The enigmatic gravitational partition function

Abstract

The saddle point approximation to formal quantum gravitational partition functions has yielded plausible computations of horizon entropy in various settings, but it stands on shaky ground. In this paper we visit some of that shaky ground, address some foundational questions, and describe efforts toward a more solid footing. We focus on the case of de Sitter horizon entropy which, it has been argued, corresponds to the dimension of the Hilbert space of a ball of space surrounded by the cosmological horizon.