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Black holes; general relativity; cosmology

The usual definition of a black hole is modified to make it applicable in a globally hyperbolic space-time. It is shown that in a closed globally hyperbolic universe the surface area of a black hole must eventually decrease. The implications of this breakdown of the black hole area theorem are discussed in the context of thermodynamics and cosmology. A modified definition of surface gravity is also given for non-stationary universes. The limitations of these concepts are illustrated by the explicit example of the Kerr-Vaidya metric.

P S Joshi¹ J V Narlikar¹

1. Tata Institute of Fundamental Research, Bombay - 400 005, India

Published

May 1982

Manuscript received

13 July 1981

Manuscript revised

16 February 1982