Superradiant instabilities in the Kerr-mirror and Kerr-AdS black holes with Robin boundary conditions

作     者：Hugo R. C. Ferreira Carlos A. R. Herdeiro 

作者机构：Istituto Nazionale di Fisica Nucleare—Sezione di Pavia Via Bassi 6 27100 Pavia Italy Departamento de Física da Universidade de Aveiro and Center for Research and Development in Mathematics and Applications (CIDMA) Campus de Santiago 3810-183 Aveiro Portugal 

出 版 物：《Physical Review D》 (Phy. Rev. D)

年 卷 期：2018年第97卷第8期

页      面：084003-084003页

核心收录：

基　　金：GNFM-INdAM FCT-IF Instituto Nazionale di Fisica Nucleare, INFN Gruppo Nazionale per la Fisica Matematica, GNFM Istituto Nazionale di Alta Matematica "Francesco Severi", INdAM Horizon 2020 Framework Programme, H2020, (690904, 777740) Center for Research and Development in Mathematics and Applications, CIDMA, (UID/MAT/04106/2013) 

主　　题：Classical black holes Fluids & classical fields in curved spacetime 

摘      要：It has been recently observed that a scalar field with Robin boundary conditions (RBCs) can trigger both a superradiant and a bulk instability for a Bañados-Teitelboim-Zanelli (BTZ) black hole (BH) [1]. To understand the generality and scrutinize the origin of this behavior, we consider here the superradiant instability of a Kerr BH confined either in a mirrorlike cavity or in anti-de Sitter (AdS) space, triggered also by a scalar field with RBCs. These boundary conditions are the most general ones that ensure the cavity/AdS space is an isolated system and include, as a particular case, the commonly considered Dirichlet boundary conditions (DBCs). Whereas the superradiant modes for some RBCs differ only mildly from the ones with DBCs, in both cases, we find that as we vary the RBCs the imaginary part of the frequency may attain arbitrarily large positive values. We interpret this growth as being sourced by a bulk instability of both confined geometries when certain RBCs are imposed to either the mirrorlike cavity or the AdS boundary, rather than by energy extraction from the BH, in analogy with the BTZ behavior.