Brickwall, normal modes, and emerging thermality

Abstract

In this paper, we demonstrate how black hole quasinormal modes can emerge from a Dirichlet brickwall model normal modes. We consider a probe scalar field in a Baños-Teitelboim-Zanelli geometry with a Dirichlet brickwall and demonstrate that as the wall approaches the event horizon, the corresponding poles in the retarded correlator become dense and yield an effective branch cut. The associated discontinuity of the correlator carries the information of the black hole quasinormal modes. We further demonstrate that a nonvanishing angular momentum nonperturbatively enhances the pole condensing. We hypothesize that it is also related to quantum chaotic features of the corresponding spectral form factor, which has been observed earlier. Finally, we discuss the underlying algebraic justification of this approximate thermalization in terms of the trace of the algebra. Published by the American Physical Society 2024