TOPOLOGY CHANGE IN (2+1)-DIMENSIONAL GRAVITY

In (2+1)-dimensional general relativity the path integral for a manifo ld M can be expressed in terms of a topological invariant, the Ray-Sin ger torsion of a flat bundle over M. For some manifolds, this makes an explicit computation of transition amplitudes possible. In this paper , the amplitude for a simple topology-changing process is evaluated. I t is shown that certain amplitudes for spatial topology change are non vanishing-in fact, they can be infrared divergent-but that they are in finitely suppressed relative to similar topology-preserving amplitudes .