Theoretical Physics Seminar
Title : Neutrinos in Cosmology
Date : 01-05-2025
Time : 14:30:00
Speaker : Sanjit Kumar, NIT Jamshedpur
Area : Theoretical Physics
Venue : Room no: 469 (Main Campus)
Abstract
In this talk, we will begin by introducing the basics of neutrinos and their significant role in cosmology. We will discuss the thermodynamics of the early universe and examine the Boltzmann equation and the process of neutrino decoupling. Moving forward, we will explore the nature of dark matter and investigate whether neutrinos could serve as viable dark matter candidates. We will then review cosmological constraints on neutrino masses. Finally, we will discuss the possibility of sterile neutrinos as dark matter. Throughout the talk, we aim to highlight how neutrinos influence key processes in the early universe and their relevance in modern cosmology.
Title : Study of Neutrino Oscillation with non unitarity
Date : 06-05-2025
Time : 14:30:00
Speaker : Pathan Tamanna, National Institute of Technology Surat
Area : Theoretical Physics
Venue : Room no: 469 (Main Campus)
Abstract
In this talk we will present the neutrino oscillation probabilities in presence of a non unitary mixing matrix . We will show the oscillation probabilities both in vacuum and including matter effects, Using the expressions of probabilities derived, we will show at which energies and baselines the signature of non unitary will be significantly different from standard scenarios.
Title : Electron-phonon coupling induced topological phase transitions in an α-T3 quantum spin Hall insulator
Date : 13-05-2025
Time : 16:00:00
Speaker : Dr. Kuntal Bhattacharyya, IIT Guwahati
Area : Theoretical Physics
Venue : Room no: 469 (Main Campus)
Abstract
We study the phenomenon of topological phase transitions induced by electron-phonon (e-ph) coupling in an α-T3 quantum spin Hall insulator that presents smooth tunability between graphene (α = 0) and dice (α = 1) lattice. Upon deriving an effective electronic model under suitable transformations, we come across different regimes of α, which host distinct topological transitions solely mediated through e-ph coupling, manifesting robust support from the bulk gap closing and the relative changes in the topological invariant together with the edge state features. The critical e-ph strengths of these transitions strongly depend on α. We also observe the evidence of an emergent second-order topological insulator (SOTI) phase in our system, which is characterized by the existence of corner modes and its topological marker. Interestingly, these corner modes are wiped out beyond a critical e-ph coupling (albeit different for different α), referring to a SOTI-trivial phase transition induced by the e-ph coupling.
Title : Neutrinoless double beta decay in an realistic SU(5) Model
Date : 20-05-2025
Time : 14:30:00
Speaker : Debashis Pachhar, PRL
Area : Theoretical Physics
Venue : Room no: 469 (Main Campus)
Abstract
Baryon number (B) and lepton number (L) are accidental global symmetries of the Standard Model (SM). Any observed violation of these quantum numbers would provide unambiguous evidence for physics beyond the SM. Grand Unified Theories (GUTs) offer a well-motivated framework to study such violations. In this seminar, I will discuss the role of heavy scalar fields in mediating lepton number violation via neutrinoless double beta decay (0νββ) within the SU(5) framework. While the minimal SU(5) setup predicts extremely suppressed contributions to 0νββ due to the heavy scalar masses – as a consequence of the proton decay bound, we will show that this limitation can be circumvented by extending the model. Specifically, the introduction of a discrete ℤ3 symmetry and the inclusion of an additional 15-dimensional scalar representation allow for dominant contributions to the decay process. Such an extension not only remains consistent in yielding realistic fermion mass spectra but also leads to experimentally testable predictions in upcoming ton-scale 0νββ searches.