arXiv subjects

Bhera Ram

Publications and source records attributed to Bhera Ram.

4 recordsLinked to original sources

arXiv2026

Entropic route to Brown-York tensor: A unified framework for null and timelike hypersurfaces

Building on Padmanabhan's entropy functional, originally introduced to derive Einstein's equations and highlight the emergent nature of gravity, we demonstrate its robustness in a broader context. Using the same entropy density, we show that the Brown-York tensor is associated with a tangential projection of the entropy-functional polymomentum, thereby providing a common construction applicable to both timelike and null hypersurfaces. This perspective places the two (null and timelike) cases on the same variational footing and clarifies the structural differences of the null Brown-York tensor, including its generally non-symmetric character, without resorting to separate or ad hoc prescriptions in the formulation. We further extend the analysis to scalar-tensor theories, showing that the entropy-based formulation reproduces the expected equations of motion along with the corresponding BY tensor. Our results provide a coherent variational interpretation of quasi-local gravitational quantities and reveal a common underlying structure linking bulk dynamics and boundary momentum.

gr-qc↗

arXiv2025

Thermodynamic parameters of fluids on conformally connected spacetimes

Local thermal equilibrium generally implies the absence of heat flux within a fluid. We find the relations between a set of thermodynamic variables of a fluid on a general spacetime and those defined on a conformally connected spacetime, assuming both descriptions are at thermal equilibrium. The scaling relations appear to be consistent with Dicke's heuristic argument and the previous analysis done on the basis of various restrictions. Within the present framework, it is observed that the satisfaction of Klein's law on one of the spacetimes implies its validity on the other one. Moreover, our analysis bypasses some of the imposed restrictions and thereby reveals the generality of the earlier predictions. These relations are further shown to preserve the geometric structure of thermodynamics, known as geometrothermodynamics, such that the associated metrics on two conformally connected spacetimes are themselves conformally related. This provides an alternative consistency check as well as a distinct geometric interpretation of the relations.

gr-qc↗

arXiv2024

General relativistic heat flow from first order hydrodynamics

Following the recently proposed stable and causal first-order relativistic hydrodynamics by Bemfica, Disconzi, and Noronha, we find the heat flow equation in the presence of gravity for a non-viscous fluid, which suffers heat dissipation. The derivation is confined to static and stationary backgrounds. We find that in the presence of gravity, the heat flux times a redshift factor is conserved. Then for radial heat flow, the temperature profiles are obtained from the heat equation when the gravity is sourced by Schwarzschild, Schwarzschild-dS, Kerr and Kerr-dS black holes, respectively. Consequently, the chemical potential profile is also discussed.

gr-qc↗

arXiv2023

Laws of thermodynamic equilibrium within first order relativistic hydrodynamics

Using recently developed consistent and robust first order relativistic hydrodynamics of a dissipative fluid we propose a generalization but weak version of Tolman-Ehrenfest relation and Klein's law on a general background spacetime. These relations are appeared to be a consequence of thermal equilibrium state of the fluid, defined by the absence of heat flux. We interpret them as the defining relations for the local temperature and chemical potential of the fluid. The validity of usual Tolman-Ehrenfest relation and Klein's law deeply depends on the existence of a global timelike Killing vector. However imposition of more stronger equilibrium condition -- local conservation of entropy current -- yields the constancy of the equilibrium thermodynamic parameters along the flow lines.

gr-qc↗