Loop effects and infrared divergences in slow-roll inflation

TL;DR

This paper investigates loop corrections in slow-roll inflation, showing they diverge at most logarithmically, and derives constraints on inflationary models to ensure the validity of perturbation theory.

Contribution

It extends Weinberg's theorem to quasi-single field inflation and establishes new constraints on inflationary vacua from perturbation theory validity.

Findings

Loop corrections diverge no worse than powers of log of scale factor

Constraints on effective Lagrangian for valid perturbation theory

Implications for the landscape of inflationary vacua

Abstract

Loop corrections to observables in slow-roll inflation are found to diverge no worse than powers of the log of the scale factor, extending Weinberg's theorem to quasi-single field inflation models. Demanding perturbation theory be valid during primordial inflation leads to constraints on the effective lagrangian. This leads to some interesting constraints and coincidences on the landscape of inflationary vacua.