Absorption and scattering of massless scalar waves by Frolov black holes

TL;DR

This paper investigates how massless scalar waves are absorbed and scattered by Frolov black holes, revealing the photon-sphere's role in high-frequency wave behavior and comparing these effects with other black hole models.

Contribution

It provides a detailed analysis of scalar wave interactions with Frolov black holes, highlighting photon-sphere influence and comparing absorption/scattering patterns across different black hole types.

Findings

High-frequency oscillations in absorption cross sections collapse onto a universal pattern.

Photon-sphere parameters largely determine scattering signatures.

Frolov, Reissner--Nordstr"om, and Hayward black holes show similar scattering features at high frequencies.

Abstract

We study the absorption and scattering of massless scalar waves by Frolov black holes, a regular deformation of the Reissner--Nordstr\"om geometry. A null-geodesic analysis provides the photon-sphere radius and the critical impact parameters governing capture and glory scattering. Using a partial-wave approach, we compute total/partial absorption cross sections and differential scattering cross sections over a broad frequency range. When the absorption spectrum is rescaled by photon-sphere scales, the high-frequency oscillations exhibit a pronounced data collapse in the variables $\hat{\sigma}=\sigma_{\rm abs}/\sigma_{\rm geo}$ and $x=\omega/\Omega_c$, highlighting photon-sphere control of the absorption fine structure. We clarify the parameter dependence under the horizon-radius normalization and relate the apparent trends to the variation of the dimensionless mass across parameter space. Finally, comparing Frolov, Reissner--Nordstr\"om, and Hayward black holes with matched critical or glory impact parameters, we find that their absorption and scattering patterns can become remarkably close, indicating that in the intermediate-to-high frequency regime the dominant signatures are largely governed by the unstable photon orbit, while core effects enter as subleading corrections.