Tuning, Ergodicity, Equilibrium and Cosmology

Abstract

I explore the possibility that the cosmos is fundamentally an equilibrium system, and review the attractive features of such theories. Equilibrium cosmologies are commonly thought to fail due to the ``Boltzmann Brain'' problem. I show that it is possible to evade the Boltzmann Brain problem if there is a suitable coarse grained relationship between the fundamental degrees of freedom and the cosmological observables. I make my main points with simple toy models, and then review the de Sitter equilibrium model as an illustration.