Please use this identifier to cite or link to this item: http://hdl.handle.net/10773/18983
Title: Synchronous frequencies of extremal Kerr black holes: Resonances, scattering, and stability
Author: Richartz, M.
Herdeiro, C. A. R.
Berti, E.
Issue Date: 2017
Publisher: American Physical Society
Abstract: The characteristic damping times of the natural oscillations of a Kerr black hole become arbitrarily large as the extremal limit is approached. This behavior is associated with the so-called zero damped modes (ZDMs), and suggests that extremal black holes are characterized by quasinormal modes whose frequencies are purely real. Since these frequencies correspond to oscillations whose angular phase velocity matches the horizon angular velocity of the black hole, they are sometimes called "synchronous frequencies." Several authors have studied the ZDMs for near-extremal black holes. Recently, their correspondence to branch points of the Green's function of the wave equation was linked to the Aretakis instability of extremal black holes. Here we investigate the existence of ZDMs for extremal black holes, showing that these real-axis resonances of the field are unphysical as natural black hole oscillations: the corresponding frequency is always associated with a scattering mode. By analyzing the behavior of these modes near the event horizon we obtain new insight into the transition to extremality, including a simple way to understand the Aretakis instability.
Peer review: yes
URI: http://hdl.handle.net/10773/18983
DOI: 10.1103/PhysRevD.96.044034
ISSN: 2470-0010
Appears in Collections:CIDMA - Artigos
DFis - Artigos
GGDG - Artigos

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