Black-hole collisions as sources of gravitational radiation

Abstract

Black-hole collisions are discussed in terms of general conservation principles. The approach originally suggested by Hawking is extended to charged black holes; the event horizon area is found to increase, as it does in the case of neutral objects. The upper limit for the efficiency of gravitational radiation emitted in a reversible process turns out to be 1 -√1-e2/(2m2)/2. It is shown than the conservation of the irreducible mass is a more restrictive condition that the conservation of the surface area.