English

Particle Dynamics, Shadow and Hawking Sparsity of a Kalb-Ramond Black Hole Coupled to Nonlinear Electrodynamics

General Relativity and Quantum Cosmology 2026-05-19 v1 High Energy Astrophysical Phenomena High Energy Physics - Theory

Abstract

We study the timelike and null geodesic structure of a static, spherically symmetric black hole sourced by a Kalb--Ramond (KR) field coupled to nonlinear electrodynamics (NED). The geometry is characterized by the mass MM, the magnetic monopole charge qq, and the Lorentz-violating parameters (γ,λ)(\gamma,\lambda). Closed-form expressions are derived for the effective potential, as well as the specific energy and angular momentum of massive particles on circular orbits. We further analyze the photon sphere, black hole shadow, and the Lyapunov exponent associated with unstable null circular geodesics. The latter determines the eikonal quasinormal-mode frequencies through ωeik=(+1/2)Ωci(n+1/2)λL\omega_{\rm eik}=(\ell+1/2)\,\Omega_c-i(n+1/2)\,|\lambda_L|. The shadow radius is compared with the Event Horizon Telescope (EHT) observations of M87^\ast and Sgr~A^\ast, allowing us to identify the viable region in the (q,γ)(q,\gamma) parameter space. Finally, we compute the Hawking temperature, horizon area, and the Gray--Visser sparsity parameter. We demonstrate that the combined effects of the KR field and magnetic monopole charge increase the sparsity parameter from the Schwarzschild value 16π349616\pi^3 \simeq 496 to nearly 1.7×1031.7\times10^3. This indicates a significantly sparser Hawking cascade compared to the Schwarzschild case, while the photon ring remains consistent with the EHT 1σ1\sigma observational bounds across most of the physically allowed parameter range.

Keywords

Cite

@article{arxiv.2605.16461,
  title  = {Particle Dynamics, Shadow and Hawking Sparsity of a Kalb-Ramond Black Hole Coupled to Nonlinear Electrodynamics},
  author = {Faizuddin Ahmed and Ahmad Al-Badawi and İzzet Sakallı},
  journal= {arXiv preprint arXiv:2605.16461},
  year   = {2026}
}

Comments

12 pages. Comments are welcome