Black holes in anti-de Sitter spacetime: Quasinormal modes, tails, and flat spacetime

Black holes (BHs) 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 nonexistant. We close this gap by evolving linearized scalar wave packets 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 wave packets in the vicinity of fast spinning BHs grow exponentially in time, signaling a superradiant instability of the geometry previously reported through a frequency-domain analysis.