June-2017 Seminar

Date : 27-06-2017
Time : 16:00:00
Speaker : Ms. Akanksha Bhardwaj (PRL)
Area : Theoretical Physics
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.

Date : 22-06-2017
Time : 16:00:00
Speaker : Dr. Minati Biswal (Institute of Mathematical Sciences, Chennai)
Area : Theoretical Physics
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.

Date : 20-06-2017
Time : 16:00:00
Speaker : Mr. Balbeer Singh (PRL)
Area : Theoretical Physics
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.

Date : 13-06-2017
Time : 16:00:00
Speaker : Dr. Avdhesh Kumar (PRL)
Area : Theoretical Physics
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.

Date : 13-06-2017
Time : 16:00:00
Speaker : Mr. Venkatesh Chinni
Senior Research Fellow
Area : Geosciences Division
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.

Date : 12-06-2017
Time : 16:00:00
Speaker : Dr. Swastik Bhattacharya (IISER Thiruvananthapuram)
Area : Theoretical Physics
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.

Date : 08-06-2017
Time : 16:00:00
Speaker : Dr. Sabyasachi Ghosh (University Of Calcuttta)
Area : Theoretical Physics
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.

Date : 06-06-2017
Time : 16:00:00
Speaker : Ms. Niharika Sharma
Senior Research Fellow
Area : Geosciences Division
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.

Title : Astrophysical coronae: from sun to galaxy clusters

Date : 06-06-2017
Time : 16:00:00
Speaker : Dr. Prateek Sharma
Area : Udaipur Solar Observatory (USO)
Venue : USO Seminar Hall

Date : 01-06-2017
Time : 16:00:00
Speaker : Ms. Richa Arya (PRL)
Area : Theoretical Physics
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.