Feeling de Sitter

Abstract

We address the following question: To what extent can a quantum field tell if it has been placed in de Sitter space? Our approach is to use the techniques of non-equilibrium quantum field theory to compute the time evolution of a state which starts off in flat space for (conformal) times $η<η_0$, and then evolves in a de Sitter background turned on instantaneously at $η=η_0$. We find that the answer depends on what quantities one examines. We study a range of them, all based on two-point correlation functions, and analyze which ones approach the standard Bunch-Davies values over time. The outcome of this analysis suggests that the nature of the equilibration process in this system is similar to that in more familiar systems.

25 pages, 11 figures. V2: Final version accepted for publication in PRD. Changes: References added and minor clarifications to the presentation