Feeling de Sitter

TL;DR

This paper investigates whether a quantum field can detect its transition into de Sitter space by analyzing the evolution of two-point correlation functions, revealing insights into the equilibration process in curved spacetime.

Contribution

It applies non-equilibrium quantum field theory to study the time evolution of quantum states transitioning into de Sitter space, highlighting how different observables approach equilibrium.

Findings

Correlation functions tend to approach Bunch-Davies values over time

The equilibration process resembles that in familiar quantum systems

Detection depends on the specific quantities examined

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 $\eta<\eta_0$, and then evolves in a de Sitter background turned on instantaneously at $\eta=\eta_0$. 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.