Scattering of electromagnetic field in quasi-topological gravity

TL;DR

This paper studies how higher-curvature corrections and spacetime dimensions in quasi-topological gravity affect electromagnetic wave scattering and absorption by regular black holes, revealing deviations from classical solutions.

Contribution

It introduces a detailed analysis of electromagnetic absorption in regular black holes within quasi-topological gravity, highlighting the effects of regularity and higher-curvature terms on scattering spectra.

Findings

Regularity causes deviations from Tangherlini black holes in absorption spectra.

Increasing dimensions reduces deviations and simplifies multipole convergence.

High-frequency absorption approaches geometric optics, low-frequency is suppressed.

Abstract

We investigate the absorption cross sections of electromagnetic perturbations propagating on a four-dimensional brane in the background of higher-dimensional regular black holes arising in quasi-topological gravity. Employing a WKB-based approach for the computation of greybody factors, we analyze the impact of higher-curvature corrections and spacetime dimensionality on the scattering properties of the system. We show that regularity effects lead to systematic deviations from the singular Tangherlini solution, manifested in shifts of the absorption spectrum and modifications of the effective photon sphere radius. Increasing the number of spacetime dimensions suppresses these deviations, driving the system toward the classical limit and reducing the number of multipoles required for convergence. In the high-frequency regime, the absorption cross section approaches the geometric-optics limit, while at low frequencies it is strongly suppressed due to diminished transmission probabilities. Our results demonstrate that the interplay between regularity and higher-curvature effects leaves distinct imprints on the absorption characteristics, providing a sensitive probe of the underlying gravitational theory.