Constraining Lorentz Violation in Kalb-Ramond Gravity via Thermodynamics and Gravitational Wave Analysis

TL;DR

This paper explores how a Lorentz-violating Kalb-Ramond background affects black hole thermodynamics, shadow size, and gravitational wave signals, providing observational constraints using EHT data to test Planck-scale physics.

Contribution

It demonstrates that Lorentz violation in Kalb-Ramond gravity modifies black hole shadow and quasinormal modes, and constrains the Lorentz-violating parameter using observational data.

Findings

Thermodynamics remains consistent with GR, no entropy-area deviation.

Shadow radius is suppressed by factor of √(1-l), affecting imaging.

Constraint of l ≲ 0.19 from EHT observations.

Abstract

We investigate the observational signatures of a static, spherically symmetric black hole embedded in a spontaneous Kalb-Ramond (KR) background. By normalizing the solution to the physically observable mass $M_{\text{phys}}$, we demonstrate that the thermodynamics of the KR black hole are consistent with General Relativity, with no deviations in the entropy-area law. However, the Lorentz-violating parameter $l$ induces distinct geometric effects: it suppresses the optical shadow radius by a factor of $\sqrt{1-l}$ and hardens the quasinormal mode frequency by the inverse factor. Utilizing Event Horizon Telescope (EHT) data for Sagittarius A*, and assuming the mass prior derived from stellar dynamics, we place a constraint of $l \lesssim 0.19$. While the product of the shadow radius and ringdown frequency remains degenerate with General Relativity, the specific suppression of the shadow size offers a viable pathway to constrain Planck-scale physics with current and future horizon-scale imaging.