A superradiance resonance cavity outside rapidly rotating black holes

TL;DR

This paper analyzes the late-time behavior of perturbed Kerr black holes, revealing a 1/t decay in oscillation amplitude due to a superradiance resonance cavity, supported by analytic and numerical evidence.

Contribution

It introduces the concept of a superradiance resonance cavity outside rapidly rotating black holes and provides analytic and numerical analysis of late-time decay behavior.

Findings

Oscillation amplitude decays as 1/t at late times.

Presence of a superradiance resonance cavity influences black hole perturbations.

Analytic results are verified with numerical simulations.

Abstract

We discuss the late-time behaviour of a dynamically perturbed Kerr black hole. We present analytic results for near extreme Kerr black holes that show that the large number of virtually undamped quasinormal modes that exist for nonzero values of the azimuthal eigenvalue m combine in such a way that the field oscillates with an amplitude that decays as 1/t at late times. This prediction is verified using numerical time-evolutions of the Teukolsky equation. We argue that the observed behaviour may be relevant for astrophysical black holes, and that it can be understood in terms of the presence of a ``superradiance resonance cavity'' immediately outside the black hole.