Quantum Gravity and Inflation

TL;DR

This paper reviews quantum gravity effects during inflation, introduces non-local gravitational models that reproduce infrared effects, and explores their implications for ending inflation, reheating, and the cosmological constant.

Contribution

It proposes a new class of non-local gravitational models that capture quantum infrared effects and connect inflation to late-time acceleration.

Findings

Models reproduce leading infrared logarithms of quantum back-reaction.

They end inflation with oscillations and slight energy condition violations.

One model predicts a small positive cosmological constant.

Abstract

We review some perturbative results obtained in quantum gravity in an accelerating cosmological background. We then describe a class of non-local, purely gravitational models which have the correct structure to reproduce the leading infrared logarithms of quantum gravitational back-reaction during the inflationary regime. These models end inflation in a distinctive phase of oscillations with slight and short violations of the weak energy condition and should, when coupled to matter, lead to rapid reheating. By elaborating this class of models we exhibit one that has the same behaviour during inflation, goes quiescent until the onset of matter domination, and induces a small, positive cosmological constant of about the right size thereafter. We also briefly comment on the primordial density perturbations that this class of models predict.