Massive scalar field evolution in de Sitter

TL;DR

This paper studies the evolution of a massive scalar field in de Sitter space, showing stability and potential for super-acceleration due to quantum effects without assuming a vacuum state.

Contribution

It provides a vacuum-independent analysis of scalar field dynamics in de Sitter space, revealing stability and conditions for energy condition violations.

Findings

De Sitter space is stable under small scalar field perturbations.

Energy density can approach its limit from above or below, affecting energy conditions.

Quantum backreaction may induce super-acceleration phases.

Abstract

The behaviour of a massive, non-interacting and non-minimally coupled quantised scalar field in an expanding de Sitter background is investigated by solving the field evolution for an arbitrary initial state. In this approach there is no need to choose a vacuum in order to provide a definition for particle states. We conclude that the expanding de Sitter space is a stable equilibrium configuration under small perturbations of the initial conditions. Depending on the initial state, the energy density can approach its asymptotic value from above or below, the latter of which implies a violation of the weak energy condition. The backreaction of the quantum corrections can therefore lead to a phase of super-acceleration also in the non-interacting massive case.