25-04-2006 At 04:00:00 PM
Speaker: Prof. Sayan Kar, IIT Kharagpur
Category: Seminar of General Interest
Venue: Lecture Hall
27-04-2006 At 04:00:00 PM
Speaker: Dr. Rajarshi Ray SINP, Kolkata
Category: Seminar of General Interest
Venue: Lecture Hall
We discuss a Polyakov loop enhanced NJL model to describe the QCD phase transition. Linear and nonlinear susceptibilities, specific heat, speed of sound etc. have been obtained and compared to those obtained through Lattice regularization.
09-05-2006 At 04:00:00 PM
Speaker: Dr.P.K. Mohanty,SINP, Kolkata
Category: TPSC Seminar
Venue: Lecture Hall
Non-equilibrium systems are less understood compared to their equilibriumcounter-parts. I will introduce a simple non equilibrium model which isexactly solvable and explain it's application to Celebrity Markets(crickets performance), Biological systems, Generic rules fornon-equilibrium transitions, Anomalous diffusion etc.
12-05-2006 At 04:00:00 PM
Speaker: Prof. N.Deo, Delhi University,
Category: Seminar of General Interest
Venue: Lecture Hall
The volatility of an Indian stock market is examined in terms of aspects like participation, synchronization of stocks and quantification of volatility using the random matrix approach. Volatility pattern of the market is found using the Bombay Stock Index for the three-year period 00-2002$. Random matrix analysis is carried out using daily returns of $ stocks for several time windows of $ days in 01$ to (i) do a brief comparative analysis with statistics of eigenvalues and eigenvectors of the matrix C of correlations between price fluctuations, in time regimes of different volatilities. While a bulk of eigenvalues falls within Random Matrix Theory bounds in all the time periods, we see that the largest (deviating) eigenvalue correlates well with the volatility of the index (ii) observe the corresponding eigenvector clearly shows a shift in the distribution of its components from volatile to less volatile periods and verifies the qualitative association between participation and volatility (iii) set up a variability index, V whose temporal evolution is found to be significantly correlated with the volatility of the overall market index.
23-05-2006 At 04:00:00 PM
Speaker: Dr. Manu Mathur, S.N. Bose (NCBS), Kolkata
Category: Seminar of General Interest
Venue: Lecture Hall
29-05-2006 At 04:00:00 PM
Speaker: Prof. Ashok Das, University of Rochester
Category: Colloquium
Venue: Lecture Hall
In this talk we will describe an interesting relation between zero temperature Feynman graphs and their finite temperature counterparts. In this process we will discover the notion of a radiative renormalization of the chemical potential.
30-05-2006 At 04:00:00 PM
Speaker: Dr. Dipak K. Goswami, Northwestern Univ., USA
Category: Seminar of General Interest
Venue: Lecture Hall
09-06-2006 At 04:00:00 PM
Speaker: Prof. C.S. Shastry, Amrita University, Coembatore
Category: Nuclear Physics Group Seminar
Venue: Library Lecture Hall
12-06-2006 At 04:00:00 PM
Speaker: Ananta Prasad Mishra
Category: Students' Review Seminar
Venue: Library Lecture Hall
22-06-2006 At 04:00:00 PM
Speaker: Sinu Mathew
Category: Experimental Condensed Matter Group Seminar
Venue: Lecture Hall
23-06-2006 At 04:00:00 PM
Speaker: Prof. Amruta Mishra, Physics Deptt., IIT, Delhi
Category: Seminar of General Interest
Venue: Lecture Hall
26-06-2006 At 04:00:00 PM
Speaker: Prof. Hiranmaya Mishra, PRL, Ahmedabad
Category: Colloquium
Venue: Lecture Hall
28-06-2006 At 04:00:00 PM
Speaker: Dr. Chitta Ranjan Das, Matscience, Chennai
Category: High Energy Group Seminar
Venue: Lecture Hall
29-06-2006 At 04:00:00 PM
Speaker: Prof. C.B. Das, BITS. Pilani
Category: Nuclear Physics Group Seminar
Venue: Lecture Hall
30-06-2006 At 04:00:00 PM
Speaker: Prof. Larisa Laperashvili, The Institute of Theoretical an
Category: High Energy Group Seminar
Venue: Lecture Hall
07-07-2006 At 03:00:00 PM
Speaker: Dr. Jhasaketan Nayak, Tokyo, Japan
Category: Experimental Condensed Matter Physics Group Seminar
Venue: Lecture Hall
With an aim to produce a low cost luminescent material suitable for white light emitting application, we attempted the enhancement of the visible luminescence from ZnO nanostructure. We synthesized various kind of Zno nanostructures and studied their photoluminescence properties. The nanometer size dot like structure showed brightest photoluminescence centered about yellow region of the visible spectrum. In order to enhance the luminescence further, we tried to co-dope the ZnO nanoparticles by Al and Li by a low cost, chemical co-precipitation method. Because of possible co-doping, the visible luminescence broadens and looks yellowish white, the luminescence intensity being comparable to the commercial yellow phosphor. The mechanism of the above yellowish white luminescence has not been understood. Preliminary characterization indicates a possible radiative transition associated with DAP recombination.
20-07-2006 At 04:00:00 PM
Speaker: Dr.V. R. R. Medicherla, TIFR, Mumbai
Category: Condensed Matter Physics (Experimental) Group Seminar
Venue: Lecture Hall
Ag-Pd bulk alloys have attracted much attention due to the unusual Core Level Shifts (CLS) observed in Ag and Pd with alloy composition. CLS of both alloy components show remarkably the same sign in contradiction to the expectations of the potential model for core electron energies [1]. CLS of both Ag and Pd are in good agreement with the complete screening calculation. Interestingly, there is a change of sign in Pd CLS whereas no such change of sign observed in Ag CLS. It is interesting to study the CLS in ordered surface alloys as peak positions and thus the CLS are better determined on ordered alloys due to the sharp core levels observed compared to the random alloys. We have prepared ordered surface alloys using e-beam technique in situ in the preparation chamber of the THE-XPS machine at HASYLAB, Hamburg, Germany. CLS were calculated from the high energy photoemission data and the degree of order and the Pd adsorption site were determined by NIXSW technique. Our results showed similar sign for both Ag and Pd CLS and surprisingly, there is no change of sign in Pd CLS with alloy composition. 1. I. A. Avrikosov et.al, Phys. Rev. Lett, 87, 176403 (2001)
23-08-2006 At 04:00:00 PM
Speaker: Prof. L. Sriramkumar HRI, Allahabad
Category: Seminar of General Interest
Venue: Lecture Hall
Inflation---a period of accelerated expansion in the early stages of the universe---is currently considered the most promising paradigm for describing the early stages of the universe. The success of the inflationary scenario rests on its ability to explain not only the homogeneity of the background, but also the characteristics of the inhomogeneities superimposed upon it. The inflationary epoch magnifies the tiny fluctuations in the quantum fields present at the beginning of the epoch into classical perturbations that leave their imprints as anisotropies in the cosmic microwave background (CMB). These anisotropies in turn act as seeds for the formation of the large-scale structure that we observe at the present time as galaxies and clusters of galaxies. With anisotropies in the CMB being measured with higher and higher precision, we are currently able to test the predictions of inflation better and better. In this talk, after introducing the motivations and essential features of inflation, I provide an overview of cosmological perturbation theory, and discuss the constraints from the most recent WMAP data on the inflationary parameters.
24-08-2006 At 04:00:00 PM
Speaker: Prof. L. Sriramkumar HRI, Allahabad
Category: HEP / Cosmology Seminar
Venue: Lecture Hall
The tremendous red-shifting of the perturbations during the inflationary epoch suggests that physics at the Planck scale may leave its imprints on the primordial spectrum and the cosmic microwave background. In the first part of the talk, I discuss the Planck scale corrections to the inflationary perturbation spectrum that arise in two different, locally Lorentz invariant, high-energy models. In the second part, I show that, given a modified spectrum, it can be reproduced with a suitably chosen squeezed state in the standard theory. I, therefore, argue that the primordial spectrum, by itself, may not be able to help us discriminate between the different Planck scale models of matter fields.
24-08-2006 At 11:00:00 AM
Speaker: Dr. J.R. David, HRI, Allahabad
Category: High Energy Informal Seminar
Venue: Lecture Hall
25-08-2006 At 04:00:00 PM
Speaker: Prof. S. Kandaswamy IUCAA, Pune
Category: Colloquium
Venue: Lecture Hall
Magnetic fields ordered on kiloparsec scales and larger are found in disk galaxies and even clusters of galaxies. How such fields arise and how they aquire such large scale coherence is still a matter of active research. Battery and dynamo mechanisms for such magnetogenesis will be discussed. The current problems with both dynamo mechanisms and seed field generation mechanisms will be highlighted.
30-08-2006 At 04:00:00 PM
Speaker: Dr. Colin Benjamin Centre de Physique Théorique , CNRS. Marseille, France
Category: Seminar of General Interest
Venue: Lecture Hall
We consider a model for a single molecule with a large frozen spin sandwiched in between two BCS superconductors at equilibrium, and show that this system has a $pi$ junction behavior at low temperature. The $pi$ shift can be reversed by varying the other parameters of the system, e.g., temperature or the position of the quantum dot level, implying a controllable $pi$ junction with novel application as a Josephson current switch. In contrast to previous works the importance of the contribution from the continuum of states above the superconducting gap is brought out. The free energy for certain configuration of parameters shows a bistable nature, which is a necessary pre-condition for achievement of a qubit.
08-09-2006 At 04:00:00 PM
Speaker: Dr. Amit K Chattopadhyay, University of Padova
Category: Seminar of General Interest
Venue: Lecture Hall
11-09-2006 At 04:00:00 PM
Speaker: Prof. Ajay Gupta, UGC-DAE Consortium for Scientific Research Indore Centre
Category: Colloquium
Venue: Lecture Hall
Atomic diffusion in amorphous and nanocrystalline alloys has been a subject of great interest, as it governs the changes in the structure of these alloys. Depth profiling using radioactive tracer or SIMS have been the most extensively used techniques for such studies. However, typical depth resolution of these techniques is a few nm, and this limits the minimum diffusion length that can be measured. It may be noted that the thermal stability of amorphous and nanocrystalline alloys is generally not very high, and therefore, diffusion annealing have to be done at relatively low temperatures (typically 400K-700K). As a result, the diffusion lengths achievable within a reasonable annealing time can be as small as a nanometer. Also, both amorphous and nanocrystalline alloys exhibit structural relaxation at still lower temperatures and a possible study of the effects of structural relaxation on atomic diffusivity would involve measurement of still smaller diffusion lengths. We have used nuclear resonance reflectivity of x-rays and neutron reflectivity from isotopic multilayers for precise measurement of self-diffusion in chemically homogeneous systems. The alternate layers have the same chemical composition and differ only in the isotopic abundance of one of the species (e.g., 57Fe). If the energy of the incident radiation is tuned to the nuclear resonance energy of 57Fe, large scattering contrast develops between layers containing natural Fe and 57Fe due to strong nuclear resonance scattering from 57Fe nuclei. This results in a Bragg peak in the reflectivity corresponding to the bilayer periodicity of the multilayer. Similar Bragg peak is observed in neutron reflectivity due to different scattering lengths for 57Fe and 56Fe. Height of this Bragg peak can be monitored to get information about the interdiffusion of 57Fe isotope across the interfaces. Results will be presented on self-diffusion of Fe in Fe-N and Fe-Zr alloys. In nanocrystalline Fe60N40, variation in diffusivity due to structural relaxation at temperatures as low as 393K could be observed. In Fe85Zr15 alloy films, neutron reflectivity measurements show that Fe diffusivity in amorphous and nanocrystalline states is very similar. It is suggested that in nanocrystalline phase atomic diffusion occurs mainly via grain-boundary regions which have structure similar to that in the parent amorphous phase. Effects of external stress on diffusivity will also be presented.
14-09-2006 At 04:00:00 PM
Speaker: Dr. B. Satpati.Paul-Drude Institute for Solid State ElectronicsBerlin, Germany
Category: Seminar of General Interest
Venue: Lecture Hall
Considerable efforts have been made to obtain high quality semiconductor heterostructures for electronic and optical applications. In the 3–5m mid wavelength infrared range (MWIR), an alternative to theHgCdTe dominating material technologies can be the InAs/GaSb superlattices(SL) and InSb quantum dots. In many cases, defects at the interfacesaffect the performance of the films in electronic and optoelectronicapplications. Thus, controlling the defect microstructure is of criticalimportance in these materials systems to realize their potential. In alarge lattice-mismatched system, it is almost impossible to suppress thegeneration of misfit dislocations until the epilayer grows to a usablethickness for device applications. In this talk we present GaSb/InAssupperlattice (SL) structures grown on GaSb (practically no latticemismatch) and GaAs (a large lattice mismatch) substrates and InSb QDstructure grown grown on GaSb substrate. Because of its extremely highspatial resolution transmission electron microscopy (TEM) is a naturaltechnique to apply to the nanometer-scale characterization of thesesemiconductor heterostructures. In particular, cross-sectionaltransmission electron microscopy is a powerful tool for investigatingnanometer-scale interface properties of semiconductor materials anddevices.
25-09-2006 At 04:00:00 PM
Speaker: Prof. G.Misra, ISI, Bangalore
Category: Colloquium
Venue: Lecture Hall
Operator theory plays an important role in theoretical physics. A brief introduction to operator theory will be given first. The notion of homogeneous operators will be introduced, their interesting properties will be discussed. Some explicit simple examples will be presented.
05-10-2006 At 04:00:00 PM
Speaker: Dr. Navinder Singh, RRI Bangalore
Category: Condensed Matter Theory Seminar
Venue: Lecture Hall
This seminar is divided into two parts, part I is concerned with the effect of dissipative coupling on Aharonov-Bohm magnetic flux induced orbital diamagnetism, and some applications of Lindblad Master equation for the problems of quantum diffusion and dissipation. Part II is concerned with Two-Temperature Model of non-equilibrium electron relaxation in nanoscale systems.
17-10-2006 At 04:00:00 PM
Speaker: Dr. Rajdeep Chatterjee, Phys. Deptt., University of Padova
Category: Nuclear Physics Group Seminar
Venue: Lecture Hall
30-10-2006 At 03:00:00 PM
Speaker: Dr. Bibhudatta Rout, Louisiana Accelerator Centre Univeristy of Louisiana at Lafayatte
Category: Seminar of General Interest
Venue: Lecture Hall
02-11-2006 At 04:00:00 PM
Speaker: Prasanta Kumar Das, Matscience, Chennai
Category: High Energy Group Seminar
Venue: Lecture Hall
Radion($phi$), the 55-component(graviscalor) of the five-dimensional Randall-Sundrum(RS) graviton is required to stabilize the size of the fifth spatial dimension. Being a lighter d.o.f (lighter than the RS spin-2 graviton), radion possesses a lot of interesting phenomenology that are worthwhile to explore. Here we make a direct collider search of radion at the Large Hadron Colliedr(LHC): $p p ightarrow phi ightarrow ZZ ightarrow l^+ l^- (l=e,mu)$, the so-called gold-platted channel. After making a detailed analysis of the signal and the background, we obtained constraints in the plane of new physics parameters radion mass $m_phi$ and radion vev $langle phi angle$. Finally, we briefly discuss other radion related studies.
15-11-2006 At 11:30:00 AM
Speaker: Prof. Ignazio Bombaci, University of Pisa, Italy
Category: Seminar of General Interest
Venue: Lecture Hall
In this talk I will discuss our present understanding of the internal structure of Neutron Stars and the intimate relation with the equation of state of dense hadronic matter. I will examine different likely types of Neutron Stars in connection with the various possible species of hadronic stellar constituents and models for their mutual interactions. Particularly, I will consider the possibility to have deconfined quark matter in the core of Neutron Stars (Hybrid Stars), or the potential existence of compact stars entirely made of strange quark matter (Strange Stars). Finally, I will discuss some possible astrophysical consequences of the quark deconfinement phase transition in Neutron Stars.
27-11-2006 At 04:15:00 PM
Speaker: Prof. P. Khare, Utkal University
Category: Nobel Lectures 2006
Venue: Lecture Hall
27-11-2006 At 03:15:00 PM
Speaker: Prof. N. Dey, Institute of Life Sciences
Category: Nobel Lectures 2006
Venue: Lecture Hall
27-11-2006 At 02:30:00 PM
Speaker: Prof. G.Chainy, Utkal University
Category: Nobel Lectures 2006
Venue: Lecture Hall
28-11-2006 At 04:00:00 PM
Speaker: Prof. Kuci-Hsien Chen, IAMs, Academia Since, Taipei, Taiwan
Category: Seminar of General Interest
Venue: Lecture Hall
06-12-2006 At 04:00:00 PM
Speaker: Dr. Chitta Ranjan Das, Matscience, Chennai
Category: High Energy Group Seminar
Venue: Lecture Hall
28-12-2006 At 04:30:00 PM
Speaker: Dr. Asmita Mukherjee, IIT, Bombay
Category: High Energy Group Seminar
Venue: Lecture Hall (Main Bldg.)