Nonperturbative semiclassical stability of de Sitter spacetime for small metric deviations

TL;DR

This paper demonstrates the nonperturbative stability of de Sitter spacetime against small metric deviations by solving the semiclassical Einstein equations with quantum effects, showing de Sitter as a late-time attractor.

Contribution

It provides exact solutions to the linearized semiclassical Einstein equations including quantum effects, establishing de Sitter stability beyond perturbation theory.

Findings

De Sitter spacetime is stable under small metric deviations.

Exact solutions show de Sitter as a late-time attractor.

Perturbative solutions break down over long evolution inside the horizon.

Abstract

We consider the linearized semiclassical Einstein equations for small deviations around de Sitter spacetime including the vacuum polarization effects of conformal fields. Employing the method of order reduction, we find the exact solutions for general metric perturbations (of scalar, vector and tensor type). Our exact (nonperturbative) solutions show clearly that in this case de Sitter is stable with respect to small metric deviations and a late-time attractor. Furthermore, they also reveal a breakdown of perturbative solutions for a sufficiently long evolution inside the horizon. Our results are valid for any conformal theory, even self-interacting ones with arbitrarily strong coupling.