Space-like Singularities and Thermalization

Abstract

We conjecture that space-like singularities are simply regions in which all available degrees of freedom are excited, and the system cycles randomly through generic quantum states in its Hilbert space. There is no simple geometric description of the interior of such a region, but if it is embedded in a semi-classical space-time an external observer sees it as a black hole. Big Bang and Crunch singularities, for which there is no such embedding, must be described in purely quantum terms. We present several possible descriptions of such cosmologies.