Topological censorship and the topology of black holes

A new result on topological censorship is presented. Roughly speaking, the result shows that, under suitable conditions, the topology of space outside the event horizon must eventually be simple. In particular, cross sections of the event horizon must eventually be spherical. This latter consequence of the main result generalizes in many respects the classical theorem of Hawking that black hole boundaries in stationary black hole space–times are spherical.