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

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.

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

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.

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

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.

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

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.

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

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.

Title : Understanding evolution of cometary volatiles

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.

Title : Atmospheric evaporation from exoplanets

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.

Title : Study of Neutrino Oscillation with non unitarity

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.

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

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.

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

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.

Title : Neutrinos in Cosmology

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.