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Dirty black holes: quasinormal modes for ‘squeezed’ horizons. (English) Zbl 1055.83023

Summary: We consider the quasinormal modes for a class of black-hole spacetimes that, informally speaking, contain a closely ‘squeezed’ pair of horizons. (This scenario, where the relevant observer is presumed to be ‘trapped’ between the horizons, is operationally distinct from near-extremal black holes with an external observer.) It is shown, by analytical means, that the spacing of the quasinormal frequencies equals the surface gravity at the squeezed horizons. Moreover, we can calculate the real part of these frequencies provided that the horizons are sufficiently close together (but not necessarily degenerate). The novelty of our analysis (which extends a model-specific treatment by Cardoso and Lemos) is that we consider ’dirty’ black holes, that is, the observable portion of the (static and spherically symmetric) spacetime is allowed to contain an arbitrary distribution of matter.

MSC:

83C57 Black holes
83C05 Einstein’s equations (general structure, canonical formalism, Cauchy problems)
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