Instability of Quantum de Sitter Spacetime

TL;DR

This paper investigates how quantum effects, such as particle production in de Sitter spacetime, cause back-reaction that destabilizes the classical spacetime, contrasting with the stability observed in Anti-de Sitter space.

Contribution

It demonstrates that quantum-induced particle production leads to instability in de Sitter spacetime, highlighting differences with Anti-de Sitter space where such effects are absent.

Findings

Quantum particle production reduces de Sitter expansion rate

Back-reaction causes deviation from constant curvature

De Sitter spacetime becomes unstable under quantum perturbations

Abstract

Quantized fields (e.g., the graviton itself) in de Sitter (dS) spacetime lead to particle production: specifically, we consider a thermal spectrum resulting from the dS (horizon) temperature. The energy required to excite these particles reduces slightly the rate of expansion and eventually modifies the semiclassical spacetime geometry. The resulting manifold no longer has constant curvature nor time reversal invariance, and back-reaction renders the classical dS background unstable to perturbations. In the case of AdS, there exists a global static vacuum state; in this state there is no particle production and the analogous instability does not arise.