Superradiant scattering by rotating black-bounce black holes

TL;DR

This paper studies how superradiant scattering behaves around rotating black-bounce black holes, revealing how specific parameters influence amplification and identifying configurations with significantly increased superradiance compared to Kerr black holes.

Contribution

It introduces a generalized black-bounce metric for rotating black holes and analyzes superradiant scattering, highlighting the effects of deformation parameters on amplification.

Findings

Increasing n enhances superradiance

Increasing k suppresses superradiance

Amplification up to 98% larger than Kerr

Abstract

We investigate superradiant scattering off a rotating regular black hole described by a black-bounce metric which generalizes the Kerr spacetime of mass $M$ and specific angular momentum $a$ through a regularization parameter $p$ and two deformation exponents $(k,n)$. Focusing on massless $(\ell,m)=(1,1)$ scalar modes, we explore the parameter space and compute amplification factors by numerically integrating the separated radial Klein-Gordon equation. We track the peak amplification and the corresponding frequency across the $(a/M,p/M)$ parameter space for several combinations of $k$ and $n$. We find that increasing $n$ systematically enhances superradiance, whereas increasing $k$ tends to suppress it. In particular, certain configurations yield amplification levels up to 98% larger than the maximum amplification for standard Kerr black holes.