Black holes in anti-de Sitter: quasinormal modes, tails and tales of flat spacetime

TL;DR

This paper investigates linearized scalar perturbations around rotating black holes in anti-de Sitter spacetime, revealing early flat spacetime behavior, mode settling, and potential superradiant instabilities.

Contribution

It provides the first time-domain evolution of scalar wavepackets in rotating AdS black hole backgrounds, highlighting new dynamical features and stability insights.

Findings

Small AdS black holes behave like flat spacetime black holes initially.

Wavepackets settle into AdS modes after bouncing between horizon and boundary.

Indications of exponential growth near fast-spinning black holes suggest superradiant instability.

Abstract

Black holes in asymptotically anti-de Sitter (AdS) spacetimes have been the subject of intense scrutiny, including detailed frequency-domain analysis and full nonlinear evolutions. Remarkably, studies of linearized perturbations in the time-domain are scarce or non-existing. We close this gap by evolving linearized scalar wavepackets in the background of rotating BHs in AdS spacetimes. Our results show a number of interesting features. Small BHs in AdS behave as asymptotically flat BHs for early/intermediate times, displaying the same ringdown modes and power-law tails. As the field bounces back and forth between the horizon and the timelike boundary it "thermalizes" and the modes of AdS settle in. Finally, we have indications that wavepackets in the vicinity of fastly spinning BHs grow exponentially in time, signalling a superradiant instability of the geometry previously reported through a frequency-domain analysis.