Semiclassical relations and IR effects in de Sitter and slow-roll space-times

TL;DR

This paper investigates IR divergences in de Sitter space and slow-roll inflation, showing that semiclassical relations can reproduce leading IR effects, which significantly impact inflationary predictions and suggest non-perturbative physics.

Contribution

It introduces semiclassical consistency relations to compute IR effects in de Sitter and slow-roll inflation, revealing their importance and potential breakdown of perturbation theory.

Findings

IR corrections can be of order unity in prolonged inflation

These corrections modify tensor/scalar ratios and non-Gaussianity parameters

Perturbation theory may break down, indicating need for non-perturbative approaches

Abstract

We calculate IR divergent graviton one-loop corrections to scalar correlators in de Sitter space, and show that the leading IR contribution may be reproduced via simple semiclassical consistency relations. One can likewise use such semiclassical relations to calculate leading IR corrections to correlators in slow-roll inflation. The regulated corrections shift the tensor/scalar ratio and consistency relation of single field inflation, and non-gaussianity parameters averaged over very large distances. For inflation of sufficient duration, for example arising from a chaotic inflationary scenario, these corrections become of order unity. First-order corrections of this size indicate a breakdown of the perturbative expansion, and suggest the need for a non-perturbative description of the corresponding regime. This is analogous to a situation argued to arise in black hole evolution, and to interfere with a sharp perturbative calculation of "missing information" in Hawking radiation.