chithrabhanu P
Venue: Room No. 469

Abstract

Quantum teleportation is the process in which, the quantum state of a particle is transferred to another without direct interaction. Efficient quantum teleportation of multi dimensional quantum bit (qudit) is one of the prime requirement in quantum circuits. We investigate the possibility of a new entanglemed state for 100% qudit teleportation. In the talk I will discuss the basic teleportation protocol, its experimental realization, hyper entanglement , possibility of a new entangled state and its use in qudit teleportation.

From urban centers to the remote atmosphere: airborne observations of black carbon aerosol

Date: 2013-05-20
Speaker: Dr. Anne E. Perring
Venue: Ground Floor Lecture Hall

Abstract

Black carbon (BC) aerosol is a product of incomplete combustion that has far-reaching impacts in the global atmosphere. It is the second strongest positive anthropogenic radiative forcing after CO2 affecting climate both through its direct absorption of radiation and through its impacts on cloud and snow albedo. The net forcing from global BC emission sources, however, remains highly uncertain. Some of the largest uncertainties in global BC lifetime and distribution arise from uncertainty in the timescale on which BC acquires coatings and, relatedly, on BC?s affinity for water. Our research group at NOAA has undertaken numerous airborne field deployments in recent years to investigate emission, transformation and transport of BC in a wide variety of environments from urban centers to the remote atmosphere using a Single Particle Soot Photometer (SP2). In this talk, I will introduce the SP2 technique for detecting BC aerosol with a focus on the instrument?s ability to determine BC coating state. I will also discuss the newly developed Humidified Dual SP2 (HD-SP2) which allows us to directly probe BC?s affinity for water. I will then present salient results from recent measurement campaigns from urban to remote environments tracking BC microphysical properties (particle size and coating state) and their implications for BC aerosol transport, processing and loss.

X-ray binary evolution and their collective properties

Date: 2013-05-16
Speaker: Dr. Harshal Bhadkamkar
Venue: Room # 113 (Thaltej Campus)

Abstract

X-ray binaries are the binary systems of a normal star and a compact object. Compact object accretes material from the normal star and the accretion energy is observed as X-ray emission from these sources. X-ray binaries are considered as one of the dominant X-ray sources in galaxies and their collective emission is thought to be a major part of the total X-ray luminosity of galaxies. I will first briefly discuss the life-history of these objects. I will then go on to show how are the evolutionary mechanisms used to derive the collective properties of these objects. Theoretical results derived will be compared with the observations. I will then turn to the subject of tidal evolution in these objects. I will discuss the effects of tidal synchronization on the orbit and subsequently on the evolutionary path. Finally I will present future outlook, looking ahead of the simplified evolutionary picture.

Annihilation of vortex dipoles in Bose-Einstein Condensate

Date: 2013-05-16
Speaker: Shashi Prabhakar
Venue: Room No. 469

Abstract

One of the recent developments in experiments on atomic Bose-Einstein Condensate (BEC) is the creation of vortices and study of their dynamics. We have theoretically explored the annihilation of vortex dipoles, generated by the movement of obstacle through an oblate BEC. We have also examined the energetics of the annihilation events. We have observed that the gray soliton, which results from the vortex dipole annihilation, is lower in energy than the vortex dipole. We have also observed the annihilation events numerically and found that the annihilation occurs only when the vortex dipole overtakes the obstacle and comes closer than the coherence length. Furthermore, we have found that the noise reduces the probability of annihilation events. This may explain the lack of annihilation events in experimental realizations. In this talk, we will discuss about observations obtained from the study on annihilation of vortex dipoles in BEC

Fast solar polarimeter: Concept and the lab measurements

Date: 2013-05-15
Speaker: Dr K. Nagaraju
Venue: USO Seminar Hall

Abstract

A new polarimeter is under development at the MPS towards a goal of carrying out high precision spectropolarimetric observations on the Sun, combined with increased high spatial resolution. The polarimeter is based on pnCCD detector technology from PNSensor. The CCD detector can be operated at frame rates of up to 1000 frames/s to suppress spurious polarization signals induced by the atmospheric turbulence or instrument jitter. The polarization modulator is based on two ferro-electric liquid crystals and two static retarders. Achromatism in terms of polarimetric efficiency is achieved through appropriate positioning of the retarders. In this talk I will discuss about working principle and laboratory test results of the new polarimeter.

Coherent pump-probe spectroscopy of atomic and molecular systems

Date: 2013-04-29
Speaker: Ms. Niharika Singh
Venue: Room No. 469

Abstract

Quantum coherence and interference provide an interesting outlook for designing strategies for the control of optical response of atomic/molecular medium. This theme is the main focus of the work presented in this talk. The specific issues addressed are electromagnetically induced transparency (EIT), amplification without inversion (AWI) and spontaneously generated coherence (SGC). Also examined are the issues related to the effect of permanent dipole moments on the coherent dynamics of molecular systems and realization of negative refractive index in coherently prepared atomic medium. These phenomena help to understand the subtle quantum effects in laser-atom interactions, they on the other hand provide useful platform for development of quantum technologies.

Narrow band imager for Multi Application Solar Telescope at Udaipur Solar Observatory

Date: 2013-04-26
Speaker: A Raja Bayanna
Venue: USO Seminar Hall

Abstract

Multi-Application Solar Telescope (MAST) is an off-axis Gregorian solar telescope of 50 cm clear aperture being installed at the lake site of Udaipur Solar Observatory (USO). A narrow band imager is being developed for near simultaneous observations of the solar atmosphere at different heights. The heart of the system is two LiNbO3 Fabry-Perot (FP) etalons working in tandem. It is important to calibrate the system for a change in voltage and a change in temperature for near simultaneous observations in different wavelengths. A Littrow spectrograph was set up to calibrate the FP etalons using a 15 cm refractor as a light feed. Calibration is carried out for the solar spectral lines at Fe I 6173 Å, and Ca K 8542 Å. In this presentation we discuss the temperature and voltage tuning of the system. We also present the details of the calibration set-up and obtained parameters along with the first-light results of the system.

A study on sudden impulses in the geo-magnetic fields

Date: 2013-04-25
Speaker: Susanta Kumar Bisoi
Venue: Room # 113 (Thaltej Campus)

Abstract

Solar initiated interplanetary disturbances, the direct consequences of explosive events on the Sun such as Coronal Mass Ejections (CMEs) and solar flares, drive space weather events and are the obvious sources for geo-magnetic events on the earth. In this talk, I will begin with a discussion on the coupling of the solar wind plasma with the earths magnetosphere and their subsequent role in development of different magnetospheric and ionospheric processes that prompt or trigger the buildup of geo-magnetic events. In addition, our recent work on the study of sudden impulses in the geomagnetic fields will be discussed.

Characterization of LCVRs for MAST polarimeter

Date: 2013-04-25
Speaker: Alok Ranjan Tiwary
Venue: USO Seminar Hall

Abstract

Spectro-polarimetry analyzes light as a function of its two most important characteristics: wavelength and state of polarization and is a powerful tool for measuring the magnetic field on the Sun. The observational aim of solar spectro-polarimetry is to record the Stokes vector as accurately as possible with highest spectral, spatial and temporal resolution. A Polarimeter is being developed at USO for measuring the vector magnetic field in the solar atmosphere at two different heights, and it will be used with the newly installed MAST. We plan to use two LCVRs and a linear polarizer for the MAST Polarimeter. LCVRs are electro-optically tunable retarders. Characterization of each LCVR is important in order to get the accurate retardance and voltage dependence for a particular wavelength. In this presentation, we discuss about the calibration of the LCVRs for two solar spectral lines at Fe I 6173 Å, and Ca K 8542 Å. We also present the details of the calibration set-up and the obtained results.

Spectroscopic Properties of atoms/ions in the presence of screened inter-electron interaction.

Date: 2013-04-25
Speaker: Dr. Madhulita Das
Venue: Room No. 469

Abstract

We have theoretically studied the atomic structure and properties of multi-electron system in both weak and strong plasma environment using Debye and Ion-Sphere model, respectively. The Many-body method adapted for the computation is the Relativistic Coupled Cluster method to include eﬀectively the relativistic and correlation effects in the calculations using Gaussian type orbital (GTO). In addition to nuclear screening effect, the plasma screening effect have been extended to electron-electron Coulomb interaction between the atomic electron of highly charged atomic/ionic systems embedded in plasma. The main focus is to analyze the inﬂuence of inter-electron screening effect on the spectroscopic properties of highly charged Lithium iso-electronic sequence with increasing plasma strength.

Ambient mass spectrometry for systematic study of chemicals and pesticides in vegetables and herbs

Date: 2013-04-23
Speaker: Dr. Amzad Hussain Laskar
Venue: Ground Floor Lecture Hall

Abstract

E-region plasma waves over Thumba: Recent progress

Date: 2013-04-22
Speaker: Prof. R. Sekar
Venue: Ground Floor Lecture Hall

Abstract

Two types of plasma waves namely streaming plasma waves and gradient drift plasma waves are excited in the E-region of the ionosphere over dip equator location. These plasma waves over Thumba, India, a location closer to the dip equator, have been investigated over the years by rocket borne in situ probes and ground based radars. Recently, two RH-300 MkII rockets containing Langmuir probes were flown from Thumba on 15 and 16 January 2010 to investigate equatorial E-region of the ionosphere. The results obtained from this rocket flight campaign are compared with the previous results obtained from the same location using various techniques. The importance of the scientific results will be highlighted in this talk.

Vacuum polarization correction in many electron atoms with triples excitation in relativistic coupled-cluster theory

Date: 2013-04-18
Speaker: Siddhartha Chattopadhyay
Venue: Room No. 469

Abstract

In this talk We shall discuss about the importance of the vacuum polarization correction in the calculation of orbital energies in many electron atoms. The Uehling potential is the leading order term in the vacuum polarization. We incorporated the Uehling potential in the Dirac-Hartree-Fock self consistent field calculation of many electron atoms. We shall discuss how it affects the orbital energies and why it is important for highly charged ions. We will discuss some preliminary results of highly charged Barium ions. In the next part we will discuss about the triples excitation in the relativistic coupled-cluster (RCC) theory. Most of the RCC calculations are done with the singles and doubles excitations. Because of complicated angular momentum diagram and enormous computational cost there are very few calculations have been performed with the actual triples excitation. We will discuss the necessity of triples excitation in present era of high precision calculation. We will present some preliminary results of Lithium in the framework of RCCSDT theory.

Early Differentiation of the Silicate Earth

Date: 2013-04-09
Speaker: Ms. Ikshu Gautam
Venue: Ground Floor Lecture Hall

Abstract

Noise reduction in lunar occultation light curves using Wavelet and Fourier transforms.

Date: 2013-04-04
Speaker: Dr. Tapas Baug
Venue: Room # 114 (Thaltej Campus)

Abstract

Lunar Occultation (LO) is a powerful ground based technique to measure the angular diameter of stars even with a moderate size 1 m class telescope. A good signal to noise ratio (S/N ~ 40) of the observed light curve is prime requirement to extract proper angular diameter information of the source. However, an LO light curve with better S/N can also help to measure the circumstellar contribution of a star, in addition to its stellar angular diameter. With present set of instruments 2-magnitude fainter objects are being observed. Hence, methods to improve S/N of the observed light curve using Wavelet Transforms and Fourier Transforms have been studied. In previous talk, the aspect of S/N improvement was discussed. Further analysis has been carried out for S/N enhancement of the light curves, as well as, to examine the improvement in their model fits. Particulars will be presented.

Status of two popular models of supersymmetry with and without seesaw

Date: 2013-04-04
Speaker: Dr. Ketan Patel
Venue: Room No. 469

Abstract

The results of updated analysis will be presented for two highly-constrained models of supersymmetry -- the constrained minimal supersymmetric standard model (cMSSM) and the non-universal Higgs mass model (NUHM) -- in the light of the recent discovery of Higgs boson and updated results on the several flavour physics observables. It turns out that these models can still survive and predict a light stop with mass < 1.5 TeV. I will also report on the status of the extended versions of cMSSM and NUHM models which accommodate seesaw mechanisms. The recent measurement of the reactor angle and new MEG limit on μ → e γ provide powerful constraints on these class of models. The potential of the current and future experimental searches in constraining the supersymmetric parameter space will also be discussed.

Subsurface imaging - challenges and opportunities

Date: 2013-04-02
Speaker: Prof. Mrinal Sen
Venue: Ground Floor Lecture Hall

Abstract

Free Space Optics - Technology Overview

Date: 2013-04-01
Speaker: Dr. Y. B. Acharya
Venue: Ground Floor Lecture Hall

Abstract

Free Space Optical communications (FSO) has attracted considerable attention for a variety of applications in telecommunications field. In free space optical communication, data is transmitted from point-to-point and multipoint using low-powered infrared lasers. FSO allows transmitting and receiving of voice, video, and data information. High speed and license free installation are the key features of this technology. The performance of FSO link is significantly affected by meteorological conditions viz. rain, scintillation, geometric attenuation and snow etc. Various issues and challenges associated with it will be discussed.

Higgs-to-diphoton in type II seesaw

Date: 2013-03-28
Speaker: Dr. Pankaj Sharma
Venue: Room No. 469

Abstract

I will talk about Higgs-to-diphoton rate in type II seesaw model. We also discuss the constraints on the model parameter space coming from vacuum stability, perturbativity and electroweak precision tests. In the constrained parameter space, we study the modified Higgs-to-diphoton rate.

Response of low-latitude ionosphere to the disturbed geomagnetic conditions

Date: 2013-03-25
Speaker: Dr. Sneha Yadav
Venue: Ground Floor Lecture Hall

Abstract

The disturbed geomagnetic conditions have significant influence on the dynamics of the low latitude ionosphere-thermosphere system which is the matter of intense research across the globe. The disturbed geomagnetic conditions are capable of generating large scale perturbations in neutral composition, electric fields and the global circulation of the thermosphere which in turn perturb the ionosphere significantly with respect to its quiet time state. In this context, some observations based on ionosonde and satellite borne plasma measurements on the response of low-latitude ionosphere to the disturbed geomagnetic conditions will be presented and discussed.

Mass measurement techniques for BSM particles in collider experiments

Date: 2013-03-22
Speaker: Abhay Kumar Swain
Venue: Room No. 469

Abstract

Most of the theories beyond the Standard Model(BSM) includes unstable heavy particles which can decay into a stable invisible particle. If LHC observes any BSM particles we must be able to determine their masses and other properties. In this talk I will discuss some of the mass measurement techniques which tell how to measure the masses of both stable as well as unstable particles in collider experiments.

A tyro's foray into mathematics -- my solutions of the cubic equation

Date: 2013-03-21
Speaker: Prof. D.P.K. Banerjee
Venue: Room # 114 (Thaltej Campus)

Abstract

The history of algebraic equations has oodles of high voltage drama in it. The cubic equation was first solved by a stammering Tartaglia, a man who had his face slashed by a sword. It also involves a thieving mathematician (Cardano) who stole those first results and passed them off as his own. The fifth order equation, the quintic, is inseparably linked with the tragic genius of Evariste Galois killed in a duel at the impossibly young age of 20 ; much younger in death than Byron or Shelley or Keats. My foray into this world was to understand why the standard method of solving the cubic equation always worked with the "reduced" form of the equation. Was there not a way in which one used the entire equation? In this talk I will answer this question, offer new solutions and also present an unified method to solve algebraic equations. I will also explain how solving crosswords proved to me that the human brain could work in its sleep and validated the inscrutable advice by one of PRL's most distinguished scientists to a young researcher "Don't waste time in the day in thinking, that can be done at night when you sleep".

Dr. Aditya Peketi

Date: 2013-03-19
Speaker: Dr. Aditya Peketi
Venue: Ground Floor Lecture Hall

Abstract

Synthesis on the E-region plasma instabilities based on long-term rocket measurements from Thumba

Date: 2013-03-18
Speaker: Prof. S. P. Gupta
Venue: Ground Floor Lecture Hall

Abstract

Rocket-borne Langumuir probe measurements of E-region plasma instabilities were carried out from Thumba for several decades. These results will be discussed and compared with the global empirical vertical plasma drift field model (Scherliess and Fejer, 1999).

Centenary of Bohr's Atom Model and its relevance to contemporary science

Date: 2013-03-14
Speaker: Prof. M. D. Sastry
Venue: Room No. 469

Abstract

-NA-

High resolution Paleoclimatic Reconstruction and Speleothem dating

Date: 2013-03-12
Speaker: Ms.Shraddha Band
Venue: Ground Floor Lecture Hall

Abstract

On the recent problem encountered by the GSV dual frequency GPS receivers

Date: 2013-03-11
Speaker: Dr. Mala Bagiya
Venue: Ground Floor Lecture Hall

Abstract

Dual frequency GPS receivers are used to derive the total electron content(TEC) along the line-of-sight of the satellite and the receiver. The position and time information recorded by these receivers are extremely important for the interpretation of the TEC data. GPS receivers provide the position and time information based on the range and ephemeris information of any four GPS sate

Quark and Gluon Angular Momenta Contributions to Nucleon Spin (χQCD Collaboration)

Date: 2013-03-07
Speaker: Dr. Mridupawan Deka
Venue: Room No. 469

Abstract

The nucleon spin structure has been a longstanding issue in hadronic physics,both experimentally and theoretically. From the polarized Deep Inelastic Scattering experiments and Lattice QCD calculations, it has been found that the contribution coming from the quark spin is rather small (~25%). Now, it is widely accepted that the rest of the nucleon spin should come from the gluon spin and the orbital angular momenta of quarks and gluons. In this talk, I will present a complete Lattice QCD calculation of the quark and glue angular momenta inside a proton. The calculation is carried out on a 16^3×24 quenched lattice using the standard Wilson action.

Harmful Algal Blooms in the Arabian Sea

Date: 2013-03-05
Speaker: Dr. Arvind Singh
Venue: Ground Floor Lecture Hall

Abstract

Global geomagnetic response to solar wind - magnetosphere coupling

Date: 2013-02-25
Speaker: Anand K. Singh
Venue: Ground Floor Lecture Hall

Abstract

Freshly injected energetic charged particles from the magnetotail reach to high latitude ionosphere along the field lines and also enter across the field lines in the equatorial plane. Large flux of energetic plasma reaching to high latitudes intensify auroral electrojets and subsequently generate geomagnetic substorms, whereas radially trapped plasma drift in longitudes and enhance the ring current. Geomagnetic field observations have been regularly used to monitor these currents remotely. This presentation aims to discuss the ground-based detection of drifting energetic ions and electrons in the ring current region. In addition, high and low latitude coupling during substorm and their various manifestations will be discussed in detail.

Neutino mass Hierarchy and Octant determination with T2K and NoVA

Date: 2013-02-22
Speaker: Professor S. Umashankar
Venue: Room No. 469

Abstract

I will discuss the resolution of two outstanding issues in neutrino physics -- mass hierarchy and octant of the 2-3 mixing angle in the upcoming long baseline experiments T2K and NOVA.

Spectral statistics of interacting trapped bosons

Date: 2013-02-21
Speaker: Prof. Barnali Chakrabarty
Venue: Room No. 469

Abstract

It is very much interesting to study the energy-level statistics of interacting trapped bosons which are spatially inhomogeneous. We study the zero-temperature many-bosons system interacting through thevan der Waals potential and confined in a 3D harmonic potential. The system is a kind of complex system where the two energy scales co-exist. One is the external trap and another is the interatomic interaction. In case of repulsive interaction the lower levels are correlated manifesting level-repulsion. For non-interacting bosons exact degeneracy exists and the energy-level statistics shows picket-fence type nature. But for a few bosonic system the small interaction acts like perturbation and consequently a large number of quasi-degenerate states occur showing Shnirelman peak in P(s) distribution. For large number of bosons the low-lying levels are of collective nature and strongly affected by the interatomic interaction whereas the high-lying levels show single particle excitations. The corresponding level fluctuation shows a transition from close to Wigner to Poisson with increase in energy levels implying that it does not obey the Bohigas universal conjecture. Thus interacting trapped bosons may be a generic example to show that 1/fα noise is ubiquitous in nature and α not only measures the chaoticity of the system but also measures the degree of integrability for complex systems.

Did Sarasvati flow into the Great Rann of Kutch 5000 years ago?

Date: 2013-02-19
Speaker: Mr. Anirban Chatterjee
Venue: Ground Floor Lecture Hall

Abstract

Determination of Mueller matrix of an optical element with Simon-Mukunda polarization gadget

Date: 2013-02-18
Speaker: Salla Gangi Reddy
Venue: USO Seminar Hall

Abstract

To characterize the polarization changes due to any optical element, one needs to determine the Mueller matrix of that element. From the information obtained by Mueller matrix, one can know the performance of an optical system and how to compensate those changes by using wave plates. In this talk, I will discuss a novel method to determine the Mueller matrix and the error associated with it due to the optical system used for its determination.

Langmuir Probe design for RH 200

Date: 2013-02-18
Speaker: Prof. R. N. Misra
Venue: Ground Floor Lecture Hall

Abstract

RH 200 is a small sounding rocket which can be utilized for studies of plasma parameters up to about 130 Km, the region served so far by a larger RH 300 rocket. Langmuir probe sensor, suitable for RH 200 rocket nose cone and signal processing electronics accommodated on a single printed circuit board (PCB), have been developed. The PCB can be easily mounted in the payload section of RH 200.

Blazar sequence and polarization

Date: 2013-02-14
Speaker: Prof. K. S. Baliyan
Venue: Room # 114 (Thaltej Campus)

Abstract

Blazars are powerful AGNs with emission dominated by the relativistic jet. Their continuum spectral energy distribution is characterized by two humps, peaking at low and high energies. Based on the position of lower peak (called synchrotron peak) and other properties, blazars are classified into a sequence, called blazar sequence; FSRQ, LBL, HBL. Their luminosity decreases from FSRQ to HBL and so does the gamma-ray emission dominance. These properties help in the study of a blazar candidate. It is also noticed that generally FSRQs have higher degree of polarization as compared to HBLs and we show that polarization can be used to classify blazars. For this, polarization and spectral energy distribution of a blazar candidate will be discussed.

Report on visit to NCU, Taiwan to attend ISWWS-2013

Date: 2013-02-11
Speaker: Wageesh Mishra
Venue: USO Seminar Hall

Abstract

In this talk, I will present a very brief overview of scientific lectures delivered by various experts in International Space Weather Winter School, held during 21- 26th January 2013. I will discuss about various hands-on projects allotted to participants of winter school. Mainly, I will discuss the theory of Interplanetary scintillation and its importance to understand the density fluctuations in the heliosphere. I will also show few results on evolution of Coronal Mass Ejections in the interplanetary medium obtained by implementing IPS technique, various MHD models and using Solar Mass Ejection Imager (SMEI) observations.

Computational hydrodynamics for complex systems

Date: 2013-02-11
Speaker: V. L. Patel
Venue: Ground Floor Lecture Hall

Abstract

Advances in computation science, numerical methods and availability of supercomputers make possible study of large-scale complex nonlinear phenomena. Problems in atmospheric and oceanic sciences, astrophysics, galactic dynamics, inertial confinement fusion etc are being studied by numerical simulation. Selected examples such as Arizona sand storms (haboob),hurricanes, tsunami, giant rogue ocean waves, ICF, galactic collisions will be discussed.

Lepton masses and Flavour violation in Randall Sundrum Model

Date: 2013-02-07
Speaker: Abhisek Iyer
Venue: Room No. 469

Abstract

Lepton masses and mixing angles via localization of 5D fields in the bulkare revisited in the context of Randall-Sundrum models. The Higgs is assumed to be localized on the IR brane. Three cases for neutrino masses are considered: (a) The higher dimensional LH.LH operator (b) Dirac masses (c) Type I see-saw with bulk Majorana mass terms. Neutrino masses and mixing as well as charged lepton masses are fit in the first two cases using chi-square minimisation for the bulk mass parameters, while varying the O(1) Yukawa couplings between 0.1 and 4. Lepton flavour violation is studied for all the three cases. It is shown that large negative bulk mass parameters are required for the right handed fields to fit the data in the LH LH case. This case is characterized by a very large Kaluza-Klein (KK) spectrum and relatively weak flavour violating constraints at leading order. The zero modes for the charged singlets are composite in this case and their corresponding effective 4-D Yukawacouplings to the KK modes could be large. For the Dirac case, good fitscan be obtained for the bulk mass parameters, ci, lying between 0 and 1. However, most of the `best fit regions' are ruled out from flavour violating constraints. In the bulk Majorana terms case, we have solved the profile equations numerically. We give example points for inverted hierarchy and normal hierarchy of neutrino masses. Lepton flavor violating rates are large for these points. We then discuss various minimal flavor violation (MFV) schemes for Dirac and bulk Majorana cases. In the Dirac case with MFV hypothesis, it is possible to simultaneously fit leptonic masses and mixing angles and alleviate lepton flavor violating constraints for Kaluza-Klein modes with masses of around 3 TeV. Similar examples are also provided in the Majorana case.

Study of Sources in very High Energy Regime Using Ground Based Gamma-ray and Neutrino Telescopes

Date: 2013-02-06
Speaker: Dr. Debanjan Bose
Venue: Room No. 469

Abstract

In this presentation I will talk about sources like pulsars, AGN and GRBs in very high energy regime. At these energies we study non-themal Universe. From observations we know that relativistic effects are taking place inside these objects. These sources emit high energy gamma-rays and are also expected to emit neutrinos. I will explain detection principle of gamma-rays and neutrinoswith earth based detectors. I will also discuss some important observations for the above mentioned sources with ground based Cherenkov telescopes and IceCube neutrino observatory. Finally, I will briefly talk about neutrino point source analysis following Bayesian statistics.

Hunting for Blackholes with LIGO- India

Date: 2013-02-05
Speaker: Prof. Fred Raab Head
Venue: USO Seminar Hall

Abstract

Theoretical study of the solar magnetic cycle and its irregularities

Date: 2013-02-04
Speaker: Dr. Bidya Binay Karak
Venue: USO Seminar Hall

Abstract

The solar cycle is not regular. The strength as well as the period varies from cycle to cycle. One puzzling aspect of this sunspot cycle is the Maunder minimum in 17th century when sunspots disappeared for about 70 years. Indirect studies suggest that there were several other such events in the past. The motivation of my talk will be first to understand the generation and the evolution of the large-scale magnetic field of the Sun and then to model some irregular features of the solar cycle. I shall discuss a flux transport dynamo model to study the evolution of magnetic fields in the Sun. In this model, the toroidal field is generated by the strong differential rotation near the base of the convection zone and the poloidal field is generated near the solar surface from the decay of sunspots. The turbulent diffusion, the meridional circulation and the turbulent pumping are the important flux transport agents in this model which communicate these two spatially segregated source regions of the magnetic field. With this dynamo model, I shall explain several aspects of the solar cycle including grand minima. I shall also discuss the predictability of the future solar cycle using dynamo models

The CHACE that never ends!

Date: 2013-02-04
Speaker: Prof. R. Sridharan
Venue: Ground Floor Lecture Hall

Abstract

It is known that the unique experiment in the Moon Impact Probe of Chandryaan-1 had yielded the first direct evidence for the presence of water vapour in addition to revealing an atmosphere, though tenuous it is, dominated by CO2. Further analysis of the unique data set gives clues to the possible processes in the Lunar interior. In addition, the possible breathing like behaviour of the Lunar regolith is hypothesized based on the CHACE results. So much information seems to be buried in the high quality data, the real CHASE never seems to end!

Demise of the Grand Unified Scheme of Powerful Radio Sources

Date: 2013-01-31
Speaker: Dr. Ashok K. Singal
Venue: Room # 114 (Thaltej Campus)

Abstract

In the currently popular orientation-based unified scheme (OUS), a radio galaxy appears as a quasar when its principal radio-axis happens to be oriented within a certain cone opening angle around the observer's line of sight. Due to geometrical projection, the observed sizes of quasars should therefore appear smaller than those of radio galaxies. We show that this simple, unambiguous prediction of the unified scheme is not borne out by the actually observed angular sizes of radio galaxies and quasars. Thus OUS is ousted. It seems that no straightforward modification, including an evolution of source properties with luminosity or cosmic epoch, could within the current model make it compatible with observations, and to resolve the dichotomy of radio galaxies and quasars, a scheme totally different from the present would be required.

Unification of various Streams of Theoretical Solar Physics

Date: 2013-01-30
Speaker: Prof M.H. Gokhale
Venue: USO Seminar Hall

Abstract

The Cretaceous Volcanic Episode in and around Peninsular India

Date: 2013-01-29
Speaker: Dr. K. S. Misra
Venue: Ground Floor Lecture Hall

Abstract

Streams of Theoretical Solar Physics

Date: 2013-01-29
Speaker: Prof M.H. Gokhale
Venue: USO Seminar Hall

Abstract

Oxidation capacity influenced by convection

Date: 2013-01-28
Speaker: H. Harder
Venue: Ground Floor Lecture Hall

Abstract

Energy release processes during precursor and main phase emission in Solar flare

Date: 2013-01-24
Speaker: Arun K. Awasthi
Venue: Room # 114 (Thaltej Campus)

Abstract

The time evolution of energy release in solar flare is categorized in three phases viz: precursor, impulsive and gradual. The impulsive and gradual phase of energy release in solar flare are studied in greater detail but the underlying processes of energy release and their relationship with the precursor phase is in debate. The high spatial, spectral and temporal resolution observations are the constraint in this investigation. Observations from current space mission enable to undertake extensive study of the precursor phase and relationship with the whole flare energetics. I will discuss study carried out by me related to the physical processes occurring in the pre-flare plasma responsible for triggering the main phase of energy release in solar flares and propose the model to improve the understanding of the relationship between precursor and main phase energetics.

Black hole membrane paradigm

Date: 2013-01-24
Speaker: Dr. Sudipta Sarkar
Venue: Room No. 469

Abstract

Black hole membrane paradigm is an alternative way to look at the classical dynamics of black hole horizon in terms of a fluid membrane. In this talk, I present the formal construction of the membrane paradigm for black objects in general relativity and then to Einstein-Gauss-Bonnet gravity. I also discuss the derivation of the stress-tensor for this membrane fluid and study the perturbation around static backgrounds to express the stress tensor in the form of a Newtonian viscous fluid with pressure, shear viscosity and bulk viscosity. Next I will discuss the relationship between membrane paradigm and AdS/CFT conjecture, in particular the violation of so called KSS bound for the ratio of shear viscosity to entropy density in modified gravity theories. The talk will be based on the reference: arXiv:1107.1260 .

A study of North-South asymmetry of sunspot areas during cycle 23 and 24

Date: 2013-01-17
Speaker: Dr. Partha Chowdhury,
Venue: Room # 114 (Thaltej Campus)

Abstract

Sunspots are strongly magnetized regions on the solar surface and are the seats of solar magnetic storms like solar flares and coronal mass ejections – that eject large amounts of magnetized plasma into the space generating hazardous effects to satellites and modern day technologies. Although solar activity appears reasonably symmetric in the two hemispheres after short-term variations are averaged, some cycles have been found to be stronger in one hemisphere. The N-S asymmetry is important for the topology of the interplanetary space, and it influences both interplanetary and near-Earth space parameters. An understanding of hemispheric variation of solar activity may provide insight into the complex dynamic behavior of the solar dynamo in the two hemispheres. In the present work, we study the statistical significance of north–south asymmetry of sunspot areas for the complete cycle 23 and the ascending phase of current cycle 24. The preferred hemisphere in each year of cycle 23 and 24 has been identified. The statistically significant intermediate-term periodicities of the north-south asymmetry of sunspot data have also been investigated. Power spectrum analysis have shown a number of short and mid-term periods including the Rieger type in both cycles 23 and 24.We have also investigated the present strength of current cycle 24 and a comparative study has been done about different previous predictions regarding the strength of this cycle. We present our results and discuss their possible explanations with the help of theoretical models and previous results.

The structure and evolution of protoplanetary disks : Spitzer IRS survey of young stars in the nearby star forming regions

Date: 2013-01-15
Speaker: Dr. Puravankara Manoj
Venue: Room # 114 (Thaltej Campus)

Abstract

Planetary systems are thought to be formed out of protoplanetary disks surrounding young stars. We have obtained 5- 40 micron mid-infared spectra of some 600 protoplanetary disks around young solar-mass stars in the nearby star forming regions of Taurus-Auriga, Chamaeleon I, Ophiuchus and Orion A, with the infrared spectrograph (IRS) on board the Spitzer space telescope. The shape of the mid-infrared continuum and the dust emission features seen in the IRS spectra of such a large sample allow us to study the structure of protoplanetary disks and disk evolutionary indicators that mark the onset of planet formation process such as dust grain growth, sedimentation and crystallization in unprecedented detail. I will describe our analysis and present our main results. I will discuss the implications of these results and the new insights that they provide on our understanding of disk evolution and planet formation.

Spatial distribution of Spontaneous Parametric Down-Converted Photons

Date: 2013-01-10
Speaker: Shashi Prabhakar
Venue: Room No. 469

Abstract

Spontaneous parametric down-conversion (SPDC) is a nonlinear optical process in which photons from a laser beam can split into two lower frequency photons. This photon pair is generated simultaneously and lies on the periphery of a circle, satisfying conservation of energy and momentum. These photon pairs are often used in quantum information experiments and applications like quantum cryptography and Bell's inequality test experiments. In this talk, I will discuss spatial distribution of the parametric down-converted photons for a Gaussian and an optical vortex as pump beams. I have observed that the spatial distribution widens linearly with increasing the size of Gaussian pump beam. The spatial distribution of intensity for a vortex shows up in its down-conversion as well and varies with the order of vortex.

Chromospheric Magnetic Field of the Sun

Date: 2013-01-09
Speaker: Prof. Debi Prasad Choudhary
Venue: Room # 114 (Thaltej Campus)

Abstract

After one hundred year of discovery of magnetic field in sunspots, several outstanding questions related to the origin of explosive events at these locations remain unanswered. In the mean time, many sun like stars have have been found to display super flares, understanding of which need an intensive study of solar phenomena. The key to further advance the field of solar explosion science is observational study of three dimensional magnetic field configuration of active regions. While, in the past measurements mostly focused magnetic field in the photospheric heights, many future instruments plan chromospheric observations. In this presentation, we shall review the current understanding of solar chromospheric magnetic field.

Three-dimensional Structure of Inner Heliosphere during Solar Cycles 22-24

Date: 2013-01-07
Speaker: Prof. P. K. Manoharan
Venue: Room # 114 (Thaltej Campus)

Abstract

The inner heliosphere, which can be defined as the region of space beyond the solar corona and out to ~5 AU, is highly structured on all observable scales. Moreover, the large-scale ambient structure of the inner heliosphere is dominated by interactions between ambient solar wind and (i) high-speed streams from coronal holes (e.g., corotating interaction regions, CIRs) (ii) coronal mass ejections (CMEs). This knowledge is based on the interpretation of a wide array of remote and in situ measurements. In this talk, I will review our current knowledge of the three-dimensional structure of the quasi-steady, large-scale inner heliosphere during solar cycles 22 24. A downward trend in density turbulence has been observed from the maximum of cycle 22 to the deep minimum phase of cycle 23 and beyond. Moreover, the latitudinal distribution of solar wind speed has been significantly different during the above period. I will highlight the properties of the peculiar solar minimum, which has been, thus far, quite distinct.

Vertical coupling in atmospheres as seen in the thermospheric dayglow emissions

Date: 2013-01-07
Speaker: Fazlul Islam Laskar
Venue: Fourth Floor Lecture Hall

Abstract

Disks and Outflows around Massive YSOs

Date: 2013-01-03
Speaker: Dr. Bhargav Vaidya,
Venue: Room # 114, Thaltej Campus

Abstract

The inner most regions around massive young stellar objects (YSO) are associated with complex interactions between numerous physical processes. Since the inner few Astronomical Units (AU) are tough to resolve observationally, a theoretical approach is important to create a qualitative picture for these regions around young high-mass stars. In this talk, I will focus on the interplay between important physical processes with respect to the dynamics of jets and inner accretion disks. In particular, I will discuss the applicability of a thin accretion disk model with proper dust and gas opacity for a luminous young high-mass star. Further, I will examine the stability of such inner accretion disks and argue that they form an ideal launching base for long-lasting outflows. Outflows and jets are an ubiquitous phenomenon in young massive star forming regions. Observational surveys have suggested that the outflows become wider as the star grows in luminosity (thus mass) with time. In this talk, I will present results from magneto-hydrodynamic (MHD) simulations of wind launching in presence of radiative forces from the luminous star and the inner hot accretion disk. The major outcome of this work, is that the radiative force from the central star plays a dominating role in accelerating and de-collimating the magnetically launched jet, while the influence of the disk radiative force is rather small. This interplay of radiative and magnetic forces provides a physical insight to the trend in degree of collimation suggested by observations. Lastly, I will apply this model of MHD wind driving to study a particular outflow from a

Atmospheric outflow from the Indo-Gangetic Plain

Date: 2013-01-01
Speaker: Dr. M. M. Sarin
Venue: Ground Floor Lecture Hall

Abstract

2012

Long-term changes in stratospheric electrical conductivity based on balloon-borne measurements: comparison with theory

Date: 2012-12-31
Speaker: S.P. Gupta
Venue: Fourth Floor Lecture Hall

Abstract

Pulsars as potential continuous gravitational wave emitters

Date: 2012-12-28
Speaker: Dr. Tarun Jha
Venue: Room No. 469

Abstract

Upcoming interferometric detectors such as LIGO, LISA, etc. employed to detect Gravitational Waves (GW), are also expected to detect continuous Gravitational Waves from rapidly rotating neutron stars. In the talk we will look at the perspective of locating potentially detectable GW's from pulsars on the basis of their constitution and structure in a field theoretical basis.

LHC and CMS: A look at the future

Date: 2012-12-27
Speaker: Prof. Sunanda Banerjee
Venue: Room No. 469

Abstract

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Aerosols over an urban region: Characteristics and Contribution

Date: 2012-12-24
Speaker: S. Ramachandran
Venue: Fourth Floor Lecture Hall

Abstract

Classical dynamics as an eigenvalue problem

Date: 2012-12-20
Speaker: Prof. R. K. Varma
Venue: Room No. 469

Abstract

A probability amplitude formalism is presented which casts classical dynamics as an eigenvalue problem in the spirit of the Schrodinger formalism. The governing equation of the formalism is a first order partial differential for a probability amplitude in contrast to the second order of the Schrodinger equation. A solution for the amplitude for a given dynamical problem yields, in a rather straightforward way, the solution for the Hamilton principal function, which is a solution of the Hamilton-Jacobi equation; whence the trajectory determination follows with the H-J prescription. The linearity of the eigenvalue equation offers a great operational advantage for the treatment of perturbations as against the usual procedure using the (nonlinear) Hamilton-Jacobi equation in the action-angle framework.

Particle export during the iron fertilization experiment LOHAFEX

Date: 2012-12-18
Speaker: Dr. R. Rengarajan
Venue: Ground Floor Lecture Hall

Abstract

Vacuum Stability constraints on the minimal singlet TeV Seesaw Model

Date: 2012-12-13
Speaker: Subrata Khan
Venue: Room No. 469

Abstract

We consider the minimal singlet seesaw model in which two gauge singlet right handed neutrinos with opposite lepton numbers are added to the Standard Model. In this model, the smallness of the neutrino masses is explained by tiny lepton number violating coupling betweenone of the singlets with the standard left-handed neutrinos. This allows one to have the the right handed neutrino mass at the TeV scale as well as appreciable mixing between the light and heavy states. This model is fully reconstructible in terms of the neutrino oscillation parameters apart from the overall coupling strengths. In this paper we show that the overall coupling strength 'y_nu' for the Dirac type coupling between the left handed neutrino and one of the singlets can be restricted by consideration of the stability bounds on the Higgs potential. Incorporating this bound, the overall coupling strength of the lepton number violating coupling can also be constrained from neutrino oscillation data. In this model the lepton flavour violating decays of charged leptons can be appreciable which can also put constraint on 'y_nu' for right-handed neutrinos at TeV scale. We discuss the combined constraints on 'y_nu' for right-handed neutrinos near TeV scale from the process mu -> e gamma and from the consideration of vacuum stability constraints on the Higgs self coupling. We also briefly discuss the implications for neutrinoless double beta decay and possible signatures of the model that can be expected at colliders.

Indian Summer Monsoon in the Late Pleistocene: Reconstruction from a Speleothem from P. India

Date: 2012-12-11
Speaker: Dr. Timmy Francis
Venue: Ground Floor Lecture Hall

Abstract

Aerosol perturbations over central Himalayas caused by post harvest biomass burning in Punjab

Date: 2012-12-10
Speaker: Shivraj Sahai
Venue: Fourth Floor Lecture Hall

Abstract

LR symmetry Reloaded

Date: 2012-12-06
Speaker: Dr. Joydeep Chakrabortty
Venue: Room No. 469

Abstract

Left-Right symmetry is one of the popular and interesting model around TeV scale. This model is phenomenologically interesting in sens that the scale of this theory is around TeV within well reach of the Large Hadron Collider (LHC) and this model can be embedded in some high scale Grand Unified groups, like SO(10), E(6). I will discuss the impact of low energy constraints on the model parameters. The contribution to Neutrinoless Double Beta Decay process will be discussed in Type-I and Type-II seesaw dominant cases. I will briefly hint the connection and possible contribution to Lepton Flavour Violating processes in Left-Right symmetric Model.

Solar Thermal Applications

Date: 2012-12-05
Speaker: Dr. N. M. Nahar
Venue: Room # 114, Thaltej Campus

Abstract

Paleoclimatic Records from the Northern Indian Ocean

Date: 2012-12-04
Speaker: Dr. Ravi Bhushan
Venue: Ground Floor Lecture Hall

Abstract

Atmospheric dry deposition of mineral dust and anthropogenic trace metals to the N. Indian Ocean

Date: 2012-11-27
Speaker: Dr. Bikkina Srinivas
Venue: Ground Floor Lecture Hall

Abstract

Tropospheric ozone chemistry: Observations and modelling

Date: 2012-11-19
Speaker: Shyam Lal
Venue: Fourth Floor Lecture Hall

Abstract

Neutrino oscillation and present status of sterile neutrino

Date: 2012-11-08
Speaker: Monojit Ghosh
Venue: Room No. 469

Abstract

Neutrino oscillation in standard three flavor picture is now well established from solar, atmosphere, reactor, and accelerator neutrinos. The mass squared differences governing these oscillations are \tilde 10^-4 and 10^-3 eV^2. But recent experimental data is indicative of oscillations governed by mass squared differences ~ eV^2. This requires addition of a fourth light neutrino which must be a sterile. In my talk I will briefly describe the neutrino oscillation in vacuum and present status of sterile neutrino.

A High-precision Measurement System for Carbon Isotopic Ratios of Atmospheric Methane

Date: 2012-11-06
Speaker: Mr. D. K. Rao
Venue: Ground Floor Lecture Hall

Abstract

Importance of Saha equation in LIBS algorithm

Date: 2012-11-05
Speaker: K.P. Subramanian
Venue: Fourth Floor Lecture Hall

Abstract

Recent progresses in viscous hydrodynamics and the shear viscosity of the QGP.

Date: 2012-11-01
Speaker: Dr Victor Roy
Venue: Room No. 469

Abstract

One of the most important finding in the recent years at both Relativistic heavy ion collider (RHIC) and at Large Hadron Collider (LHC) is the existence of a strongly interacting almost perfect nuclear fluid which is produced in high energy heavy ion collision. Both Lattice QCD and string theoretical calculation of the transport properties of the QCD matter at high density and temperature shows that the ratio of shear viscosity to entropy density (η/s) of the QCD matter reaches a very low value which is believed to be the lowest among all known fluids. However, these theoretical calculations contain large uncertainties. One can also estimate the value of transport coefficients (shear, bulk viscosity) of QCD matter by means of phenomenological model study e.g, relativistic viscous hydrodynamics. However, the extracted value of η/s from viscous hydrodynamics relies on some strong assumption about the initial conditions as well as other input parameters used in the model. In this talk I will mainly focus on the recent progresses in the field of viscous hydrodynamics to extract the value of η/s from the experimental data. I will also discuss some open problems related to viscous hydrodynamics which immediately needs attention in order to precisely estimate the value of $\eta/s$ from experimental data.

Detection of long living neutral hydrated clusters in laboratory simulation of ionospheric D-region plasma

Date: 2012-10-29
Speaker: H.S.S. Sinha
Venue: Fourth Floor Lecture Hall

Abstract

Present Status of Nuclear Quadrupole Moments in [39-41]-K Isotopes

Date: 2012-10-26
Speaker: Yashpal Singh
Venue: Room No. 469

Abstract

Quadrupole moment (Q) of an atomic nucleus describes the effective ellipsoidal charge distribution inside the nucleus. There is no direct experimental technique available to measure this quantity, however using nuclear models, it is possible to estimate Q of different isotopes, but currently there is no such standard nuclear model which can predict this quantity precisely. By combining measurements of atomic hyperfine structure splitting with the corresponding calculations, it is possible to infer the model independent value of Q in an atomic system. Provided both the measurement and the calculated result are very accurate, the obtained Q value will be very precise which can further used to test against the results obtained by different nuclear models. In the present, talk we shell discuss the recently reported values of Q in [39-41]-K isotopes which differ significantly from the known standard values in the literature.

Lamont-Doherty Earth Observator

Date: 2012-10-23
Speaker: Prof. R. F. Anderson
Venue: Ground Floor Lecture Hall

Abstract

Quantitative elemental analysis using LIBS

Date: 2012-10-22
Speaker: Prashant Kumar
Venue: Fourth Floor Lecture Hall

Abstract

Solid Earth Geophysics in India Since Independences

Date: 2012-10-16
Speaker: Prof. R. N. Singh
Venue: Ground Floor Lecture Hall

Abstract

PRL Spectral Radiometer: A new tool to study aerosols

Date: 2012-10-15
Speaker: T.A. Rajesh
Venue: Fourth Floor Lecture Hall

Abstract

Restricted equilibrium ensembles: Exact equation of state of a model glass

Date: 2012-10-10
Speaker: Prof. Deepak Dhar
Venue: Room No. 469

Abstract

We investigate the thermodynamic properties of a toy model of glasses: a hard-core lattice gas with nearest neighbor interaction in one dimension. The time-evolution is Markovian, with nearest-neighbor and next-nearest neighbor hoppings, and the transition rates are assumed to satisfy detailed balance condition, but the system is non-ergodic below a glass temperature. Below this temperature, the system is in restricted thermal equilibrium, where both the number of sectors, and the number of accessible states within a sector grow exponentially with the size of the system. Using partition functions that sum only over dynamically accessible states within a sector, and then taking a quenched average over the sectors, we determine the exact equation of state of this system.

Generation,emplacement and preservation of carbonatites: a story from Rajasthan, India

Date: 2012-10-09
Speaker: Dr. J. S. Ray
Venue: Ground Floor Lecture Hall

Abstract

Core ionisation and fragmentation of molecules using soft X-rays

Date: 2012-10-08
Speaker: Bhas Bapat
Venue: Fourth Floor Lecture Hall

Abstract

Energy-dependent thermal emission in solar flares

Date: 2012-10-04
Speaker: Mr. Arun Kumar Awasthi
Venue: Room # 114, Thaltej Campus

Abstract

Characteristics of aerosol over land and ocean and their radiative impact

Date: 2012-10-01
Speaker: P.R. Sinha
Venue: Fourth Floor Lecture Hall

Abstract

Lee-Wick thermodynamics and its cosmological implications

Date: 2012-09-28
Speaker: Dr. Suratna Das
Venue: Room No. 469

Abstract

Lee-Wick fields were first introduced in the literature as a regulator field to tame the divergences in QED. Recently this theory is used in an extended standard model to solve the "Hierarchy Problem". In this talk the high-temperature behaviour of such Lee-Wick fields will be discussed. It would be shown that at high temperatures these Lee-Wick fields lead to negative energy density and pressure. But, being regulator fields, they are always accompanied with standard particles. Thus the total energy density and pressure of particles and their Lee-Wick partners turn out to be positive and yield a fluid with state parameter ω=1. In the second part of the talk it would be shown that such a fluid can dominate the universe just before the standard radiation domination era sets in.

Is Interstellar Space Travel Possible?

Date: 2012-09-27
Speaker: Dr. Ashok K. Singal
Venue: Room # 114, Thaltej Campus

Abstract

In Quest of the Knots: Revisiting Chronotopic Crossroads

Date: 2012-09-27
Speaker: Dr. Annapurna Rath
Venue: Room No. 469

Abstract

Time-Space interrelationships comprise the fundamental knots of human existence. To understand the problems concealed within the conflicting yet symbiotic relationships of the time-space grid has been the core quest of theoretical enterprises across disciplines – Physics, Philosophy, and Mathematics. Creative enterprises have their own unique ways of understanding the time-space grid. The never ending dialogue between temporal and spatial axes is explored in the conceptual thread of the “Chronotopes” proposed by the Russian thinker Mikhail Bakhtin. Through this talk, I would attempt to explore the theoretical foregrounding that go into defining the chronotopes as not only conceptual categories, but rather as a step towards interdisciplinary endeavor -- an attempt to bridge the gap between philosophy and science, between “mind” and “matter”.

Theoretical Perspectives on a 125 GeV Higgs Boson

Date: 2012-09-25
Speaker: Sreerup Raychaudhuri
Venue: Room No. 469

Abstract

Assuming that the new boson recently discovered at CERN is the long-sought Higgs boson, the impact of this discovery on the Standard Model, on the future of LHC and on physics beyond the Standard Model will be discussed, from the perspective of a theorist.

Radiation pressure instability in unstable disks showing 'heartbeats'

Date: 2012-09-21
Speaker: Ms. Anjali Rao
Venue: Room # 114, Thaltej Campus

Abstract

A generic constraint on non-minimal coupling in inflationary cosmology

Date: 2012-09-11
Speaker: Abhishek Basak
Venue: Room No. 469

Abstract

We study the first order perturbations in a non-minimally coupled scalar field theory in the Jordan frame. It is shown by comparing the expression for the spectral index nr with the observed value that the non-minimal coupling constant ξ can have an upper bound. The bound on ξ is generic as it is obtained without assuming any specific form of potential. Source of this bound is due to the presence of λ1=f˙Hf term in the Friedman equation, where f signifies the non-minimal coupling term. From the Einstein's equation it is shown that the comoving curvature perturbation depends on parameter λ1 and it would evolve on the super horizon scales unless the bound on ξ is imposed.

Effects of Solar X-ray flares on the atmosphere and habitability of Mars

Date: 2012-09-10
Speaker: S.A. Haider
Venue: Fourth Floor Lecture Hall

Abstract

Advances in radiocarbon detection methods

Date: 2012-09-04
Speaker: Dr. M. G.Yadav
Venue: Ground Floor Lecture Hall

Abstract

Effect of dust and SEP events on the Martian Ionosphere

Date: 2012-09-03
Speaker: Varun Sheel
Venue: Fourth Floor Lecture Hall

Abstract

Study of vacuum stability in Type-III seesaw model and its phenomenological consequences at the LHC

Date: 2012-08-30
Speaker: Gaurav Tomar
Venue: Room No. 469

Abstract

ATLAS and CMS collaboration recently announced the discovery of new boson having mass in the range of 124-127 GeV. The vacuum stability condition of the Standard Model potential with this Higgs mass puts an upper bound on the Dirac mass of the neutrinos in Type III seesaw. We have studied this constraint with the TeV scale triplet fermions. In this talk I will discuss the implications of vacuum stability bound with the neutrino less double beta decay and lepton flavour violation process.

Cosmogenic radioactivity in Indian Meteorites collected in last two decades

Date: 2012-08-28
Speaker: Dr. A. D. Shukla
Venue: Ground Floor Lecture Hall

Abstract

Advances in solid state photon detectors (Part II)

Date: 2012-08-27
Speaker: Y.B. Acharya
Venue: Fourth Floor Lecture Hall

Abstract

Bose-Hubbard Models: Quantum Phases, Transitions, and Patterns

Date: 2012-08-23
Speaker: Prof. Ramesh V. Pai
Venue: Room No. 469

Abstract

In my talk, I shall present an extensive study of Mott insulator (MI) and superfluid (SF) shells in Bose-Hubbard (BH) models for bosons in optical lattices with harmonic traps. For this we apply (i) the inhomogeneous mean-field theory for 2 and 3-D and (ii) numerical density matrix renormalization group for 1-D. Our results for the BH model with one type of spinless bosons agree quantitatively with quantum Monte Carlo simulations. Our approach is numerically less intensive than such simulations, so we are able to perform calculations on experimentally realistic, large three-dimensional systems, explore a wide range of parameter values, and make direct contact with a variety of experimental measurements. We also extend our inhomogeneous mean-field theory to study BH models with harmonic traps and (a) two species of bosons or (b) spin-1 bosons. With two species of bosons, we obtain rich phase diagrams with a variety of SF and MI phases and associated shells when we include a quadratic confining potential. For the spin-1 BH model, I shall show in my talk, in a representative case, that the system can display alternating shells of polar SF and MI phases, and we make interesting predictions for experiments in such systems.

A first-time detection of giant pulses from a normal-period pulsar B0950+08

Date: 2012-08-16
Speaker: Dr. Ashok K. Singal
Venue: Room # 114, Thaltej Campus

Abstract

Grand unification in the light of LHC

Date: 2012-08-16
Speaker: Prof. David Miller
Venue: Room No. 469

Abstract

-NA-

Radiocarbon dating of groundwater

Date: 2012-08-14
Speaker: Mr. Balaji D.
Venue: Ground Floor Lecture Hall

Abstract

Mesospheric Temperature Inversions: Interplay between dynamical and chemical processes

Date: 2012-08-13
Speaker: Som Kumar Sharma
Venue: Ground Floor Lecture Hall

Abstract

Molybdenum isotopes in the Indian Estuaries: Implication to biogeochemistry of Mo

Date: 2012-08-07
Speaker: Dr. Sunil Kumar Singh
Venue: Ground Floor Lecture Hall

Abstract

Advances in solid state photon detectors (Part I)

Date: 2012-08-06
Speaker: Y.B. Acharya
Venue: Ground Floor Lecture Hall

Abstract

The enigma of Cuprate high-temperature superconductivity: clues from infrared optical conductivity

Date: 2012-08-03
Speaker: Navinder Singh
Venue: Room No. 469

Abstract

Recently, K. Y. Yang, T. M. Rice, and F. C. Zhang (YRZ) have proposed an ansatz for electron Green's function in the pseudogap and superconducting states of Cuprate high temperature superconductors based upon their previous study of Renormalized Mean Field Theory (RMFT) of Cuprates. This RMFT captures the essence of Phil Anderson's Resonance Valence Bond (RVB) model of Cuprates that is based on the strong electron-electro correlation effects. We apply YRZ ansatz to compute optical conductivity using Green's function formulation of Kubo formula. In the over-doped region, optical properties of the Cuprate superconductors agree, qualitatively, with BCS form for d-wave pairing. But in the pseudogap regime a number of anomalous features appear not explainable by BCS form (due to strong electron-electron correlation). We analyze the development of pseudogap and superconducting gap with the variation of temperature and doping. Our results qualitatively agree with the measurements. An effort will be made for pedagogical presentation.

The Physics Potential of future atmospheric Neutrino Detectors

Date: 2012-08-03
Speaker: Raj Gandhi
Venue: Room No. 469

Abstract

-NA-

Towards understanding the pattern of Late Quaternary Glaciations in Indian Himalaya

Date: 2012-07-31
Speaker: Dr. Sheikh Nawaz Ali
Venue: GROUND LECTURE HALL

Abstract

Kinetic Physics of a Turbulent Plasma (aka The Super Awesome Solar Wind)

Date: 2012-07-26
Speaker: Dr. Tulasi Parasar
Venue: Room No. 469

Abstract

It is important to study the nature of the solar wind in order to better understand space weather. The solar wind is observed to be turbulent and understanding its nature and origins requires an understanding of the kinetic physics of turbulent collisionless plasmas. We study collisionless plasma turbulence using PIC hybrid code (particle protons and fluid electrons) and discuss a few aspects of kinetic physics in such systems. We concentrate on kinetic dissipative processes and compare the relative strengths of such processes in the strong 2D limit of plasma turbulence. We also discuss the effects of expansion on solar wind plasma.

Correlated Switching in the Radio and X-ray Emission Properties of Pulsar B0943+10: Evidence for Rapid, Global, Magnetospheric Changes revealed by XMM-Newton, GMRT and LOFAR

Date: 2012-07-23
Speaker: Prof. Willem Hermsen
Venue: Room # 114, Thaltej Campus

Abstract

Why IGR J17091-3624 is so faint? Constraints on distance, mass and spin from phase-resolved spectroscopy of 'heartbeat oscillations'

Date: 2012-07-23
Speaker: Ms. Anjali Rao
Venue: Room # 114, Thaltej Campus

Abstract

Three dimensional scattering of NN potential Argonne V18 without partial waves.

Date: 2012-07-19
Speaker: Saravanan Veerasamy
Venue: Room No. 469

Abstract

The formalism for solving the Lippmann-Schwinger equation in momentum space without partial waves, the new symbolic techniques developed for the analytical treatment of spin degrees of freedom are discussed in the seminar. A realistic NN potential Argonne V18 is used for the computation. The numerical techniques developed for efficient computation of Argonne V18 NN potential in momentum space is also discussed. Finally, the scattering observables computed in this method is presented and compared to calculations using partial waves.

Development of Ionospheric radio technqiues: A historical review (Part I)

Date: 2012-07-09
Speaker: Harish Chandra
Venue: Ground Floor Lecture Hall

Abstract

Extreme values and records: from statistics to physics

Date: 2012-07-09
Speaker: Arul Laxminarayan
Venue: Room No. 469

Abstract

While the study of the ``average" leads to the Central Limit Theorem, there exists similar universal distributions for the largest and the smallest. Indeed the study of Extreme events, Large deviations and Records is of wide interest and there has been a resurgence of interest in these areas with developments from Mathematical Physics to Nonequilibrium Statistical Physics. The talk will be a very limited review of some of these aspects, and its applications to some quantum problems, especially related to quantum chaos and entanglement.

Probing the Brown Dwarf Desert

Date: 2012-07-05
Speaker: Ms. Priyanka Chaturvedi
Venue: Room # 114, Thaltej Campus

Abstract

Field Theory and its applications to Cosmology (including Dark Energy)

Date: 2012-07-05
Speaker: Dr. Anupam Singh
Venue: Room No. 469

Abstract

Field theory is a fundamental tool of physics which I will argue has good reasons to be and could be the lingua franca of all physicists. Of course, if we are to test this claim then it becomes natural to demand that such a lingua franca be capable of describing the physics of our entire Universe (with perhaps some small exception made to the very early Universe). I will therefore describe field theory in the general context of a curved space-time which allows us to address a wide range of topics. I will then focus on one particular application in particular: Dark Energy. This is done not just because Dark Energy makes up about three quarters of the total energy density of the Universe but also because it is one of most fascinating mysteries of our times for which the final chapter is far from being completely finished.

Breit interaction effects in many electron atoms

Date: 2012-07-03
Speaker: Siddhartha Chattopadhyay
Venue: Room No. 469

Abstract

For high accuracy atomic calculations we need to go beyond the Coulomb interaction between two electrons. The next order of interaction is the Breit interaction, which is due to the exchange of transverse photons between two electrons. In this talk I shall discuss about the matrix elements of Breit interaction and the self consistent treatment of the frequency independent Breit interaction in many electron atoms. I will also present some results of Breit contribution at the correlation energy of closed shell atoms based on the many body perturbation theory calculations. At the end I will discuss about the implementation of Breit interaction in the relativistic coupled-cluster theory.

Moving towards the operational forecasting of the occurrence of L-band scintillations based on background TEC variability : a reality?

Date: 2012-07-02
Speaker: Mala Bagiya
Venue: Ground Floor Lecture Hall

Abstract

Dark Matter in two real scalar singlet model with Z2×Z′2 symmetry and a possible explanation of low and high mass WIMPs

Date: 2012-06-28
Speaker: Debasish Majumdar
Venue: Room No. 469

Abstract

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Compton polarimeter as a focal plane detector for hard X-ray telescope: Sensitivity estimation with Geant4 simulations

Date: 2012-06-26
Speaker: Mr. Tanmoy Chattopadhyay
Venue: Room # 114, Thaltej Campus

Abstract

Solar variations, rotations and their impact on the Earth's atmosphere

Date: 2012-06-25
Speaker: Satish Chandra
Venue: Ground Floor Lecture Hall

Abstract

Probing quark gluon plasma (QGP) through electromagnetic radiations

Date: 2012-06-21
Speaker: Jajati K. Nayak
Venue: Room No. 469

Abstract

Heavy nuclei like Pb(Lead)+Pb, In(Indium)+In \& Au(Gold)+Au are collided at very high energies at Super Proton Synchrotron (SPS), CERN, Geneva and at Relativistic Heavy Ion Collider (RHIC), Brook Haven National Laboratory, USA aiming to create the novel state of matter quark gluon plasma (QGP). The matter created at the relativistic nuclear collisions emits different radiations. To diagonise the matter using the electromagnetic radiations such as photons and lepton pairs are more advantageous because of their nature of interactions with the medium they are produced. Here we discuss the photon and lepton pair productions from Pb+Pb, In+In and Au+Au collisions in terms of invariant spectra at different colliding energies. The thermodynamic informations like the initial temperature of the matter has been inferred from the evaluation of the spectra and it has been found that the inferred temperatures for the above SPS and RHIC energies are larger than the transition temperature (Tc) of the hadronic matter to QGP as predicted by lattice quantum chromodynamics (lQCD) at zero baryonic chemical potential.

Relativistic hydrodynamics and shear viscosity driven instability in Quark-Gluon Plasma

Date: 2012-06-20
Speaker: Avdhesh Kumar
Venue: Room No. 469

Abstract

In this Seminar I shall discuss about the relativistic Hydrodynamics and its application to relativistic heavy ion collisions. While keeping keeping its applications in mind, Further I shall discuss about the viscosity driven instabilities in the heavy ion collision dynamics.

Neutrino mass and multilepton signatures at LHC from a model of dimension 7 operator

Date: 2012-06-19
Speaker: Gulab Bambhaniya
Venue: Room No. 469

Abstract

Neutrino oscillation experiments suggest nonzero neutrino masses. In the Standard Model(SM) neutrinos are massless. Therefore one has to go beyond SM. There are conventional seesaw mechanisms from which scale of new physics is very high (1014 GeV) and this scale is out of collider reach. I will talk about a model in which neutrino mass at tree level can be generated from dimension 7 operator and hence the scale of new physics is at TeV scale which can be explored at collider like LHC. Then I will tell about multilepton signature from this model at LHC.

Halogens in the Earth's atmosphere : An overview

Date: 2012-06-18
Speaker: Lokesh Kumar Sahu
Venue: Ground Floor Lecture Hall

Abstract

IWOP Technique and operator orderings

Date: 2012-06-18
Speaker: Nigam Lahiri Samantray
Venue: Room No. 469

Abstract

In quantum optics, operator ordering is one of the fundamental tasks in obtaining expressions for various states of light and also in calculating the expectation values of operators in these states. In this talk I will explain the newly developed IWOP (Integration Within Ordered Product) technique for arranging operators into ordered products (normal, anti-normal, Weyl)

Quadratic Gravity and Galactic Rotation Curves

Date: 2012-06-18
Speaker: Girish Chakravarty
Venue: Room No. 469

Abstract

Under the standard cosmological model based on FLRW geometry, in addition to the baryonic matter, the dark matter and the dark energy are need to be invoked to account for the total energy density of the universe. For many years it has been believed that if the gravity is governed by General Relativity field equations, there should be a substantial amount of non-luminuos (dark) matter in the galaxy and galactic clusters to account their observed dynamics.The Newtonian limit of Einstein's equations which is an excellent approximation for the solar and galactic systems cann't account the dynamics of galaxy and galactic cluster without dark matter. Einstein's General Relativity is a theory which has a linear term in the curvature R. In this seminar I shall discuss the quadratic correction to General Relativity and its implication to Galactic Rotation Curves. I shall briefly discuss about inflation in Quadratic Gravity.

Molecular systems: Investigating the nature of stability

Date: 2012-06-11
Speaker: Amrendra Pandey
Venue: Ground Floor Lecture Hall

Abstract

Two zero mass matrices and sterile neutrinos

Date: 2012-06-11
Speaker: Monojit Ghosh
Venue: Room No. 469

Abstract

The complex Majorana neutrino mass matrix in 3 generation contains 9 parameters, all of which can not be determined experimentally. So it is proposed that it may have several zeros. According to the current data, among the possible 15 two zero's, only 7 are allowed. Now in the context of one extra sterile neutrino we tried to look what will happen to those disallowed textures. This can have significant impact on model building with sterile neutrinos.

Renormalization Group Evolution of the Non-Unitary operator

Date: 2012-06-08
Speaker: Subrata Khan
Venue: Room No. 469

Abstract

Integrating out a heavy field gives rise to effective Lagrangian containing higher dimensional operators. In the context of Type-I seesaw mechanism, integrating out the heavy right handed neutrino field leads to unique dimension five operator which gives the tree level neutrino mass term. Apart from these there are dimension six operators that can have important implications. A linear combination of two such operators gives rise to the non-unitarity in the lepton mixing matrix, UPMNS. We discuss the origin of non-unitarity at the high scale and its evolution through renormalization group running.

Variability in Blazars

Date: 2012-06-07
Speaker: Mr. Sunil Chandra
Venue: Room # 114, Thaltej Campus

Abstract

The Nuclear Spectroscopic Telescope Array (NuSTAR)

Date: 2012-06-04
Speaker: Dr. Vikram R. Rana,
Venue: Room # 114, Thaltej Campus

Abstract

Trace gas variations over Bay of Bengal: Effects of transport and chemistry

Date: 2012-06-04
Speaker: Chinmay Mallik
Venue: Ground Floor Lecture Hall

Abstract

Nuclear Spin Dependent Parity Non-conservation from Hyperfine Interaction

Date: 2012-06-04
Speaker: Siddhartha Chattopadhyay
Venue: Room No. 469

Abstract

One source of nuclear spin-dependent (NSD) parity non-conservation (PNC) in atoms is the interference of the hyperfine interaction and the nuclear spin independent (NSI) PNC. We have examined this form of interaction in the frame work of perturbed coupled-cluster theory. In this talk I will briefly discuss in general the sources of NSD-PNC and discuss in some detail the hyperfine interaction perturbed NSI-PNC in atoms. I shall also present preliminary theoretical development to calculate the effect in alkali atoms.

Molecular systems: A theoretical viewpoint

Date: 2012-05-28
Speaker: Amrendra Pandey
Venue: Ground Floor Lecture Hall

Abstract

Study of Vacuum Stability in Seesaw Models

Date: 2012-05-28
Speaker: Gaurav Tomar
Venue: Room No. 469

Abstract

ATLAS and CMS collaborations have narrowed down the allowed range of Higgs mass to the region 115-131 GeV. Additionally there are hints of the Higgs mass being near 125 GeV. Once this discovery is verified, we can investigate the impact of 125 GeV Higgs boson on the search of new physics beyond the Standard Model.We have taken into account the vacuum stability corresponding to a 125 GeV Higgs boson and studied its implication on Seesaw scale. In this talk, I will discuss the vacuum stability implication on Higgs mass, and Seesaw scale. We have studied the TeV scale seesaw mechanism, which can be probed at LHC and we can put bounds on the light neutrinos masses by demanding vacuum stability of 125 GeV Higgs in such models.

Development of optical parametric oscillator (OPO) for entangled photons

Date: 2012-05-25
Speaker: A. Aadhi
Venue: Room No. 469

Abstract

TEntangled photons are of great importance due to their wide applications in many fields including quantum computation and quantum communication. Such entangled photons are commonly generated by spontaneous parametric down conversion (SPDC) of laser radiation in a nonlinear crystal. However, different applications of such photons demand different features. For example, quantum computation may require entangled photons with narrow bandwidth to couple entangled photon with atom while quantum communication may require entangled sources with higher brightness. Unfortunately, single-pass SPDC of continuous-wave or femto-second pump laser do not satisfy the above requirements. Optical parametric oscillators (OPOs), made by coupling SPDC sources inside a high finesse cavity, can generate entangled photons while working below as well as above its threshold. Due to the high finesse of such optical cavities, the generated photons have very low bandwidth and also high brightness, the reason they are called cavity enhanced entangled source. On the other hand, OPOs well above threshold can also be used as alternative coherent source of light for SPDC. In this talk, I will discuss basic principles of the OPO and how it leads to generate Bell's state in polarization basis. I will also discuss about the correlation measurement and quantum tomography technique.

Gyro-orbit size and the implausibility of coherent emission by bunching in synchrotron radio sources

Date: 2012-05-24
Speaker: Dr. Ashok K. Singal
Venue: Room # 114, Thaltej Campus

Abstract

Rayleigh Taylor Instability in anisotropic binary Bose-Einstein Condensates

Date: 2012-05-24
Speaker: Arko Roy
Venue: Room No. 469

Abstract

The two species Bose-Einstein condensate(TBEC) is an excellent candidate to explore non-linear phenomena in superfluids. The remarkable feature of TBEC is the phase-separation, which is non-existent in single species BEC. In this talk, I will discuss about the development of interfacial instability in TBECs, namely, Rayleigh-Taylor instability(RTI). One can initiate and examine RTI in TBEC by changing the intraspecies interaction. The subsequent deformation of the interface into various patterns is an observable signature of RTI. On changing the anisotropy of the trapping potential, RTI can also be inhibited.

Stable dipoles and quadrupoles in photorefractive media

Date: 2012-05-24
Speaker: Pravin Vaity
Venue: Room No. 469

Abstract

Dipole and quadrupole vortex beams are unstable in free space propagation. The vortices in these beams annihilate each other and form crescent kind structure during propagation. However, for propagation through a photorefractive medium they form a stable structure. On the other hand dark rings of LG beam, eigensolution of wave equation in free space, break to form quadrupole vortex in the photorefractive medium. Our results show that dipole and quadrupole vortices may be the solution of nonlinear paraxial wave equation with photorefractive nonlinearity.

Molecular fragmentation : Role of ionization process

Date: 2012-05-21
Speaker: Koushik Saha
Venue: Ground Floor Lecture Hall

Abstract

Precise Estimate of Multipolar Black-body Radiation Shifts in the Atomic Ion Clocks

Date: 2012-05-21
Speaker: Dillip Nandy
Venue: Room No. 469

Abstract

It is not very far to reach the 10−18 fractional uncertainty in the atomic clocks that may redefine the unit of time. Optical transitions with ultranarrow frequencies in the singly positively charged atomic ions are the ultimate choices for the atomic clocks. The major problem in setting up the best accurate atomic clock is lying in the reduction of uncertainties associated with the systematic shifts that the atomic systems undergo during the experiment.To achieve below 10−18 fractional uncertainty in the atomic clocks, it would be prerequisite to estimate the uncertainties that may occur due to the multipolar black-body radiation shifts in these clocks. In the present talk, I will discuss our recent work to estimate these shifts in Ca+ and Sr+ clocks which are under consideration at different laboratories around the world.

Entanglement verification with Bell's inequality

Date: 2012-05-18
Speaker: S.G. Reddy
Venue: Room No. 469

Abstract

Entanglement is one of the interesting phenomena in quantum mechanics. Entangled particles have a lot of applications in various fields such as quantum information, quantum cryptography, quantum teleportation, ghost imaging etc. In our laboratory, we are going to use entangled photon source for ghost imaging, in which we can obtain the spatial information of the object by quantum correlations rather than by capturing the image. To use this source, one needs to verify the entanglement between the photons. Violation of Bell's inequality is one of the best ways to prove the entanglement between two particles. In this talk, I will discuss about Bell's inequality and its violation in quantum mechanics. I will also discuss an experiment in which entangled photon source is used to show the violation of this inequality.

Cosmological Magnetic Field Generation in Higgs-Inflation Model

Date: 2012-05-18
Speaker: Moumita Das
Venue: Room No. 469

Abstract

We study the generation of magnetic field in Higgs-inflation models where the Standard Model Higgs boson has a large coupling to the Ricci scalar. We couple the Higgs field to the Electromagnetic fields via a non-renormalizable dimension six operator suppressed by the Planck scale in the Jordan frame. We show that by choosing the Higgs coupling λ(MZ)=0.132 (which corresponds to mh=126GeV in keeping with the recent measurements by ATLAS and CMS) and curvature coupling ξ(MZ)=103 we can generate comoving magnetic fields of 10−7 Gauss at present and comoving coherence length of 100kpc. The problem of large back-reaction which is generic in the usual inflation models of magneto-genesis is avoided as the back-reaction is suppressed by the large Higgs-curvature coupling.

A study of the role of Lyman beta fluorescence on OI line strengths in Be stars

Date: 2012-05-17
Speaker: Dr. Blesson Mathew
Venue: Room # 114, Thaltej Campus

Abstract

Spontaneous parametric down-conversion process with BBO crystal

Date: 2012-05-17
Speaker: Shashi Prabhakar
Venue: Room No. 469

Abstract

Spontaneous parametric down-conversion (SPDC) is a nonlinear optical process in which photons from a laser beam, with a rather very low probability, can split into two lower frequency photons. In other words, when the input laser photons interact with a non-linear crystal (BBO), one photon of the input laser is down-converted to two lower energy photons. This photon pair is generated simultaneously and lies on the periphery of a circle, satisfying conservation of energy and momentum. If the generated photon pairs have the same polarization, it is called Type-I SPDC and if they have orthogonal polarizations, it is called Type-II SPDC. These photon pairs are often used in quantum information experiments and applications like quantum cryptography and Bell's inequality test experiments. In this talk, I will discuss about the experimental realization of SPDC and spatial distribution of the generated photon pair. I will also discuss about the experiment that we have performed and their results.

Understanding of correlation behaviors in the calculations of atomic dipole polarizabilities using an ab initio many-body perturbation theory

Date: 2012-05-17
Speaker: Yashpal Singh
Venue: Room No. 469

Abstract

It is necessary to go beyond the Hartree-Fock method (even in the relativistic case) to calculate the dipole polarizabilities in the atomic systems accurately. Understanding of the trends and dynamics of the correlation effects will be useful in the determination of these quantities more precisely. In this talk, I will explain an ab initio many-body method to evaluate dipole polarizabilities and highlight contributions from various correlations obtained using this method in few atomic systems. At the end, I will also briefly mention how the present study will berelevant to calculate the enhancement factors accurately for the studies of permanent electric dipole moments (EDMs).

Volcanic sulfur dioxide over the Indo-Gangetic plain

Date: 2012-05-14
Speaker: Chinmay Mallik
Venue: Ground Floor Lecture Hall

Abstract

Energy-Dependent Thermal Emission and Cooling in Solar Flare Plasma

Date: 2012-05-10
Speaker: Mr. Arun Kumar Awasthi
Venue: Room # 114, Thaltej Campus

Abstract

Non standard spinors in inflation and dark energy

Date: 2012-05-10
Speaker: Abhishek Basak
Venue: Room No. 469

Abstract

There are very compelling reasons to believe that our universe might have undergone the phase of accelerated expansion twice in its history. The first phase of accelerated expansion was at a very early time which is called inflation and second phase started recently at around redshift z=1. Dark energy can be behind the late time acceleration. Inflation and dark energy can give us the theoretical understanding of the observation. However the exact nature of inflation and dark energy is not fully understood. There exists several models of inflation and dark energy. Among them time varying scalar field model is extensively studied. In this seminar I will talk about the possibilities of non standard spinors as a candidate of inflation and dark energy.

Study of Carbon Dioxide in the atmosphere

Date: 2012-05-07
Speaker: Naveen Chandra
Venue: Ground Floor Lecture Hall

Abstract

Electron temperature and density measurements in laser produced plasma using Langmuir Probe

Date: 2012-05-03
Speaker: P. Deepa
Venue: Ground Floor Lecture Hall

Abstract

Cold atoms refrigeration of cold ions and cold molecule production in the presence of ions

Date: 2012-05-03
Speaker: S. A. Rangwala
Venue: Room No. 469

Abstract

We experimentally study the cooling of Rb ions in contact with Laser cooled Rb atoms. This experimental result is contrary to the widely held perception that in real ion traps, when ions and atoms have equal masses, the ions would heat out of the trap. We therefore re-examine the theory of collisional cooling of trapped ions by multiple scattering and understand the reasons for trapped ion cooling in this case. Numerical simulations of ion-atom multiple scattering bear out the experimental results. All of these studies show that the resulting ion atom system has an intrinsic stability, which is a crucial result for the prospects of physics with ion-atom mixed system. We shall then discuss the photo-association of molecules from cold atoms in the presence of ions. If time permits the most recent experiments on atom cavity coupling will be discussed, and its relevance to the molecule project explained.

Understanding unimolecular reaction

Date: 2012-04-30
Speaker: Koushik Saha
Venue: Ground Floor Lecture Hall

Abstract

Asymmetry in periodicities of photospheric solar magnetic fields and its implications

Date: 2012-04-26
Speaker: Mr. Susanta Kumar Bisoi
Venue: Room # 114, Thaltej Campus

Abstract

Theory of Langmuir Probe: Evaluation of plasma parameters

Date: 2012-04-26
Speaker: M. Sobhita
Venue: Ground Floor Lecture Hall

Abstract

Perturbed Relativistic Coupled-Cluster Theory for Atomic Calculations

Date: 2012-04-26
Speaker: Siddhartha Chattopadhyay
Venue: Room No. 469

Abstract

The coupled-cluster theory is one of the most reliable quantum many-body theory.It has been used with great success in atomic, nuclear, molecular and condensed matter physics calculations. In the present work, we have developed perturbed relativistic coupled-cluster (PRCC) theory to incorporate the effect of external electric field as a perturbation in the atomic many-body calculations. For this, the coupled-cluster equations for singles and doubles cluster operators are derived and the contributing diagrams are examined. The PRCC operators, obtained by solving the coupled non-linear equations, are then used for the dipole polarizability calculation of closed-shell systems. In this talk, we will examine the results of electric dipole polarizability for noble gas atoms, using the PRCC theory.

Space weather effects over low latitude: An electric field perspective

Date: 2012-04-23
Speaker: D. Chakrabarty
Venue: Ground Floor Lecture Hall

Abstract

Is the Precursor phase a cause to trigger the main phase energy release in Solar flares?

Date: 2012-04-19
Speaker: Mr. Arun Kumar Awasthi
Venue: Room # 114, Thaltej Campus

Abstract

Photons as a probe of both isotropic and anisotropic QGP

Date: 2012-04-19
Speaker: Dr. Lusaka Bhattacharya
Venue: Room No. 469

Abstract

One of the most important issues that arises in the study of relativistic heavy-ion collisions is that of the creation of a new state of matter, quark-gluon-plasma (QGP). Since the plasma life time and volume are small, various ``probes'' of QGP detection have been proposed, such as jet-quenching, photon and dilepton production e.t.c. In this talk the prospect of photons as a possible probe is being discussed.

The build-up to the deep solar minimum between solar cycles 23-24: Earliest inner heliospheric signatures

Date: 2012-04-12
Speaker: Mr. Susanta Kumar Bisoi
Venue: Room # 114, Thaltej Campus

Abstract

Multi-wavelength Variability of Blazars

Date: 2012-04-03
Speaker: Dr. Alok Gupta
Venue: Room # 114, Thaltej Campus

Abstract

The efforts to improve the signal to noise ratio of Lunar Occultation light curves using Wavelet Transforms and Fourier Transforms

Date: 2012-03-29
Speaker: Mr. Tapas Baug
Venue: Room # 114, Thaltej Campus

Abstract

Gesture and speech recognition

Date: 2012-03-12
Speaker: Samarth Shah
Venue: Ground Floor Lecture Hall

Abstract

Current trends and some Examples of CCD and IR Imaging systems

Date: 2012-03-06
Speaker: Prof. Robert Leach
Venue: Room # 114, Thaltej Campus

Abstract

Radiation induced chemistry of interstellar dry ice: Effect of temperature

Date: 2012-02-24
Speaker: B. Sivaraman
Venue: Ground Floor Lecture Hall

Abstract

Coupled cluster method for Energy Spectra and Properties

Date: 2012-02-16
Speaker: Nayana Vaval
Venue: Room No. 469

Abstract

Coupled-cluster (CC) method has emerged as a state of the art method for the accurate calculation of energies and energy derivatives in the atomic and molecular systems. The linear response approach within the CC framework gives atomic and molecular properties very accurately. In this talk, results will be presented for the energy derivatives of molecules with respect to the electric, geometric and magnetic perturbations.

Identification of large scale billows-like structure in the neutral Na layer over Arecibo

Date: 2012-01-30
Speaker: Sumanta Sarkhel
Venue: Ground Floor Lecture Hall

Abstract

Hunt for the Sterile Neutrinos: Present Status and Future Prospects

Date: 2012-01-24
Speaker: Dr. Sanjib Agarwalla
Venue: Room No. 469

Abstract

First I will review the indications in favor of short-baseline neutrino oscillations, which require the existence of one or more sterile neutrinos. Then I will present the results of fits of short-baseline neutrino oscillation data in 3+1 and 3+2 neutrino mixing schemes. Finally I will discuss some powerful future probes to pin down the issue of sterile neutrino oscillation.

CMB TE polarization power spectrum estimation with non-circular beam

Date: 2012-01-12
Speaker: Dr. Subharthi Ray
Venue: Room No. 469

Abstract

Modern CMB experiments are poised for higher multipole survey of the sky and accurate measurement of the angular power spectrum Cl has been a key concern for analysing the data from these experiments. The Maximum Likelihood (ML) estimation technique is optimal but is plagued by the huge computational time and resources when approaching the higher multipoles. So, many alternative methods has been adopted of which the suboptimal but computationally fast pseudo-Cl estimator has been a very feasible approach. A semi analytical work for the pseudo-Cl method taking into account the systematic effect due to the non-circularity of the experimental beam response and has been done previously for the temperature-temperature (TT) co-relation. In the present study, we have extended this technique to the estimation of the cross power spectrum of the temperature and `E' mode (TE) polarized signal, with future plans to extend them to the EE and BB signals also.

2011

How Galilean invariant theories like Navier-Stokes are like gauge theories

Date: 2011-12-29
Speaker: Prof. Arjun Berera
Venue: Room No. 469

Abstract

I will first show how the Navier-Stokes equation (NSE),can be expressed in the same formal language as quantum field theory via thepath integral. The path integral is useful in understanding some aspects of these systems, in particular Ward identities. I show how to calculate such Ward identities for the fluid dynamics equations. This technique has long been used to study the NSE and otherGalilean invariant theories like MHD, Burgers equation and KPZ, howeverthere has been longstanding problems in implementing this method. I show that the origin of these problems is Galilean invariance leads to a redundacy in the path integral similar to that arising from gauge invariance in quantum field theories. I show how this redundacy canbe corrected via the Fadeev-Popov method and then I identify an underlying BRS symmetry in the Navier-Stokes path integral.A focal point of the problems with the Navier-Stokes path integral has been on the issue of how the vertex correlation functionrelates to the response function, and its implications for the nonlinear vertex coupling under renormalization. I show that by our gauge fixing approach, this problem no longer exists.

Some Null-Impedance (Zero-Resistance) Paradoxes in Electrical Circuit Theory

Date: 2011-12-15
Speaker: Dr. Ashok K. Singal
Venue: Room # 114, Thaltej Campus

Abstract

Quantum Transport at Nanoscale: Two Models for Energy and Charge Transfer

Date: 2011-12-12
Speaker: Dr. Malaya Banerjee
Venue: Room No. 469

Abstract

In this talk, I will describe two quantum models which are useful for elucidating energy and charge transfer phenomenology innanoscale junctions. We have employed these models for exploring the dynamics of nonequilibrium quantum dissipative systems, comprising a subsystem coupled to more than one reservoir. Besides the basic interest,practically such systems are the heart of nanodevices and crucial for future progress in nanotechnology. In the energy transfer model, we study the role of quantum effects in the thermal conduction of nonlinear systems, using a self-consistent harmonic chain model, by employing an exact numerical technique, to go beyond the linear response regime. The effect of quantum heat rectification in the mass graded system is also analyzed. In the context of charge transfer, we study the effect of an external magnetic flux on the intrinsic coherence between two electron states through a nanoscale double-dot Aharonov-Bohm interferometer. It is found that the relativephase between the two states of the double dot localizes to specific values due to decoherence.

Mass spectrometry and optical spectroscopy of clusters - preliminary results

Date: 2011-11-28
Speaker: Arvind Saxena
Venue: Ground Floor Lecture Hall

Abstract

Perfect Entanglement Transport in Quantum Spin Chain System

Date: 2011-11-08
Speaker: Dr. Sujit Sarkar
Venue: Room No. 469

Abstract

We propose a mechanism for perfect entanglement transport in anti-ferromagnetic (AFM) quantum spin chain systems with modulated exchange coupling and also for the modulation of on-site magnetic field. We use the principle of adiabatic quantum pumping process for entanglement transfer in the spin chain systems. We achieve the perfect entanglement transfer over an arbitrarily long distance and a better entanglement transport for longer AFM spin chain system than for the ferromagnetic one. We explain analytically and physically - why the entanglement hops in alternate sites. We find the condition for blocking of entanglement transport even in the perfect pumping situation. Our analytical solution interconnects quantum many body physics and quantum information science.

Nonequilibrium Phase Transitions in Active Contractile Filaments

Date: 2011-11-03
Speaker: Dr. Madan Rao
Venue: Room No. 469

Abstract

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Illumination of atomic clusters by intense femtosecond laser pulses

Date: 2011-10-21
Speaker: M. Ranaul Islam
Venue: Ground Floor Lecture Hall

Abstract

Laser Wakefield Accelerator: Towards Gamma-Rays

Date: 2011-10-20
Speaker: Dr. Md. Ranaul Islam
Venue: Room No. 469

Abstract

Particle accelerators are used in many areas of the physical and biological sciences. The conventional accelerators employ radio-frequency electric fields to accelerate charged particles. However, the maximum electric field that can be used is limited by electrical breakdown in the beam pipes, so that accelerating particles to high energies requires a very long accelerator (the largest machine at CERN is 27km in circumference). Laser-driven plasma accelerators offer a way to make particle accelerators much more compact (centimeter range). The attraction of this method, being investigated experimentally and theoretically, lies in the propagation of intense laser pulses in a few cm under-dense plasma, which can accelerate GeV electron beams by utilizing the huge longitudinal electrostatic fields produced by displaced electrons. In a recent work, we have shown that these forces create a bubble-like ion structure, and the transverse restoring force in such ionic-background leads to the emission of intense femtosecond duration gamma-ray betatron radiation [1]. Such femtosecond duration gamma rays could be used to probe the structure of matter on unprecedented length and time scales. [1] S. Cipiccia, M. R. Islam et al. Nature Physics 2011, DOI: 10.1038/NPHYS2090

Study of metal layers occurring in the Mesosphere and Lower Thermosphere (MLT) region of the Earth's atmosphere

Date: 2011-09-19
Speaker: Shikha Raizada
Venue: Ground Floor Lecture Hall

Abstract

The outburst and nature of young eruptive low mass stars in the dark clouds

Date: 2011-09-15
Speaker: Dr. Devendra Ojha
Venue: Room # 114, Thaltej Campus

Abstract

Gas and Dust in the Magellanic Clouds

Date: 2011-09-08
Speaker: Dr. Ananta C. Pradhan
Venue: Room # 114, Thaltej Campus

Abstract

Neutrinoless Double Beta Decay and Heavy Sterile

Date: 2011-08-18
Speaker: Dr. Manimala Mitra
Venue: Room No. 469

Abstract

The experimental rate of neutrinoless double beta decay can be saturated by the exchange of sterile neutrino states, heavier than 200 MeV. This possibility has been analyzed in the context of the Type I seesaw model, performing also exploratory investigations of the implications for heavy neutrino mass spectra, rare decays of mesons, neutrino-decay search, LHC and as well as lepton flavor violation. To obtain saturating contribution from sterile neutrino states, the light- neutrino masses has to be more suppressed than the naive seesaw expectation. We have classified the cases when this condition holds true in the minimal version of the seesaw model, showing its compatibility with neutrinoless double beta rate being dominated by heavy neutrinos and with the allowed light neutrino mass spectra. The absence of excessive fine-tunings and the radiative stability of light neutrino mass matrices provides an upper bound on the heavy neutrino masses of about 10 GeV. We have extended our analysis to the Extended seesaw scenario, where the light and the heavy sterile neutrino contributions are completely decoupled, allowing the sterile neutrinos to saturate the present experimental bound on neutrinoless double beta decay.

Near Infrared Studies of Nova V5579 Sgr

Date: 2011-08-11
Speaker: Mr. Ashish Raj
Venue: Room # 114, Thaltej Campus

Abstract

Optical vortex and its quantum properties

Date: 2011-08-11
Speaker: Shashi Prabhakar
Venue: Room No. 469

Abstract

Vortices are ubiquitous in nature like whirlpool in water, tornadoes and hurricanes. In optics vortices are singular points in the phase distribution of the field and dark points in the intensity distribution. The wavefront is helical in the vicinity of this singular point i.e. it has screw dislocation. The number of windings of the helical wavefront in a unit wavelength of light is known as the order of vortex. There are methods based on interference and diffraction to generate as well as to detect the optical vortices. In this talk, I will discuss and explore an easy method which can provide the order of the vortex and its theoretical and experimental feasibility. Due to helicity in the wavefront, these optical vortices carry orbital angular momentum (OAM). Spontaneous parametric down conversion (a non-linear method) can be used to entangle the OAM states using the conservation of angular momentum of photons. These states provide a platform for the study of higher-dimensional entanglement which is useful in quantum information. In this talk, I will also discuss experimental methods for entanglement of OAM states and its significance.

Dynamics of Equatorial Upper Atmosphere

Date: 2011-08-08
Speaker: Fazlul Islam Laskar
Venue: Ground Floor Lecture Hall

Abstract

Lunar Occultation of a few AGB Stars from Mt. Abu Observatory

Date: 2011-08-04
Speaker: Mr. Tapas Baug
Venue: Room # 114, Thaltej Campus

Abstract

Tribimaximal Mixing From Small Groups.

Date: 2011-08-04
Speaker: Dr. Akin Wingerter
Venue: Room No. 469

Abstract

Current experimental data on the neutrino parameters is in good agreement with tribimaximal mixing and may indicate the presence of an underlying family symmetry. For 76 flavor groups, we perform a systematic scan for models: The particle content is that of the Standard Model plus up to three flavon fields, and the effective Lagrangian contains all terms of mass dimension <=6. We find that 44 groups can accommodate models that are consistent with experiment at 3sigma, and 38 groups can have models that are tribimaximal. For A4xZ3, T7 and T13 we look at correlations between the mixing angles and make a prediction for theta13 that will be testable in the near future. We present the details of a model with theta12=33.9, theta23=40.9, theta13=5.1 to show that the recent tentative hints of a non-zero theta13 can easily be accommodated. The smallest group for which we find tribimaximal mixing is T7. We argue that T7 and T13 are as suited to produce tribimaximal mixing as A4 and should therefore be considered on equal footing. Based on arXiv:1012.2842.

Optical vortices: Finding their charge and propagation through photorefractive materials.

Date: 2011-08-03
Speaker: Pravin Vaity
Venue: Room No. 469

Abstract

We show that measurement of the topological charge and the orbital angular momentum (OAM) of optical vortex can be possible just by using a magnifying glass i.e. a spherical biconvex lens, an ubiquitous optical element found in any optics laboratory. A tilt of the the lens provides us the OAM state of the incident optical vortex. Moreover, this simple operation gives us the helicity of OAM state or the sign of topological charge as well. The experimental results have been verified with exact analytical expression. Then we present the investigation of scattering of optical vortices via beam fanning as they propagate in photorefractive materials. The measurements show that the rate of decay of the intensity depends on the order or topological charge of the vortex. This rate of decay for optical vortices is compared with that of the Gaussian beam which is found to be faster than the vortices. The experimental results are explained using dependence of the two wave mixing or beam coupling in the photorefractive materials on the degree of coherence. The coherence dependence of the beam fanning has been verified with partially coherent light also.

A comprehensive study of the tropospheric chemistry using chemical transport model

Date: 2011-08-01
Speaker: Kabitri Nag
Venue: Ground Floor Lecture Hall

Abstract

Minimal Textures in Seesaw Mass Matrices and their low and high Energy Phenomenology.

Date: 2011-07-28
Speaker: Subrata Khan
Venue: Room No. 469

Abstract

In the context of minimal see-saw framework, we discuss the implications of Dirac and Majorana mass matrices with texture zeros within the type I see-saw mechanism. For the Dirac mass matrices we consider 5 zero textures which we show to be the most minimal form that can successfully account for low energy phenomenology if the Majorana mass matrices are chosen minimal as well. For those, we consider both diagonal and even more minimal non-diagonal forms. Next we discuss the implications of Dirac and Majorana mass matrices in which two properties coexist, equalities among matrix elements in addition to texture zeros. Among the large number of general possibilities, only 12 patterns are found to be consistent with the global neutrino oscillation data at the level of the most minimal number of free parameters. The predictions of the allowed textures for mass hierarchy, θ13 are discussed. We also explore the possibility of having non-zero CP violation for each allowed solution. We find that only one allowed solution can accommodate both low and high energy CP violation. We discuss the prediction of this solution for leptogenesis and explore the correlation, between leptogenesis and low energy CP violation.

Phase diagram and Fluctuations using PNJL model.

Date: 2011-07-21
Speaker: Paramita Deb
Venue: Room No. 469

Abstract

The investigation of the properties of strongly interacting matter at large temperatures and densities is a very active field of research at present.In order to understand the experimantal data from RHIC, LHC, we need a proper theoretical framework. To study the properties of stronglyinteracting matter theoretically, one of the most popular model is Polyakov loopextended Nambu—Jona-Lasinio (PNJL) model. In our work we have investigated thethermodynamic properties like pressure, energy density, specific heat, speed ofsound with this model. We have also studied the phase diagram of PNJL model withsix-quark and eight-quark interactions. The introduction of eight-quark interaction shifts the critical end point (CEP) to the lower chemical potential and highertemperature, which is more closer to the lattice data. Fluctuations and correlations are important signatures of any physical system. We have calculated the fluctuations and correlations of baryon, charge and strangeness quantum number with respect to temperature. The second derivative of pressure show a steep rise near the transition region, which indicates the increase of fluctuation near the transition region. All the fourth order fluctuations show peaks near the transition temperature for six-quark and eight-quark interaction. We have also studied the spectral functions of scalar and pseudoscalar channels just above the transition temperature. The non degenracy between the spectral functions of two channels indicates that U(A)_1 symmetry is not restored just above the transition temperature.

Peculiar motion of the solar system from the sky brightness anisotropy

Date: 2011-07-11
Speaker: Ashok K. Singal,
Venue: Room # 114, Thaltej Campus

Abstract

Transport effects on the distribution of ozone in the troposphere over Ahmedabad

Date: 2011-07-04
Speaker: Shyam Lal
Venue: Ground Floor Lecture Hall

Abstract

Twisting motions in sunspot penumbra: comparison of observations with simulations

Date: 2011-06-30
Speaker: Dr. Lokesh Bharti
Venue: Room # 114, Thaltej Campus

Abstract

Solitons in Nonlinear Optical Fibers and Bose Einstein Condensates Abstract:

Date: 2011-06-28
Speaker: Prof. Prasanta K. Panigrahi
Venue: Room No. 469

Abstract

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Evidence for magneto-convection in sunspot fine structure

Date: 2011-06-28
Speaker: Dr. Lokesh Bharti,
Venue: Room # 114, Thaltej Campus

Abstract

Facility to produce ultra-cold degenerate Bose and Fermi gasses

Date: 2011-06-27
Speaker: Subhadeep De
Venue: Room No. 469

Abstract

I will discuss a new apparatus at the JQI designed to produce mixture of rubidium (87Rb) Bose Einstein condensates (BEC) and degenerate Fermi gasses (DFG) of lithium (6Li) simultaneously. Currently the machine is commissioning the BEC and DFG is in pipeline. There ultra cold Bosons will initially be used for sympathetic cooling of fermions to reach the degeneracy. Degenerate Bose-Fermi mixtures support many quantum phase transitions,giving an experimental platform to study many-body statics, dynamics, andperhaps precision measurements of permanent electric dipole moment.Dynamics of high Tc superconductivity could be realized in ultracoldatoms where Fermions are paired up by boson mediated interactions:hypothetically similar to Cooper pairs. Such induced interaction isenhanced in Rb-Li mixture due to their large mass difference. Rb-Liheteronuclear molecules with large permanent electric dipole moment (4.2Debye) may serve as qubits for quantum computers. In addition, a spin-polarized, non-interacting, degenerate 6Li gas coupledto 87Rb atoms in an optical lattice will give rise to a long range, spin-dependent interactions to realize quantum magnetism and potentially supersolidity. In the experiment red-detuned lattices are far weaker, in recoil units, for 6Li as compared to 87Rb. So in the Mott phase of 87Rb – one atom per lattice site – the 6Li gas hardly feels any lattice potential. In the 87Rb Mott phase the three body recombination of Rb-Li-Li is greatly suppressed and Rb-Li-Li recombination is Pouli blocked. Thus the 10 G wide 87Rb-6Li Feshbach resonance at 1.1 kG is expected to effectively control fermion mediated interactions.

Deformed Shell Model results for double β decay

Date: 2011-05-19
Speaker: Prof. Rankanidhi Sahu
Venue: Room No. 469

Abstract

Double-β decay is a rare weak-interaction process in which two identical nucleons inside the nucleus undergo decay with or without the emission of neutrinos. Two-neutrino double beta decay is fully consistent with the standard model and has been observed in more than 10 nuclei. On the other hand the neutrino less double beta decay which involves emission of two electrons and no neutrinos has not been observed experimentally and violates lepton-number conservation. For the description of double beta decay, one should have a good nuclear structure model for reliably calculating the nuclear transition matrix elements. In the last several years. we have been using the Deformed Shell Model based on Hartree-Fock states to study the spectroscopic properties of the nuclei in the mass 80 region with considerable success. We have successfully described energy spectra, electromagnetic transition probabilities, large ground state deformation, co-existence of shapes, band crossing in many nuclei in this region. In this talk, I will discuss the application of the model to two neutrino double beta decay in 76Ge and 82Se and positron double beta decay in 78Kr, 74Se and 84Sr. In addition, I will present some preliminary results for zero-neutrino double beta decay of 76Ge.

Quantum random walks and spatial search algorithms.

Date: 2011-05-12
Speaker: Prof. Apoorva Patel
Venue: Room No. 469

Abstract

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Ion confinement in Penning traps

Date: 2011-05-02
Speaker: P. Sangeetha
Venue: Ground Floor Lecture Hall

Abstract

Confinement of charged particles by Paul trap

Date: 2011-04-25
Speaker: Remitha V.P.
Venue: Ground Floor Lecture Hall

Abstract

Magnetic Activity in Cool Stars

Date: 2011-04-01
Speaker: Dr. Jeewan C. Pandey
Venue: Room # 114, Thaltej Campus

Abstract

How and why does statistical mechanics work

Date: 2011-03-31
Speaker: Navinder Singh
Venue: Room No. 469

Abstract

As the title says we want to answer the question; how and why does statistical mechanics work? As we know from the most used prescription of Gibbs we calculate the phase space averages of dynamical quantities and we find that these phase averages agree very well with experiments. Clearly actual experiments are not done on a hypothetical ensemble they are done on the actual system in the laboratory and these experiments take a finite amount of time. Thus it is usually argued that actual measurements are time averages and they are equal to phase averages due to ergodicity. Aim of the present review is to show that ergodicity is not relevant for equilibrium statistical mechanics (with Tolman and Landau). We will see that the solution of the problem is in the very peculiar nature of the macroscopic observables and with the very large number of the degrees of freedom involved in macroscopic systems as first pointed out by Khinchin. Similar arguments are used by Landau based upon the approximate property of "Statistical Independence". We review these ideas in detail and in some cases present a critique. We review the role of chaos (classical and quantum) where it is important and where it is not important. We criticise the ideas of E. T. Jaynes who says that the ergodic problem is conceptual one and is related to the very concept of ensemble itself which is a by-product of frequency theory of probability, and the ergodic problem becomes irrelevant when the probabilities of various micro-states are interpreted with Laplace-Bernoulli theory of Probability (Bayesian viewpoint). In the end we critically review various quantum approaches to thefoundations of statistical mechanics. It is argued that the eigenstate thermalization hypothesis is a special case of von Neumann's quantumergodic theory, and analogies are seen in the Khinchin's classical approach and in the von Neumann's quantum approach.

Physical Properties and RV measurements of Late-M Dwarfs

Date: 2011-03-29
Speaker: Dr. Rohit Deshpande
Venue: Room # 114, Thaltej Campus

Abstract

Aerosols and Global-to-Continental-scale Climate Change

Date: 2011-03-22
Speaker: V. Ramaswamy
Venue: Ground Floor Lecture Hall

Abstract

Mass measurements at the LHC with missing particle- challenges and strategies of recent times.

Date: 2011-03-10
Speaker: Partha Konar
Venue: Room No. 469

Abstract

Dark matter as non-standard fundamental particle should be weakly interacting so expected to leave no signals or energy deposits in the detectors at the LHC. Any study of this heavy, neutral, stable missing particles is complex. Recently, there has been a great deal of theoretical effort to explore the nature of dark matter particles at the LHC. In this talk I outline and discuss the mass determination techniques developed lately. I'll also cover my works on this area.

maging observations of coupling processes in the atmosphere-ionosphere-magnetosphere system

Date: 2011-03-07
Speaker: Kazuo Shiokawa
Venue: Ground Floor Lecture Hall

Abstract

Solar Energetic Particles and their Associated CMEs

Date: 2011-03-04
Speaker: Prof. P. K. Manoharan
Venue: Room # 114, Thaltej Campus

Abstract

Radio Observations of Solar Flares and CMEs

Date: 2011-03-03
Speaker: Prof. P. K. Manoharan,
Venue: Room # 114, Thaltej Campus

Abstract

Memory-induced anomalous dynamics in a random walk model: emergence of diffusion, subdiffusion, and superdiffusion.

Date: 2011-02-25
Speaker: Dr. Niraj Kumar
Venue: Room No. 469

Abstract

A random walk model that exhibits asymptotic anomalous behavior will be presented. We will discuss how memory can influence the dynamics leading to subdiffusive, diffusive, and superdiffusive behaviors. These kinds of dynamical behaviors are well observed in real systems. Using an analytically tractable model, we will show how this diverse scenario may arise as a result of walker's response to its memory. This seems to be the first random walk model that encompasses all known dynamical behaviors.

Profile swapping and pinching in Bose-Fermi mixtures with two-color optical Feshbach resonances

Date: 2011-02-24
Speaker: Sandip Gautam
Venue: Room No. 469

Abstract

We examine the density profiles of the quantum degenerate Bose-Fermi mixture of $^{174}$Yb-$^{173}$Yb, experimentally observed recently, in the mean field regime. In this mixture there is a possibility of tuning the Bose-Bose and Bose-Fermi interactions simultaneously using two well separated optical Feshbach resonances, and it is a good candidate to explore phase separation in Bose-Fermi mixtures. Depending on the Bose-Bose scattering length $a_\BB$, as the Bose-Fermi interaction is tuned the density of the fermions is pinched or swapping with bosons occurs.

Electronics and Pulsed power supplies for time-of-flight mass spectrometry

Date: 2011-02-14
Speaker: S. B. Banerjee
Venue: Ground Floor Lecture Hall

Abstract

A New Cosmology for the Birth and Death of our Universe

Date: 2011-02-10
Speaker: Dr. Tom Gehrels
Venue: Room # 114, Thaltej Campus

Abstract

Single-particle measurements of black carbon aerosol in the atmosphere

Date: 2011-02-08
Speaker: David W. Fahey
Venue: Ground Floor Lecture Hall

Abstract

CONVERTING SPACE INTO TIME: HOW TO ORDER THE DISORDERED (Studies in the Effective Medium Approximation in Transport Theory)

Date: 2011-02-01
Speaker: V. M. Kenkre
Venue: Room No. 469

Abstract

Effective medium theory of transport in disordered systems, whose basis is the replacement of spatial disorder by temporal memory, is extended in several practical directions. A transformation procedure is developed to deduce, from given distribution functions characterizing the system disorder, explicit expressions for the memory functions. The extent of the agreement of effective medium theory predictions with numerically computed exact results is explored and a number of new results are discussed including emergence of a percolation threshold, of spatially long range transfer rates, size effects, and pausing time distributions in continuous time random walks corresponding to the effective medium memories.

Status of radial-velocity programs around the world and its future

Date: 2011-01-28
Speaker: Dr. Abhijit Chakraborty
Venue: Room # 114, Thaltej Campus

Abstract

Classical-Quantum relationship--a new point of view

Date: 2011-01-27
Speaker: Prof. R. K. Varma
Venue: Room No. 469

Abstract

Following Dirac's conjectural comments that a solution of the Hamilton-Jacobi equation, the principal function, represents a 'family' of solutions of a classical dynamical problem, we develop an equation which describes what we term as the "Hamilton-Jacobi flow." This evolves along the characteristics of the Hamilton-Jacobi equation. A Hilbert representation of the flow is then constructed and it is shown that it yields a generalized set of Schrodinger equations describing this flow. Paradoxically,these together represent classical dynamics while only one of them is identified as the quantum mechanical Scrodinger equation. The nature of this relationship is then discussed.

An ab initio derivation of electromagnetic fields of an accelerated charge

Date: 2011-01-20
Speaker: Dr. Ashok K. Singal
Venue: Room # 114, Thaltej Campus

Abstract

Theoretical study on the Aluminium Nuclear Magnetic Resonance spectroscopy

Date: 2011-01-20
Speaker: Chengbin Li
Venue: Room No. 469

Abstract

In my talk, I will introduce our semi-empirical molecular mechanical study on the Al Nuclear Magnetic Resonance (NMR) spectroscopy of zeolites. In this procedure, we consider classical molecular mechanics to describe the zeolite and use quantum mechanics to study the dynamics in the active Al sites. I will present our theoretical results and compare them with other available theoretical and the experimental results. I will also show that a partial identification of Al sites in the zeolite framework is possible.

Two-Craft Coulomb formation study about circular orbits and libration points

Date: 2011-01-17
Speaker: Ravi Kishore Inampudi
Venue: Ground Floor Lecture Hall

Abstract

Characterization and estimates of emissions from biomass burning sources

Date: 2011-01-10
Speaker: Lokesh Sahu
Venue: Ground Floor Lecture Hall

Abstract

Computational and Numerical Algebraic Geometry and Their Applications in Theoretical Physics

Date: 2011-01-06
Speaker: Dhagash Mehta
Venue: Room No. 469

Abstract

Nonlinear equations arise in theoretical physics naturally and frequently. In general, it is always difficult to solve (i.e., get ALL solutions, either exactly or numerically) them. However, if the non-linearity of the equations is polynomial-like, then one can use the computational and numerical algebraic geometry methods developed recently to solve the equations exactly or numerically, respectively. I will take an example of the XY model Hamiltonian, a well-known spin glass system, to illustrate how the methods can be used to get all stationary points. I will then briefly mention the other applications of these methods to many problems in theoretical physics (e.g., minimizing a classical hamiltonian) and non-linear dynamics (e.g., solving steady state equations of the neural models and models exhibiting synchronization).

Majorana fermions in condensed matter systems

Date: 2011-01-04
Speaker: Dr. Pavan Hosur
Venue: Room No. 469

Abstract

Majorana fermions, despite having been in the news for several decades, have not been observed conclusively so far. Although they were first proposed as candidates for neutrinos in high-energy physics, a rather different kind of realization of them has been discussed lately in condensed matter physics, where they can appear in certain superconductors. Most of these proposals, though, either require considerable amount of engineering or involve types of materials that have not yet been discovered. In our work, we propose a way to obtain Majorana states simply by passing a magnetic field through some superconductors, and give several real material examples. An easy route towards obtaining these superconductors is by doping insulators known as 'topological insulators', which have attracted tremendous theoretical and experimental recent attention in the condensed matter community themselves. However, we derive more general criterion which will allow even non-topological insulator-based superconductors to give rise to Majorana states. Additionally, the phase transition between phases with and without Majorana modes takes place through a vortex in the superconductor, which to our knowledge, is the first example of a phase transition inside a topological defect.

Effects of regional pollution and long range transport on the distribution of ozone over Ahmedabad

Date: 2011-01-03
Speaker: Shuchita Srivastava
Venue: Ground Floor Lecture Hall

Abstract

2010

Gravity wave and tidal activities in low latitude middle and lower atmosphere

Date: 2010-12-20
Speaker: Amitava Guharay
Venue: Ground Floor Lecture Hall

Abstract

Gravity waves in Mesosphere - Recent results

Date: 2010-12-13
Speaker: Sumanta Sarkhel
Venue: Ground Floor Lecture Hall

Abstract

Byzantine Astronomy From A.D. 1300

Date: 2010-12-10
Speaker: Prof. Emmanuel A. Paschos
Venue: Room No. 469

Abstract

A Byzantine article from the 13th century contains advanced astronomical ideas and pre-Copernican diagrams. The models are geocentric but contain improvements on the trajectories of the Moon and Mercury. This talk presents several models and compares them briefly with the Astronomy of Ptolemy, Arabic Astronomies of that time and the heliocentric system.

Implications of CP violating 2HDM in B Physics

Date: 2010-12-09
Speaker: Bhavik Kodrani
Venue: Room No. 469

Abstract

New sources of CP violation can arise in general two Higgs doublet models in three ways. (1) From the mixing between scalar and pseudo-scalar. (2) From the phases in couplings of tree level flavour changing neutral currents. (3) From the phases in charged Higgs couplings to the fermions. Consequences of all these CP violating effects in the general 2HDM in B systems will be discussed. In particular, we will discuss the possibility of explaining the large CP violating phase observed in Bs mixing in 2HDM.

ENWi - Concept to realization

Date: 2010-12-06
Speaker: R. Sridharan
Venue: Ground Floor Lecture Hall

Abstract

Dark Matter

Date: 2010-12-02
Speaker: Prof. Subhendra Mohanty
Venue: Room No. 469

Abstract

I will give a summary of the status of dark matter detection by direct scattering in terrestrial experiments and evidence for dark matter from cosmic ray observations.

Multi-technique investigations of Equatorial and Low Latitude Ionosphere

Date: 2010-11-29
Speaker: K.N. Iyer
Venue: Ground Floor Lecture Hall

Abstract

Beyond the Standard Model physics and it's cosmological consequences.

Date: 2010-11-25
Speaker: Sudhanwa Patra
Venue: Room No. 469

Abstract

In spite of remarkable success of Standard Model in describing the low-energy phenomena, there are many motivations to study BEYOND STANDARD MODEL(BSM) Physics. I will discuss Supersymmetric Left-Right Theory and SU(5) Guts as the BSM physics in the context of RG running, neutrino mass and Spontaneous Parity Violation. As a consequences of BSM physics, I will talk about electromagnetic leptogenesis as a way to explain the origin of baryon asymmetry of the present Universe. Instead of standard scenario of Leptogenesis, there is a different kind of leptogenesis is possible via the out of equilibrium decay of heavy right handed Majorana neutrino through 5D and 6D-EMDM couplings: i.e, NR−>νγ and NR−>νγϕ. Also resonant electromagnetic leptogenesis(at the TeV scale) and its connection to neutrino mass will be discussed.

CCD vs. CMOS

Date: 2010-11-22
Speaker: Gaurav Hirani
Venue: Ground Floor Lecture Hall

Abstract

Emergent gravity and matrix models

Date: 2010-11-19
Speaker: Prof. M. Sivakumar
Venue: Room No. 469

Abstract

Light neutrinos from massless texture and below TeV seesaw scale

Date: 2010-11-18
Speaker: Prof. Amitava Raychaudhuri
Venue: Room No. 469

Abstract

If there is new physics around the TeV scale the Type I seesaw mechanism for small neutrino mass requires fine-tuned cancellation among different contributions to the neutrino mass matrix. We generalize the possible structures of the 6 x 6 neutrino mass matrix for which neutrinos are massless in the tree approximation and such cancellations are possible. We discuss the possible symmetries for such structures of the mass matrix. Finally, we illustrate how symmetry breaking and loop corrections may lead to small neutrino masses. A seesaw scale below TeV for right-handed Majorana neutrinos might thus be admissible.

Pancharatnam, Bargmann and Berry Phases - a Retrospective

Date: 2010-10-28
Speaker: Prof. N. Mukunda
Venue: Room No. 469

Abstract

The work of Pancharatnam in classical polarisation optics, of Wigner and Bargmann on the representation of symmetry operations in quantum mechanics, and of Berry in adiabatic cyclic quantum evolution, will be described from a historical perspective. The interconnections among the three sets of ideas will be highlighted. Later important developments, including contributions from India, will be outlined.

Non linear properties of E region plasma structures: Observations and theory

Date: 2010-10-18
Speaker: Jean-Pierre St.-Maurice

Abstract

Bose Einstein Condensation: A Quantum many-body approach

Date: 2010-09-23
Speaker: Dr. Barnali Chakrabarti
Venue: Room No. 469

Abstract

The discovery of Bose-Einstein condensation in cold alakali atomic vapors and subsequent experiments including the strong interaction regimes is one of the most successful and interesting research area since last decade. A lot of theoretical works are going on in different directions to explain experimental results and predict new ones. The widely used approach is the mean field Gross-Pitavskii equation. Although it is a very convenient approach to predict gross property of the condensate, still the uncorrelated mean field equation using just contact delta interaction ( with a singularity in the origin in 3D) is questionable and deserves full quantum many body calculation using interatomic correlations and realistic interaction. Very recently, we have applied a very convenient ab-initio many body approach with certain approximation, which include two body correlations and realistic van del Walls interaction. We correctly describe ground state properties, collective excitations and also thermodynamic properties of dilute BEC in JILA trap and it can handle quite large number (approx. 15000) of bosons. Our approach has also been spectacularly successful in reproducing the controlled collapse experiment of attractive BEC in JILA trap and calculated stability factor which is in nice agreement with experiment.

The magic of earth matter effects in neutrino propgation

Date: 2010-09-16
Speaker: Dr. Srubabati Goswami
Venue: Room No. 469

Abstract

In this talk I will consider propagation of neutrinos through earth's matter and will explain some salient features of this. Specifically I will discuss the baseline 7500 km which is known as the magic baseline. I will also discuss another recently proposed baseline (2540km) which is called the bi-magic baseline. I will show the constraints that can be obtained on neutrino oscillation parameters with a 2540 km neutrino factory experiment.

Quantum dynamics of excitation energy transfer in photosynthesis: Master equation approach.

Date: 2010-09-09
Speaker: Dr. Navinder Singh
Venue: Room No. 469

Abstract

We show that the exciton motion in excitation energy transfer (EET) in photosynthesis involves non-Markovian effects and the Markovian Redfield theory cannot explain the observed coherence effects in EET. In the literature people have wrongly made the Markovian approximation in the parameter regime, in which the quantum dynamics is highly non-Markovian. The approach used here is standard one: time evolution equation for the reduced density matrix (Projection operators and quantum master equations). We have made use of the 2nd Born quantum master equation (time convolution form) and able to integrate (both in energy and site representation) this integro-differential equation with auxiliary function method. We are able to know precisely upto what value of re-organization energy and the decay rate of the phonon auto-correlation function, one can use the Markovian Redfield theory and second order approximation. We have also investigated the presence of initial coherences as the laser pulse not only excites the populations but also the coherences, this has not been taken into account in previous investigations.

Type-I seesaw mechanism for quasi-degenerate neutrinos & its SO(10) unified description.

Date: 2010-08-26
Speaker: Mr. Ketan Patel
Venue: Room No. 469

Abstract

All neutrinos being quasi-degenerate is still an allowed possibility. It is non-trivial to accommodate such possibility within the conventional pictures of neutrino mass generation. I will discuss symmetries and scenarios leading to quasi-degenerate neutrinos in type-I seesaw models. Implementation of such scheme in SO(10) based models and its consequences will also be discussed.

Chiral symmetry breaking in strong magnetic background.

Date: 2010-08-21
Speaker: Bhaswar Chaterjee
Venue: Room No. 469

Abstract

Extreme Events on Complex Networks.

Date: 2010-08-05
Speaker: Mr. Vimal Kishore
Venue: Room No. 469

Abstract

Extreme events occur rarely in nature. They have great importance due to their large socio-economic impact on the society. In this talk, we will focus on extreme events taking place on complex networks. Traffic jams, internet slowdowns, floods in river network are few examples of such events on networks. We study simple random walk model on scale-free network and show that extreme events are more likely to occur on nodes with lower degree in comparison to higher degrees nodes. This result can be useful in designing the transport networks which can handle such extreme events.

Unstable molecular ions: Experimental and Theoretical Investigation

Date: 2010-08-02
Speaker: Amrendra Pandey
Venue: Ground Floor Lecture Hall

Abstract

Thermal photons in QGP and non-ideal effects.

Date: 2010-07-20
Speaker: V. Sreekanth
Venue: Room No. 469

Abstract

We study the effect of non-ideal equation of state (EoS) and bulk viscosity on the thermal photon signals produced from the Quark Gluon Plasma produced during the relativistic heavy ion collisions. We use one dimensional boost-invariant second order relativistic hydrodynamics to find proper time evolution of the energy density and the temperature.The effect of bulk viscosity and non-ideal equation of state are taken into account in a manner consistent with recent lattice QCD estimates. We observe that the expanding plasma with a non-ideal EoS- which is important near the phase-transition point, can significantly slow down the hydrodynamic expansion and thereby increase the photon production-rates. We also analyze the interesting phenomenon of bulk viscosity induced cavitation making the hydrodynamical description invalid. It is shown that ignoring the cavitiation phenomenon can lead to a very significant overestimation of the photon flux. It is argued that this feature could be relevant in studying signature of cavitation in relativistic heavy ion collisions.

Fragmentation dynamics of molecules: Probing deeper

Date: 2010-07-19
Speaker: Kaushik Saha
Venue: Ground Floor Lecture Hall

Abstract

Desynchronization bifurcation of coupled nonlinear dynamical systems.

Date: 2010-07-19
Speaker: Suman Acharaya
Venue: Room No. 469

Abstract

We analyse the desynchronization bifurcation in the coupled chaotic systems with the specific example of coupled R矣ssler systems. After the desynchronization bifurcation the attractors of the coupled systems split into two and start moving away from each other with a square root dependence on the parameter. We define system transverse Lyapunov exponents and in the desynchronized state one of them is positive while the other is negative. This means that the attractor of one system is trying to fly away while that of the other system is holding it. We give a simple model of coupled integrable systems which shows a similar phenomena. This model can be treated as a normal form for the desynchronization bufurcation. We conclude that the desynchronization bifurcation is a pitchfork bifurcation of the transverse manifold.

Optical Vortices - Study of Coherence.

Date: 2010-07-16
Speaker: Ashok Kumar
Venue: Room No. 469

Abstract

Vortices are ubiquitous in nature; therefore exploring their properties carries a lot of significance to many branches of physics. We, on our part, have embarked on the study of the coherence properties of vortices in light known as optical vortices. These are the light beams with helical wavefront and phase singularities in the optical field. In the present talk, I will discuss field and intensity correlation properties of optical vortices. We will see that the second order coherence i.e. intensity correlation of vortices scattered by a rotating ground glass decays faster than that of a Gaussian laser beam. We observe a linear relationship in correlation time and order of the vortex.

Non-Gaussianity as a signature of thermal initial condition of inflation.

Date: 2010-07-15
Speaker: Suratna Das
Venue: Room No. 469

Abstract

Primordial non-Gaussianity is an unique feature of the CMBR, measuring which one can distinguish between the existing inflationary models. I will discuss in this presentation the effects of a pre-inflationary radiation era on primordial non-Gaussianities. We found in our work that presence of such a radiation era enhances the fNL and τNL by a considerable amount and yields large enough primordial non-Gaussianities that can be measured by future experiments like PLANCK. I will also discuss the methodology to calculate non-Gaussinities in such a scenario and the results thus obtained.

Dark Energy: constant or time variable?

Date: 2010-07-14
Speaker: Prof. Bharat Ratra
Venue: Room No. 469

Abstract

Experiments and observations over the last decade have persuaded cosmologists that (as yet undetected) dark energy is by far the main component of the energy budget of the universe. I review a few simple dark energy models and compare their predictions to observational data, to derive dark energy model-parameter constraints and to test consistency of different data sets. I conclude with a list of open cosmological questions.

SUSY Dark Matter in the light of cosmic ray experiments.

Date: 2010-07-13
Speaker: Soumya Rao
Venue: Room no. 469

Abstract

We study a supersymmetric model for Dark Matter (DM) which explains the PAMELA positron and antiproton fluxes. We consider Sommerfeld enhancement to be the source for the boost factor required in the cross section to explain the PAMELA result. We also consider the possibility of obtaining the correct relic density using a Sommerfeld enhancement factor, thus having a consistent theory which obeys constraints from relic density as well as indirect detection of DM.

Coupling processes in the equatorial ionospheric plasma bubble/spread F

Date: 2010-07-01
Speaker: M.A. Abdu
Venue: Ground Floor Lecture Hall

Abstract

Role of sulfur containing gases in the atmosphere

Date: 2010-06-28
Speaker: Chinmay Mallik
Venue: Ground Floor Lecture Hall

Abstract

Probing anomalous VZH interactions at ILC with polarized beams.

Date: 2010-06-25
Speaker: Pankaj Sharma
Venue: Room No. 469

Abstract

In this talk, I will talk about how International Linear Collider (ILC) can be utilized to its full potential using polarization (longitudinal or transverse) of both electron and positron beams, which are expected to be available at the ILC, to probe anomalous VZH couplings, where V is electroweak neutral gauge bosons i.e., Z or photon, in the process e+ e- --> HZ. I will discuss the sensitivity of simple observables like forward backward asymmetry, azimuthal asymmetries and cross sections to these anomalous couplings using various combinations of beam polarizations.

Modeling of optical and radiative properties of aerosols: State of mixing

Date: 2010-06-21
Speaker: Rohit Srivastava
Venue: Ground Floor Lecture Hall

Abstract

Aerosol radiative forcing over an urban location: Observation and Model estimates

Date: 2010-06-14
Speaker: Rohit Srivastava
Venue: Ground Floor Lecture Hall

Abstract

Regional and seasonal differences in aerosol radiative forcing over India and adjoining oceanic regions

Date: 2010-05-17
Speaker: Sumita Kedia
Venue: Ground Floor Lecture Hall

Abstract

Electrostatic Energy Analysers

Date: 2010-04-26
Speaker: N. Saneesh and Lisha Raghavan
Venue: Ground Floor Lecture Hall

Abstract

Condensation temperature of bosons for the quartic confining potential and ground state geometry of binary condensates.

Date: 2010-04-13
Speaker: Prof. S. Gautam
Venue: Room No. 469

Abstract

We calculate the critical temperature $T_c$ of non-interacting bosons, including the effect of finite boson number, at which normal to BEC transition occurs for the quartic confining potential. For two species BECs (TBECs), we show that the ground state interface geometry in the phase separated regime undergoes a smooth transition from planar to ellipsoidal to cylindrical geometry. This occurs for condensates with repulsive interactions as the trapping potential is changed from prolate to oblate. The correct ground state geometry emerges when the interface energy is included in the energy minimization, whereas energy minimization based on Thomas-Fermi approximation gives incorrect geometry. We also examine WKB approximation to calculate $p$-wave scattering length which describes the low energy scattering properties of identical fermions.

Photons, Photoionization, and Photoelectrons

Date: 2010-04-12
Speaker: K.P. Subramanian
Venue: Ground Floor Lecture Hall

Abstract

Chip-based sources of entangled photons from a single quantum dot.

Date: 2010-04-01
Speaker: Dr. Pradyumna Pathak
Venue: Room No. 469

Abstract

A source of polarization-entangled photon pairs has wide uses in quantum optics, leading to applications such as quantum computation, quantum information processing, quantum cryptography, and quantum metrology. There has been considerable progress for developing scalable sources of entangled photons using single quantum dots. In semiconductor quantum dots, entangled photons are typically generated in a biexciton-exciton cascade decay. However, the entanglement between the generated photons is limited by inherent cylindrical asymmetries and various dephasing processes. The cylindrical asymmetries produce fine structure splitting (FSS) in the exciton states; as a result, the emitted x-polarized and y-polarized photon pairs become distinguishable in frequency, and the entanglement between the photons is largely destroyed. In this talk, I will discuss "within generation" and "across generation" of entangled photons when a quantum dot is coupled in a photonic crystal cavity. I will also show that the entanglement can be distilled in both cases using a simple spectral filter.

Diffuse UHE Neutrino Fluxes and Physics beyond the Standard Model

Date: 2010-03-31
Speaker: Prof. Raj Gandhi
Venue: Room No. 469

Abstract

We study spectral distortions of diffuse ultra-high energy (UHE) neutrino flavour fluxes resulting due to physics beyond the Standard Model (SM). Even large spectral differences between flavours at the source are massaged into a common shape at earth by SM oscillations, thus, any significant observed spectral differences are an indicator of new physics present in the oscillation probability during propagation. Lorentz symmetry violation (LV) and Neutrino decay are examples, and result in significant distortion of the fluxes and the well-known bounds on them, which may allow UHE detectors to probe LV parameters, lifetimes and the mass hierarchy over a broad range.

Responses of low latitude ionosphere-thermosphere system to geomagnetic storms and substorms

Date: 2010-03-29
Speaker: D. Chakrabarty
Venue: Ground Floor Lecture Hall

Abstract

Higher Dimensional Effect on a Torsion Balance.

Date: 2010-03-25
Speaker: Dr. M. Azam
Venue: Room No. 469

Abstract

High resolution time-of-flight mass spectrometry: Design considerations and applications

Date: 2010-03-22
Speaker: Bhas Bapat
Venue: Ground Floor Lecture Hall

Abstract

Characteristics of atmospheric waves in the middle atmosphere

Date: 2010-03-16
Speaker: Amitava Guharay
Venue: Ground Floor Lecture Hall

Abstract

Trends in microelectronics

Date: 2010-03-15
Speaker: Y.B. Acharya
Venue: Ground Floor Lecture Hall

Abstract

Dark Matter in SUGRA Models with Universal and Nonuniversal Gaugino Masses.

Date: 2010-03-15
Speaker: Prof. D. P. Roy
Venue: Room No. 469

Abstract

Networks and Emergence.

Date: 2010-03-08
Speaker: Soumen Roy
Venue: Room No. 469

Abstract

Networks are used to model a wide range of complex systems. Especially, their paramount importance in the emergent field of Systems Biology is now universally accepted. We outline systematic methods to show how and why multiple network metrics should be studied in parallel. Specifically, we uncover connections between phenotypes of various biological organisms and their network architecture. We also present new models and mechanisms of network growth and demonstrate how they shed insight in analyzing and modeling various systems.

Wavelet analysis of Nonlinear oscillations.

Date: 2010-03-04
Speaker: A. N. Sekar Iyengar
Venue: Room No. 469

Abstract

Fourier analysis is very popular technique to which everyone resorts to in the analysis of fluctuations/oscillations: fluids, plasmas, finance, EEG,ECG, earthquakes etc. But the disadvantage of this technique does not yield time information which is overcome by wavelet analysis. Wavelet transforms have become quite popular in different fields of research from which one can derive both time-scale(or inversely frequency) information. We shall show how we have been able to derive information regarding presence of nonlinerity as well as the chaoticity of the system through some data obtained from our plasma experiments and from foreign exchange rates.

The Top Way to the Bottom of Things.

Date: 2010-03-02
Speaker: Prof. Debajyoti Chaudhuri
Venue: Room No. 469

Abstract

With the first papers from the LHC being published, it is imperative that we examine what we know of fundamental physics and what future experiments (primarily those at the LHC) can tell us about. In this talk, I argue that the study of the Top quark can potentially reveal much, mentioning alongside what all we still do notknow.

Exotic Nuclei: Large-scale shell model calculations.

Date: 2010-02-18
Speaker: Dr. Praveen C Srivastav
Venue: Room No. 469

Abstract

The neutron-rich nuclei in the fp and fpg shell region (Fe to Zn nuclei) are at the focus of attention of nuclear physics community at present-- thanks to Radioactive Ion Beam facilities for exploring this region widely. Unstable nuclei in this region exhibit many new phenomena such as melting of existing magic numbers and appearance of new ones, softening of core at N=28, interplay of collective and single particle properties etc. In this seminar, I am going to present our results of modern large scale shell model calculations for these two regions.

A Leptophilic Model Explaining Neutrino Masses and Dark Matter.

Date: 2010-02-16
Speaker: Dr. Michael A Schmidt
Venue: Room No. 469

Abstract

Despite all its triumphs, the Standard Model (SM) of elementary particles fails to explain two recent discoveries: dark matter and tiny but nonzero neutrino masses. In this talk, I will propose a possible connection between neutrino masses and dark matter in an economic extension of the SM and discuss its phenomenological implications. Besides constraints from dark matter search experiments, bounds from lepton flavour violation and electroweak precision measurements are outlined.

Modern Shell Model.

Date: 2010-02-04
Speaker: Prof. V. K. B. Kota
Venue: Room No. 469

Abstract

Progress in the last four decades in developing shell model codes starting from the codes for p-shell nuclei with matrix dimensions ~10-20 to the pf-shell and beyond with dimensions ~ 100 million or more and the ingredients needed for a successful shell model calculation will be discussed.

Some results using simple coupled maps

Date: 2010-01-21
Speaker: Some results using simple coupled maps
Venue: Room No. 469

Abstract

In this seminar we discuss three results dealing with some simple nonlinear coupled maps. First, we show that that the stationary density of the coupled tent map has a fractal character. Then we introduce a new method suited for the global analysis of synchronization in a coupled nonlinear system. We demonstrate it using coupled tent maps. Finally, we study coupled logistic maps whose coupling strengths change according to a learning rule. We study the effect of this learning on the network topology. This result has relevance to Neuroscience.

Global Warming Potentials to Molecular Complexes in Space

Date: 2010-01-11
Speaker: Partha Bera
Venue: Ground Floor Lecture Hall

Abstract

Advances in studying the optical properties of complex aerosols

Date: 2010-01-07
Speaker: Yinon Rudich
Venue: Ground Floor Lecture Hall

Abstract

2009

Quantum Statistics of Light From Optical Parametric Oscillators

Date: 2009-12-10
Speaker: Prof. Surendra P. Singh
Venue: Room No.469

Abstract

Study of cold and dense neutron star matter

Date: 2009-12-03
Speaker: Dr. Debarati Chatterjee
Venue: Room No. 469

Abstract

Neutron stars are unique astrophysical laboratories to study cold and dense matter under extreme conditions. It is been suggested that strange matter such as hyperons, kaons or even deconfined quarks can appear at the high densities prevailing in the neutron star core. When a neutron star is perturbed, it can be set into non-radial oscillations, emitting gravitational waves at characteristic frequencies of its quasi-normal modes. The pulsation modes are classified according to the different restoring forces, such as Coriolis restored r-modes. R-modes are unstable to gravitational radiation reaction driven instability in rapidly rotating neutron stars. The detection of gravitational waves emitted by an oscillating star may soon become possible with the upcoming generation of gravitational wave detectors. It is conjectured that r-mode oscillations could be effectively suppressed by bulk viscosity due to non-leptonic weak processes involving exotic matter in the neutron star interior. We used relativistic field theoretical models to construct the equations of state and calculated the coefficient of bulk viscosity due to non-leptonic weak interactions involving various compositions of strange neutron star matter. The influence of exotic particles and their associated bulk viscosity on the gravitational radiation reaction driven instability in the r-modes was investigated. Another pulsation mode is the pure space-time mode known as w-mode. Axial w-modes carry information on both the structure of the neutron star matter and the nature of hadronic interactions. We studied the problem of extracting information about the composition and equation of state (EoS) of the neutron star interior using axial w-modes, whose frequency and damping time can be extracted from the observation of gravitational waves.

Generation of high-power, continuous-wave, optical radiation from visible to near-infrared

Date: 2009-08-20
Speaker: Goutam K. Samanta
Venue: Room No. 469

Abstract

Although lasers have been in use for nearly 50 years, unavailability of the suitable laser gain materials precluded the development laser systems that can cover many regions of the optical spectrum, from ultraviolet (UV) and visibl to the near and mid-infrared wavelength range, with potential applications in the fields such as spectroscopy, remote sensing, trace gas detection, and many more. On the other hand, nonlinear optics has evolved as a powerful technique to generate tunable optical radiation inaccessible to ordinary lasers. Based on nonlinear effect, the optical parametric oscillators (OPOs) has become a standard device to convert a fixed laser wavelength to wide band of coherent radiation ranging from visible to far-IR. Development of continuous-wave (cw) OPOs in singly-resonant oscillator (SRO) configurations, the focus of this talk, is challenging due to the high threshold pump power (several watts). In addition, with visible pumping, photorefractive effect and thermal lensing effects become important issues to overcome. Therefore, the realization of practical cw SROs requires optimal cavity design, suitable nonlinear materials, and high-power laser with high spectral and spatial quality. In this talk, I will describe the development of advanced SRO systems based on the latest generation of quasi-phase-matched nonlinear materials, which are capable of providing cw, single-frequency radiation at unprecedented power levels exceeding 1 W and broad spectral coverage in the visible and near-infrared wavelength regions. The talk will also include some background on the origin of nonlinear optical effects, crystal optics, phase-matching and applications of OPO sources. visible to near-infrared