PRL Theory Group

Inauguration of Vikram Discussion 2026 Neutrino Oscillation Mass and Beyond

🚩 Workshop on Condensed Matter Physics
📅 Dates: 09–13 March 2026
📍 Research Laboratory, Ahmedabad

Interested participants are invited to apply online using the application link provided on the workshop webpage https://sites.google.com/view/prlcmpworkshop/home?authuser=0

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THEORETICAL PHYSICS SEMINAR
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Date: November 28, 2025
Time: 02:30 p.m.

Venue: Room no. 469 (Theory Seminar Room)

Title: Strong CP violation in dense matter : Consequences for neutron stars

Speaker: Prof. Hiranmaya Mishra, NISER Bhubaneswar

Abstract: "We investigate the effects of including strong CP violating effects through axion fields in the microscopic equation of state of massive hybrid neutron stars. We assume that their cores contain deconfined quark matter and include the effects of axions via an effective‘t Hooft determinant interaction. The hadronic crusts are described using different approaches in order to make our results more general. We find that the presence of axions stabilizes massive hybrid neutron stars against gravitational collapse by weakening the deconfinement phase transition and bringing it to lower densities. This enables to reproduce hybrid neutron stars in agreement with modern astrophysical constraints."

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THEORETICAL PHYSICS SEMINAR
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Date: November 18, 2025
Time: 02:30 p.m.

Venue: Room no. 469 (Theory Seminar Room)

Title: Monte Carlo Sampling for Wave Functions Requiring (Anti)Symmetrization

Speaker: Dr. Ajit C. Balram, Institute of Mathematical Sciences (IMSc), Chennai

Abstract: "Many strongly correlated states, such as those arising in
the fractional quantum Hall effect and spin liquids, are described by
wave functions obtained by dividing particles into multiple clusters,
constructing a readily evaluable wave function in each cluster, and
(anti)symmetrizing across these clusters. We introduce a method to
compute quantities such as energies and correlators, using Monte Carlo
simulations for these states. Our framework overcomes the factorial
scaling of explicit (anti)symmetrization, allowing for studies of
systems beyond the reach of exact diagonalization."

🚨 JUNO results are in! 🚨

The first results from the world's largest neutrino detector have just been published, and they reveal the most precise measurements of neutrino parameters yet.

After running the detector — the Jiangmen Underground Neutrino Observatory (JUNO), in southern China — for just shy of two months, the researchers were able to measure the parameters of the different types, or "flavors," of neutrinos with unprecedented precision.

Full article link in comments 🔗

Image credit: JUNO collaboration

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THEORETICAL PHYSICS SEMINAR
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Date: November 27, 2025 (Today)
Time: 04:00 p.m.

Venue: Room no. 469 (Theory Seminar Room)

Title: Coexistence of electron and phonon topology in pyrite type semimetals

Speaker: Prof. G. S. Vaitheeswaran, University of Hyderabad

Abstract: "Over the past two decades, the pursuit of novel topological phases of matter has become a major focus in condensed matter research. Beyond Dirac and Weyl particles, a variety of unique quasiparticles, distinct from those studied in high- energy physics, have attracted significant attention. This study explores multi- fold degenerate fermions beyond Dirac and Weyl types in pyrite-structured SiX₂ compounds, where X = P or As. Through symmetry analysis, we uncover the topological features of multi-fold fermions with four-fold and six-fold degeneracies located at the Γ and R points of the Brillouin zone. These nodes, protected by crystalline symmetries, present an excellent platform for investigating novel topological properties and the physical phenomena associated with them.
Additionally, these compounds exhibit intriguing topological features in their phonon dispersions. Specifically, we identify the coexistence of three nodal surfaces (NSs) and a phononic Dirac nodal-line (DNL) network. This DNL network consists of three intersecting nodal lines, each residing in a distinct momentum plane (kx, ky, kz) and converging at a common nodal point. Such a configuration is extraordinarily rare in phononic systems, creating opportunities for experimental validation through observable phononic surface states. These findings establish SiX₂ compounds as a promising platform for studying multi-fold fermions and their potential applications. Moreover, the discovered phononic topologies highlight these materials as exceptional candidates for investigating novel bosonic excitations, advancing the understanding of topological phenomena in solid-state systems."
Ganapathy Vaitheeswaran

Talk by Safana Saji MSc student from IISER Mohali. She did her MSc dissertation at PRL Theory group with Prof. Srubabati Goswami

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THEORETICAL PHYSICS SEMINAR
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Date: November 4, 2025 (Today)
Time: 2:30 PM

Venue: Room no. 469 (Theory Seminar Room)

Title: Neutrino oscillations in the plane wave and wave packet formulations

Speaker: Safana P Shaji, IISER Mohali

Abstract: Starting with the theoretical development of neutrino oscillations from plane wave to wave packet formulation, the talk aims to provide insight into the quantity of decoherence, which outlines the wave packet separation. The comparison of oscillated and decohered events is carried out through the lens of Jiangmen Underground Neutrino Observatory (JUNO) experiment, within which we delve into the mass hierarchy and theta12 sensibilities.

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THEORETICAL PHYSICS SEMINAR
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Date: September 25, 2025
Time: 2 p.m.
Venue: Room no. 469 (Theory Seminar Room)

Title: Stable and Interpretable Jet Physics with IRC-Safe Equivariant Feature Extraction

Speaker: Deepanshu Srivastava, PRL

Abstract: Deep (machine) learning has achieved remarkable success in the complex area of QCD (Quantum Chromodynamics) jet classification using low-level calorimeter data from high-energy physics detectors. However, a significant challenge persists: understanding what these models learn and how their features correlate with established QCD observables. Improving interpretability is essential for building robust and trustworthy machine learning tools in any of their applications. To tackle this challenge, we present a case study using graph neural networks for quark–gluon discrimination, systematically incorporating physics-motivated inductive biases. In particular, we design message-passing architectures that enforce infrared and collinear (IRC) safety, as well as additional symmetries, including E(2) and O(2) equivariance in the rapidity–azimuth plane. Using simulated jet datasets, we compare these networks to unconstrained baselines in terms of classification performance, robustness to soft emissions, and internal feature organisation. Our findings demonstrate that embedding symmetry and safety constraints not only improve robustness but also ground network representations in established QCD structures, providing a principled path toward interpretable deep learning in collider physics.

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THEORETICAL PHYSICS SEMINAR
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Date: October 7, 2025
Time: 2:30 p.m.

Venue: Room no. 469 (Theory Seminar Room)

Title: Improved Constraints on Coexisting WIMP/ FIMP Dark Matter and Primordial Black Holes.

Speaker: Dr. Prolay Krishna Chanda, Tata Institute of Fundamental Research, Mumbai

Abstract: Particle dark matter and primordial black holes (PBHs) may coexist with significant cosmic abundances, each contributing to the observed dark matter density ΩDM. Large populations of PBHs with ΩPBH ∼ ΩDM are strongly constrained for masses above 10−11M⊙. If the WIMP/ FIMP particle dark matter has interactions with the Standard Model, new constraints arise due to pair-annihilations that are enhanced by the PBHs, resulting in dark matter indirect detection constraints on fPBH — these bounds rule out the mixed WIMP-PBH dark matter for velocityindependent cross-section, ⟨σv⟩ ∼ 10−26cm3/s. In this talk, we will discuss how a particle DM candidate with a velocity-dependent cross-section relaxes these bounds. We also derive the bounds on mixed scenarios in which PBHs coexist with particle dark matter whose relic abundance is set via freeze-in (‘FIMPs’). We show that while the restrictions on fPBH are less constraining for FIMPs than WIMPs, modest bounds still arise for large classes of models.

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THEORETICAL PHYSICS SEMINAR
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Date: October 10, 2025
Time: 11:00 a.m.

Venue: Room no. 469 (Theory Seminar Room)

Title: Search for dark matter over a wide mass range: using JWST and neutrino telescopes to search for non-gravitational signatures of dark matter.

Speaker: Dr. Ranjan Laha, Indian Institute of Science, Bengaluru

Abstract: I will discuss two different ways to search for dark matter (DM).

First, I will discuss how we used JWST data to probe eV-scale QCD axion DM or axion-like particle (ALP) DM decaying into two photons. This will produce a distinct line signature in the spectroscopic observations made by JWST. Using the latest NIRSpec IFU spectroscopic observations from JWST, we put some of the strongest bound on the photon coupling for QCD axion/ ALP DM in the mass range between 0.47 and 2.55 eV.
In the second part of my talk, I will discuss how neutrino telescopes like IceCube and Super-Kamiokande can probe DM - electron scattering. DM can get captured inside the Sun due to DM - electron scattering and it can annihilate into neutrinos and anti-neutrinos. Using latest neutrino measurements, we set world leading limit on DM - electron scattering for DM masses between 10 GeV to about 10^5 GeV."