Physics and Astronomy, Mathematical Physics, General Medicine
FUTURE PROJECTS
Exploring a quantum corrected gravitational collapse
Applications Invited collaborators
Thermodynamics nature of gravity
Applications Invited collaborators
37
Scopus Publications
Scopus Publications
Is phantom barrier crossing inevitable? A cosmographic analysis Nandan Roy, Soumya Chakrabarti European Physical Journal C, 2026 Recent findings from the Dark Energy Spectroscopic Instrument (DESI), when combined with supernova observations and CMB measurements, provide indications of a time-evolving dark energy component, with possible hints of phantom-like behavior in the recent past. Motivated by these developments, we investigate late-time cosmic acceleration within a cosmography-inspired framework based on the jerk parameter. Instead of adopting a phenomenological parametrization of the dark energy equation of state, we reformulate the differential equation defining the jerk into a class of integrable anharmonic oscillator equations through a specific closure ansatz. This procedure selects a restricted but analytically solvable subclass of cosmographic evolutions, leading to a closed-form expression for the dark energy equation of state governed effectively by a single parameter. Using DESI-DR2 BAO data, supernova data, and a compressed Planck likelihood, we constrain the cosmological parameters and find deviations from a cosmological constant at late times. Within this integrable model class, we do not find evidence of phantom barrier crossing. Further we show, using a dynamical systems approach, that $$w_{DE} = -1$$ w DE = - 1 corresponds to a generic bifurcation point, which prevents crossing within cosmographic framework.
Geometric selection rules for singularity formation in modified gravity Soumya Chakrabarti European Physical Journal C, 2026 We argue that the polynomial degeneracies of curvature invariants can act as geometric selection rules for spacetime singularities in modified theories of gravity. The degeneracies arise purely from the algebraic structure of Riemannian geometry and impose non-trivial constraints on the effective energy–momentum tensor. We derive these constraints for metric f ( R ) gravity and a wide class of scalar–tensor theories to show that a singularity formation is generally occluded by curvature and/or scalar-induced anisotropies. Therefore, formation of a singularity in modified theories of gravity is not always a generic outcome but can occur only along algebraically admissible branches selected by Riemannian curvature invariants.
On the stability of the objects of limiting compactness: Black hole and Buchdahl star Soumya Chakrabarti, Chiranjeeb Singha, Naresh Dadhich Physics Letters Section B Nuclear Elementary Particle and High Energy Physics, 2026 In General Relativity, there exist two objects of limiting compactness, one with a null boundary defining the horizon of a black hole and the other with a timelike boundary defining a Buchdahl star. The two are characterized by gravitational energy equal to or half the mass. Since non-gravitational mass-energy is the source of gravitational energy, these configurations suggest an underlying energetic balance. In this letter, we demonstrate, in a simple and general manner, that the corresponding equilibrium state always represents a minima of an appropriate quasi-local energy functional, thereby establishing energetic (variational) stability within the quasi-local configuration space.
On the polynomial degeneracy of Ricci invariants and spacetime singularity Soumya Chakrabarti Physics Letters Section B Nuclear Elementary Particle and High Energy Physics, 2025 We explore the connection of a general relativistic matter-energy momentum tensor with the polynomial degeneracies of curvature invariants defined in Riemannian geometry. The degeneracies enforce additional constraints on the energy-momentum tensor components. Due to these constraints the formation of a curvature singularity, for instance during a gravitational collapse can no longer be treated as inevitable. We find that there can be a formation of singularity iff the interior fluid evolves into ( i ) a pressure-less dust, ( i i ) an isotropic sphere or ( i i i ) a distribution with negative pressure.
The CosmoVerse White Paper: Addressing observational tensions in cosmology with systematics and fundamental physics Eleonora Di Valentino, Jackson Levi Said, Adam Riess, Agnieszka Pollo, Vivian Poulin, et al. Physics of the Dark Universe, 2025 The standard model of cosmology has provided a good phenomenological description of a wide range of observations both at astrophysical and cosmological scales for several decades. This concordance model is constructed by a universal cosmological constant and supported by a matter sector described by the standard model of particle physics and a cold dark matter contribution, as well as very early-time inflationary physics, and underpinned by gravitation through general relativity. There have always been open questions about the soundness of the foundations of the standard model. However, recent years have shown that there may also be questions from the observational sector with the emergence of differences between certain cosmological probes. In this White Paper, we identify the key objectives that need to be addressed over the coming decade together with the core science projects that aim to meet these challenges. These discordances primarily rest on the divergence in the measurement of core cosmological parameters with varying levels of statistical confidence. These possible statistical tensions may be partially accounted for by systematics in various measurements or cosmological probes but there is also a growing indication of potential new physics beyond the standard model. After reviewing the principal probes used in the measurement of cosmological parameters, as well as potential systematics, we discuss the most promising array of potential new physics that may be observable in upcoming surveys. We also discuss the growing set of novel data analysis approaches that go beyond traditional methods to test physical models. These new methods will become increasingly important in the coming years as the volume of survey data continues to increase, and as the degeneracy between predictions of different physical models grows. There are several perspectives on the divergences between the values of cosmological parameters, such as the model-independent probes in the late Universe and model-dependent measurements in the early Universe, which we cover at length. The White Paper closes with a number of recommendations for the community to focus on for the upcoming decade of observational cosmology, statistical data analysis, and fundamental physics developments. Download: Download high-res image (270KB) Download: Download full-size image
Traversable Wormholes with a Spontaneous Symmetry Breaking Scalar Field Soumya Chakrabarti, Chiranjeeb Singha Fortschritte Der Physik, 2025 The authors argue that a spherically symmetric traversable wormhole solution of the Einstein field equations can be supported by minimally coupled self‐interacting scalar field, which allows a spontaneous symmetry breaking of the field around the wormhole throat. Two cases are studied by the authors: (i) the phantom wormhole solution of Bronnikov and (ii) a generalized Kiselev wormhole. The property of radial null geodesics is studied by authors and the metric can describe either a two‐way or a one‐way traversable wormhole depending on certain parameter ranges are showed. The scalar field exhibits spontaneous symmetry breaking (SSB) within the coordinate range where a wormhole throat forms and helps one suggest that SSB may act as a threshold for wormhole throat formation. The authors also computed the radius of the photon sphere, the Lyapunov exponent, the shadow radius, and the innermost stable circular orbits for the geometries.
Acceleration from a phase of entropic balance Soumya Chakrabarti European Physical Journal C, 2025 We discuss the notion of generating a cosmic inflation without any big bang singularity. It has recently been proved by Good and Linder (arXiv:2503.02380 [gr-qc]) that such an expansion of the universe can be driven by quantum fluctuations embedded in vacuum. The rate of expansion is guided by a cosmological sum rule defined through the Schwarzian derivative. We explore the thermodynamic roots of Schwarzian and connect it with the surface gravity associated with an apparent horizon. In General Relativity the cosmological sum rule can be enforced only if the early universe is a Milne vacuum. We show that this restriction can be removed by considering an entropic source term in the Einstein–Hilbert action.
A cosmological reconstruction of the Higgs vacuum expectation value Soumya Chakrabarti, V. Anagha, Selva Ganesh, Vivek Menon European Physical Journal C, 2024 We present a simple toy model of cosmic acceleration driven purely by a self-interacting scalar field embedded in theory of grand unification. The scalar self-interaction is Higgs-like and provokes a spontaneous symmetry breaking. The coefficient of the quadratic term in the self-interaction potential has an evolution and it leads to a cosmic variation of proton-to-electron mass ratio, $$\\mu $$ μ . We perform a cosmological reconstruction from the kinematic parameter jerk and discuss a few cosmological consequences of the theory. We also compare the theoretically calculated $$\\mu $$ μ variation with the observations of molecular absorption spectra from Cesium Atomic Clock data.
Phase Transition and Thermodynamic Stability in an Entropy-Driven Universe Soumya Chakrabarti Fortschritte Der Physik, 2024 Motivated by the notion that the mathematics of gravity can be reproduced from a statistical requirement of maximal entropy, the consequences of introducing an entropic source term in the Einstein–Hilbert action are studied. For a spatially homogeneous cosmological system driven by this entropic source and enveloped by a time‐evolving apparent horizon, a modified version of the second law of thermodynamics is formulated. An explicit differential equation governing the internal entropy profile is found. Using a Hessian matrix analysis of the internal entropy, the author checked the thermodynamic stability for three categorically different toy models describing (i) a cosmology, (ii) a unified cosmic expanson, and (iii) a non‐singular ekpyrotic bounce. The mathematical condition for a second order phase transition during these evolutions from the divergence of specific heat at constant volume is found. The new‐found condition is purely kinematic and quadratic in nature, relating the deceleration parameter and the jerk parameter that chalks out an interesting curve on the parameter space. This condition is valid even without the entropic source term and may be treated as a general property of any phase transition.
A photogrammetric methodology for estimating construction and demolition waste composition Conference Proceedings Joint 2002 Csce ASCE International Conference on Environmental Engineering an International Perspective on Environmental Engineering, 2002
