Colliding waves and black holes

Abstract

A particular colliding plane gravitational wave solution is, in the interaction region, a portion of a covering space of the Schwarzschild solution inside the white hole, excluding the singularity. A time-reversed extension exists including covering spaces of the Schwarzschild exteriors and part of the black hole, and ultimately giving two receding waves with flat space between. Equivalently, the normal Schwarzschild exterior may be extended inside the black and white holes to compactified plane-wave regions with flat space between. This extension compares well with the usual Kruskal extension in that it is almost complete and without curvature singularities apart from shock waves. Similar extensions exist for the general Kerr-Newman case.