Branch structure and nonextensive thermodynamics of Kalb-Ramond-ModMax black holes: observational signatures

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Main Authors: Sucu, Erdem, Sakalli, Izzet, Saridakis, Emmanuel N.
Format: Preprint
Published: 2026
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author Sucu, Erdem
Sakalli, Izzet
Saridakis, Emmanuel N.
author_facet Sucu, Erdem
Sakalli, Izzet
Saridakis, Emmanuel N.
contents We investigate a static, spherically symmetric black hole arising in Einstein gravity coupled to a Kalb-Ramond field and ModMax nonlinear electrodynamics, both of which are independently well motivated extensions of standard electrovacuum gravity. The solution depends, beyond mass and charge, on a Lorentz-violating parameter, a ModMax deformation parameter, and a discrete branch selector $ζ=\pm1$. We show that the ordinary branch admits extremal and non-extremal configurations, while the phantom branch generically supports a single-horizon geometry. Black-hole thermodynamics is analyzed within the Tsallis non-extensive framework, revealing branch-dependent stability and Joule-Thomson behavior. Weak gravitational lensing is analyzed using the Ono-Ishihara-Asada extension of the Gauss-Bonnet theorem, which is required by the non-Euclidean asymptotic structure of the Kalb-Ramond optical geometry and yields a negative topological correction that reduces light bending relative to the Schwarzschild baseline. Photon propagation in plasma and tidal forces are also studied, revealing clear optical and strong-field signatures that distinguish the two branches.
format Preprint
id arxiv_https___arxiv_org_abs_2601_20004
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Branch structure and nonextensive thermodynamics of Kalb-Ramond-ModMax black holes: observational signatures
Sucu, Erdem
Sakalli, Izzet
Saridakis, Emmanuel N.
General Relativity and Quantum Cosmology
High Energy Physics - Theory
We investigate a static, spherically symmetric black hole arising in Einstein gravity coupled to a Kalb-Ramond field and ModMax nonlinear electrodynamics, both of which are independently well motivated extensions of standard electrovacuum gravity. The solution depends, beyond mass and charge, on a Lorentz-violating parameter, a ModMax deformation parameter, and a discrete branch selector $ζ=\pm1$. We show that the ordinary branch admits extremal and non-extremal configurations, while the phantom branch generically supports a single-horizon geometry. Black-hole thermodynamics is analyzed within the Tsallis non-extensive framework, revealing branch-dependent stability and Joule-Thomson behavior. Weak gravitational lensing is analyzed using the Ono-Ishihara-Asada extension of the Gauss-Bonnet theorem, which is required by the non-Euclidean asymptotic structure of the Kalb-Ramond optical geometry and yields a negative topological correction that reduces light bending relative to the Schwarzschild baseline. Photon propagation in plasma and tidal forces are also studied, revealing clear optical and strong-field signatures that distinguish the two branches.
title Branch structure and nonextensive thermodynamics of Kalb-Ramond-ModMax black holes: observational signatures
topic General Relativity and Quantum Cosmology
High Energy Physics - Theory
url https://arxiv.org/abs/2601.20004