Infrared instability of the de Sitter space

TL;DR

The work demonstrates that quantum instabilities in de Sitter backgrounds arise from $IR/UV$ mixing, making $in/in$ perturbation theory effectively non-renormalizable in many cases. By analyzing electric-field analogies, Poincaré/Anti-Poincaré patches, and Schwinger–Keldysh dynamics, it uncovers secular infrared growth and backreaction in both global and patchwise de Sitter spaces, with distinct behavior between even and odd spacetime dimensions. The author proposes a kinetic, logarithm-resummation framework via a Green-function ansatz to capture leading secular effects and discusses the need to include gravitons and gauge degrees of freedom for a complete picture. These results point to a quantum instability of de Sitter spaces with potential implications for cosmology and inflation, highlighting open questions about nonperturbative dynamics and the fate of de Sitter backgrounds.

Abstract

We continue to investigate various instabilities of the fixed backgrounds related to the de Sitter space. It is shown that in many cases the in/in perturbation theory contains IR/UV mixing and thus is non-renormalizible. The application of this result to the global de Sitter space leads to the conclusion that even massive particles generate IR divergence and the huge back reaction. The expanding universe is also unstable but in a weaker sense. We further discuss, the strange features of the Gibbons-Hawking radiation and its relation to the above instabilities. .