The thermal backreaction of a scalar field in de Sitter spacetime

TL;DR

This paper investigates how a scalar field in de Sitter spacetime experiences thermal effects due to curvature, computes the resulting energy-momentum tensor, and analyzes its backreaction on the spacetime geometry.

Contribution

It introduces a method to compute thermal effects of a scalar field in de Sitter space using thermo-field dynamics and examines their impact on spacetime backreaction.

Findings

Thermal effects depend on initial conditions.

Backreaction can alter the de Sitter geometry.

Results are compared to quantum gravity corrections.

Abstract

We argue that a scalar field in de Sitter spacetime should feel explicit thermal effects associated with its curvature. Starting from the Bunch-Davies vacuum and a scalar field with small mass compared to the de Sitter curvature, we use the thermo-field dynamics formalism in order to expose these thermal effects. We compute the thermal Wightman function connecting two spacetime points and from it, via the point-splitting regularization technique, the renormalized thermal energy-momentum tensor. We then examine how these corrections affect the de Sitter geometry by solving for the semi-classical backreaction and find that their sign depends on the initial conditions. In order to place our results in context, we compare them to the corresponding 2-loop quantum gravity correction to the cosmological constant derived in [1].