April-2018 Seminar

Date : 24-04-2018
Time : 00:00:16
Speaker : Ms. Niharika Sharma
Senior Research Fellow
Area : Geosciences Division
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.

Title : Chandrayaan-2 landing site on the Moon: A remote sensing perspective

Date : 13-04-2018
Time : 15:30:00
Speaker : Mr. Rishitosh Sinha
Scientist SD
Area : Planetary Sciences Division
Venue : Room 113, Thaltej Campus

Date : 09-04-2018
Time : 16:00:00
Speaker : Bighnaraj Sarangi
Area : Space and Atmospheric Sciences Division
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.

Title : Formation of gas-phase water in the interstellar medium

Date : 09-04-2018
Time : 00:11:00
Speaker : S. Sunil Kumar
Area : Atomic, Molecular and Optical Physics
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.

Title : Mean horizontal winds for a Vortex system

Date : 06-04-2018
Time : 16:00:00
Speaker : Shefali Uttam
Senior Research Fellow
Area : Planetary Sciences Division
Venue : Room 113, Thaltej Campus

Title : Constraining black-hole spins with gravitational wave observations

Date : 06-04-2018
Time : 14:30:00
Speaker : Dr. Vaibhav Tiwari (Cardiff University, UK)
Area : Theoretical Physics
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.

Title : Quantum simulation with ultracold atoms in optical lattices

Date : 06-04-2018
Time : 00:17:00
Speaker : Dr. Bodhaditya Santra
Area : Atomic, Molecular and Optical Physics
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)

Title : Heavy quarks as probes of longitudinal structure of the fireball in relativistic heavy ion collisions

Date : 03-04-2018
Time : 16:00:00
Speaker : Dr. Sandeep Chatterjee ( AGH Univ. Of Science and Tech, Krakow)
Area : Theoretical Physics
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.