SEMINAR

Title : Electronic transport due to magnetic scattering mechanisms: the Memory Function Approach

Date : 23-09-2021
Time : 16:00:00
Speaker : Komal Kumari
Area : Theoretical Physics
Venue : Online --> https://bluejeans.com/116525241/1376

Abstract

I present the theoretical analysis of electronic transport in magnetic materials. In these materials the electrical resistivity originates from electron magnetic spin fluctuation scattering (alongwith electron-phonon scattering). I use the Kondo-lattice Hamiltonian to investigate the temperature dependence of resistivity in heavy fermion materials. Computations of resistivity are performed using the Memory function formalism. I also explore the behaviour of resistivity in two dimensional ferromagnets tuned near to their magnetic instability. In this case, the calculations are performed using the random phase approximation for the dynamical susceptibility, from which the resistivity is computed. Our calculations are applicable to weakly ferromagnetic systems and to heavy fermion materials.

Title : The anatomy of the multi-lepton anomalies at the LHC and a candidate for a singlet scalar

Date : 20-09-2021
Time : 14:30:00
Speaker : Prof. Bruce Mellado
Area : Theoretical Physics
Venue : Online --> https://bluejeans.com/706821627/1905

Abstract

In this presentation an account of the multi-lepton (electrons and muons) anomalies at the LHC is given. These include the excess production of opposite sign leptons with and without b-quarks, including a corner of the phase-space with a full hadronic jet veto; same sign leptons with and without b-quarks; three leptons with and without b-quarks, including also the presence of a $Z$. Excesses emerge in corners of the phase space where a range of SM processes dominate, indicating that the potential mismodeling of a particular SM process is unlikely to explain them. A procedure is implemented that avoids parameter tuning or scanning the phase-space in order to nullify potential look-else-where effects or selection biases. The internal consistency of these anomalies and their interpretation in the framework of a simplified model are presented. Motivated by the multi-lepton anomalies, a search for narrow resonances with $S\rightarrow\gamma\gamma, Z\gamma$ in association with light jets, $b$-jets or missing transverse energy is performed. The maximum local (global) significance is achieved for $m_S=151.5$\,GeV with 5.1$\sigma$ (4.8$\sigma$).

Title : New Insights into the Gully-fan Formation Processes from the Morphometric Measurements

Date : 17-09-2021
Time : 15:00:00
Speaker : Rishitosh Kumar Sinha
Area : Planetary Sciences Division
Venue : Online

Abstract

Until the past decade or so, gullies on Mars have been thought to have formed from the recent flow of ice/snow melt water. However, some of the recent studies focused on analyzing present-day activity in gullies absolutely denied the role of volatiles (both water and water-ice) for the observed changes in the gullies and rather postulated gullies to have ever formed from a dry process, i.e. by sublimation of dry carbon dioxide ice. While the gullies on Mars have formed over distinct geologic settings such as on crater walls (1) influenced by past glaciation and recent LDM (latitude dependent mantle) cover, (2) influenced by only LDM cover, and (3) without any influence of LDM and glaciation (i.e. fresh gully systems), we argue that the process related to the sublimation of dry carbon dioxide alone cannot explain the formation of the entire gully population. Instead, we suggest that the formative geomorphic processes were different and the underlying material is the culprit. The fresh gully systems typically cut into bedrock, while those with LDM and glacial typically cut in the finer-grained deposits. We suggest this based on our detailed morphologic and morphometric measurement of the gully-fan characteristics that includes estimation of parameters such as melton ratio, fan concavity, fan gradient and alcove length. These parameters were estimated for gullies formed inside 27 craters between 30-60 degrees in Mars' southern hemisphere. Furthermore, we propose that the melton ratio and fan gradient parameters statistically provide a best discrimination of the distinct gully fan types analysed in this study.

Title : Synergy of Neutrino and Dark matter at the advanced particle detector

Date : 16-09-2021
Time : 11:00:00
Speaker : Animesh Chatterjee
Area : Theoretical Physics
Venue : Online --> https://bluejeans.com/165045009/1320

Abstract

The predictions of the standard model (SM) have been verified to a remarkable degree of accuracy, but there are still some unanswered questions. Neutrino and dark matter offer great potential for digging out physics beyond the standard model. With the advent of a new generation of advanced neutrino experiments, it is timely to explore physics topics beyond the standard neutrino oscillation. Dark matter phenomenology is turning to more exotic models, neutrino detectors are sensitive to some of those. In this talk, I will discuss the opportunity to explore physics beyond the standard neutrino oscillations, as well as how one can search for dark matter using the same existing setup for neutrino experiment.

Title : Next generation 'New' Noble gas mass spectrometer for "single grain" analysis

Date : 10-09-2021
Time : 16:00:00
Speaker : Shri Ramakant R. Mahajan
Area : Planetary Sciences Division
Venue : Online

Abstract

With the discovery of neon isotopes by J. J. Thomson, isotope science came into existence. The noble gas mass spectrometry field flourished from the investigation of returned Lunar samples. New falls of meteorites provide a means of studying the oldest and pristine samples of the solar system. Subsequently, noble gas isotopic studies revealed many secrets of the solar system. e.g. It established the pre-solar origin of "pre-solar grains" from the discovery of anomalous xenon isotopes. The noble gas mass spectrometer at PRL came into established in the decade of seventies. It has gone several folds of new developments for scientific need. Many new results were published from these facilities. e.g. the 'nitrogen isotopes in chondrules' is only available from PRL-NGMS facilities. Now the time has came for next generation of noble gas mass spectrometer facility. In this talk, present status of the existing facilities and the scientific rationale for future requirement of new Noble gas mass spectrometer for single grain analysis will be discussed.

Title : Various Aspects of Modeling in Astrochemistry

Date : 03-09-2021
Time : 16:00:00
Speaker : Dr. Kinsuk Acharyya
Area : Planetary Sciences Division
Venue : Google meet

Abstract

Molecules are found in a wide variety of astronomical conditions, ranging from star-forming regions to the outer envelopes of carbon stars and from objects in our solar system to distant metal-poor galaxies. The complexity of these molecules ranges from simple diatomic molecules to amino acids such as glycine. Their association with various phases of star and planet formation are of particular interest; they can serve as building blocks of more complex molecules and can provide an insight into the primordial composition of our planet Earth, thereby addressing the issue of “how life originated on Earth”. Besides, they are useful probes of the physical conditions of their environment and related to the lifetime of the sources. Many molecules are not found in the terrestrial conditions that are of interest for what they tell about the build-up of molecular complexity throughout the Universe. Therefore, the study of the formation of these molecules is of paramount importance. In this talk, I will discuss how the formation of these molecules can be studied using numerical simulations in diverse astrophysical sources.