Quantum cosmology and recollapse

Abstract

The wave function of the Universe defined by the Hartle-Hawking proposal is studied for two minisuperspace models, the Friedmann-Robertson-Walker universe with a massive scalar field and the anisotropic Kantowski-Sachs cosmology. Solutions of the Wheeler-DeWitt equation are evaluated numerically. We also examine the trajectories to which these correspond in the classical limit. Attention is focused on the fact that most classical trajectories recollapse to a singularity. They will add an oscillatory component to the wave function in the region of small three-volume where it is predominantly exponential. They will thus modify the original boundary conditions. The Kantowski-Sachs universes generically evolve from isotropy during expansion to increasing anisotropy during recollapse, ending as a black-hole interior. We comment, therefore, on the arrow of time naturally induced by the Hartle-Hawking proposal.