Gravitational collapse with a cosmological constant - art. no. 084029

We consider the effect of a positive cosmological constant on spherical gra vitational collapse to a black hole for a few simple, analytic cases. We co nstruct the complete Oppenheimer-Snyder-de Sitter (OSdS) spacetime. the gen eralization of the Oppenheimer-Snyder solution for collapse from rest of a homogeneous dust ball in an exterior vacuum. In OSdS collapse, the cosmolog ical constant may affect the onset of collapse and decelerate the implosion initially, but it plays a diminishing role as the collapse proceeds. We al so construct spacetimes in which a collapsing dust ball can bounce, or hove r in unstable equilibrium due to the repulsive force of the cosmological co nstant. We explore the causal structure of the different spacetimes and ide ntify any cosmological and black hole event horizons which may be present.