Piotr T. Chrusciel, Robert M. Wald
On the Topology of Stationary Black Holes
The paper is published: Classical Quantum Gravity 11, 12 (1994) L147-L152

MSC:

83C57 Black holes

Abstract: We prove that the domain of outer communication of a stationary,
globally hyperbolic spacetime
satisfying the null energy condition must be simply connected. Under
suitable additional hypotheses,
this implies, in particular, that each connected component of a
cross-section of the event horizon of a stationary black hole must
have spherical topology.

Keywords: event horizon, stationary black holes, topological censorship