title: Superradiance resonance cavity outside rapidly rotating black holes
abstract: We discuss the late-time behavior 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 behavior can be understood in terms of the presence of a "superradiance resonance cavity" immediately outside the black hole, and discuss whether it may be relevant for astrophysical black holes.
authors.affiliation: Department of Mathematics, University of Southampton, Southampton SO17 1BJ, United Kingdom.
authors.initials: N
authors.lastname: Andersson
authors.initials: K
authors.lastname: Glampedakis