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GR: Fachverband Gravitation und Relativitätstheorie

GR 6: Black Holes and other Black Objects

GR 6.1: Hauptvortrag

Dienstag, 1. März 2016, 16:45–17:25, VMP6 HS A

A No-Hair Theorem for Astrophysically Relevant Black Holes — •Norman Gürlebeck — ZARM, University of Bremen, Germany

With the upcoming capabilities to observe black holes, it will be feasible to measure their properties with unprecedented detail. In particular, it will become possible to carry out so-called tests of the no-hair theorem. The no-hair theorem states that black holes are entirely characterized by their mass, angular momentum and charge alone. For this result to hold, the black hole must be isolated, i.e., there should be no additional sources of the gravitational field in their neighborhood like accretion disks. However, measurements of the angular momentum of the black hole rely heavily on the existence of such an accretion disk. Naturally, the question arises if the additional matter, say, an accretion disk impedes the suggested tests of the no-hair theorem. I will give a possible formulation of the no-hair theorem for such astrophysical black holes surrounded by matter alongside with a proof for static black holes. The proof employs the source integral formalism, which I review shortly. Perturbative approaches showed that deformations of black holes, which are immersed in an external gravitational field, measured by the second Love numbers vanish. But there was no consensus whether this result is still valid in case higher orders of the perturbation schemes are considered. The here presented no-hair theorem also implies that the second Love numbers of black holes vanish in full general relativity settling this debate also for the strong field regime. In the end of my talk, I will apply the developed formalism to existence and uniqueness questions in mathematical relativity.