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Prof. Anandmayee Tej
Indian Institute of Space Science and Technology
Probing high-mass star formation with multi-wavelength
observations
11 April, 2014, Friday
4 pm
FB-382
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Prof. Sayan Kar
IIT Kharagpur
A century of extra dimensions
28 March, 2014, Friday
4 pm
FB-382
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Prof. Tirthankar Roy Choudhury
NCRA, Pune
Probing the Universe through Neutral Hydrogen
14 February, 2014, Friday
4 pm
FB-382
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Prof. R. P. Singh
PRL Ahmedabad
Hanbury Brown Twiss Experiment: Intensity Correlations in Scattered Optical Vortices
7 February, 2014, Friday
4 pm
FB-382
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Prof. Kaushik Bhattacharya
IIT Kanpur
Astrophysical properties of Bertrand spacetime
31 January, 2014, Friday
4 pm
FB-382
In classical mechanics Bertrand's theorem specifies the kind of potentials which can give rise to closed, stable circular orbits. One can generalize the results of Bertrand's theorem in special relativity where the particle moving in the potential can have high speeds. There has been a generalization of Bertrand's theorem in general relativity where one can have certain spacetimes called Bertrand spacetimes (BSTs). From each point on the spatial hypersurface of a BST there can pass a closed, stable circular orbit. These spacetimes can have very interesting properties as far as galactic astrophysics is concerned. The talk will focus on the astrophysical properties of BSTs and will particularly focus on the issues concerning velocity rotation curves and the dark-matter source which can seed such a spacetime.
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Prof. T. R. Seshadri
Delhi University
Learning about the Universe through the Cosmic Microwave Background Radiation
17 January, 2014, Friday
4 pm
FB-382
We are surrounded by a bath of radiation which is of primordial origin. This radiation is coming from all directions. It has a nearly blackbody spectrum with its peak at 160.2 GHz which is in the microwave region. Hence the name the Microwave Background radiation. Several physical processes during the course of the evolution of the Universe leave their imprint on this radiation in the form of anisotropy, polarization and deviation from the Planck Spectrum. This talk will focus on some of these features and what it can teach us about these physical processes. Particular focus will be on the effect of Cosmic Magnetic fields.
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Prof. Mishkatul Bhattacharya
Rochester institute of Technology, Rochester, NY USA
Chiral symmetries associated with angular momentum
10 January, 2014, Friday
4 pm
FB-382
In quantum mechanics, symmetries are usually associated with physical observables which commute with the system Hamiltonian. In this talk we will discuss chiral symmetries, which anticommute with the Hamiltonian. Typically, physics students are exposed to chiral symmetries only in advanced courses, such as when they read about the Dirac equation in relativistic quantum mechanics, or when they study particle-hole symmetry in superconductivity. In this talk, we will show that chiral symmetries can be discussed in the classroom by simply using the theory of angular momentum, which is taught in virtually all introductory quantum mechanics courses. Further, we will demonstrate that while chiral symmetries cannot be associated with conserved quantities, they nonetheless simplify, and sometimes render analytically solvable, the underlying Hamiltonian. Finally, we will present as an example our recent exact solution of the effective Hamiltonian of the
ground state of the OH molecule in combined electric and magnetic fields [1].
[1] M. Bhattacharya, Z. Howard and M. Kleinert, Phys. Rev. A 88, 012503
(2013).
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Prof. Dilip Kanhere
University of Pune
Clusters at Finite Temperature: Size sensitive melting, Influence of geometry, higher than bulk melting temperatures and glassy behavior.
15 November, 2013, Friday
4 pm
FB-382
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Prof. Uma Sankar
IIT Mumbai
Life of Nu
8 November, 2013, Friday
4 pm
FB-382
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Prof. P. Ravindran
Central University of Tamil Nadu
Application of Solar Thermal Energy - Recent Developments
1 November, 2013, Friday
4 pm
FB-382
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Prof. Sudeshna Sinha
IISER, Mohali
Dynamically Rewired Networks
18 October, 2013, Friday
4 pm
FB-382
We will first discuss broad classes of models of complex systems in general, and complex networks in particular. Then we will go on to show how spatiotemporal chaos in networks with strongly chaotic nodal dynamics can be tamed by dynamically changing links. Specifically, we will illustrate the results in examples ranging from neuronal networks to disease spreading models.
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Prof. Indra Dasgupta
Indian Association for the Cultivation of Science
First Principles Calculations: The glue that binds materials, models and mechanism.
4 October, 2013, Friday
4 pm
FB-382
First principles electronic structure calculations based on density functional theory have emerged as a successful method in understanding and predicting properties of diverse class of materials. Often such calculations provide crucial insights into novel properties of materials either by themselves or in conjunction with experiments. In the present talk, we shall illustrate the usefulness of such calculations considering several examples ranging from low dimensional quantum spin systems to nanomaterials. As a first example, we shall discuss the electronic structure of the improper multiferroic, FeTe2O5Br where ferroelectricity (FE) is induced by an inversion symmetry breaking magnetic ordering resulting in strong coupling between the two order parameters. We show that the system, FeTe2O5Br is rather unique where exchange striction in the magnetically ordered state promotes polarizable Te4+ lone pair to develop ferroelectric polarization. Next we shall explain the electronic structure of the spin gap compound Sr2Cu(BO3)2 and illustrate that a careful analysis of the electronic structure is important for the identification of the correct low energy model Hamiltonian for this system. The validity of the proposed model is checked by calculating the magnetic susceptibility as a function of temperature and magnetization both as a function of temperature as well as field using quantum Monte Carlo technique and comparing them with the available experimental data. Finally we show the importance of ligands in controlling the crystal structure of nano-systems. Recently, with the aid of careful experiments it was shown that CdS nanocrystals can be thermodynamically stabilized in both wurtzite and zinc-blende crystallographic phases at will, just by the proper choice of the capping ligands. Our theoretical calculations not only provide an understanding of the mechanism but also make predictions that can be tested by experiments.
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Prof. Mohammad Sami
JMI, New Delhi
Cosmic acceleration: dark energy and beyond.
23 August, 2013, Friday
4 pm
FB-382
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Prof. Nirmal Viswanathan
University of Hyderabad
Singular and Topological Optics
14 August, 2013, Wednesday
4 pm
FB-382
Singularities are an integral part of the physical world, from cosmology to quantum world, from fluid dynamics to optical physics. The most interesting aspect of the singularity is the universality of the topological structures which are independent of the physical system, reflecting the fact that the underlying physical phenomena are common to all branches of physics and science in general.
The topological connections in complex fields provide a quantitative understanding of how the skeleton structures are formed, connected and are related to physical quantities. Topological representation of complex tensor and vector flow fields provide a very useful visualization tool in engineering, medicine, soft active matter and in
several branches of physics. I will present our endeavor in this emerging area of optical physics, connecting the points of scalar, vector, and tensor wave fields with singular lines which includes wave dislocations, optical vortices and polarization singularities.
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Dr. Sourish Basu
SRON Netherlands Institute for Space Research, Utrecht, Netherlands
Can we detect carbon cycle anomalies from satellites?
8 August, 2013, Friday
4 pm
FB-382
To quantify the carbon cycle and estimate its climate response in the future, we need to understand its mechanisms in the present. One way to estimate the surface sources and sinks of carbon is to derive those from observed atmospheric gradients of carbon-containing gases such as CO2, CO and CH4. Those estimates are only as accurate as the density of the observing network, which is low over some of the most ecologically interesting areas of the planet. To bridge this gap, we can use satellites for observation, which come with their own challenges. I will describe how we can use satellites to quantify the carbon cycle, and show some results demonstrating the added value of satellite data over the existing surface observation network.
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Prof. Tapobrata Sarkar
IIT Kanpur
Gravitational lensing, or what General Relativity can teach us about galaxies.
2 August, 2013, Friday
4 pm
FB-382
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