One-loop corrections to the curvature perturbation from inflation

TL;DR

This paper estimates the one-loop quantum corrections to the primordial curvature perturbation's power spectrum during single-field slow-roll inflation, highlighting potential issues with perturbation theory validity for CMB predictions.

Contribution

It provides a detailed calculation of the one-loop correction, separating quantum and classical parts, and discusses implications for inflationary predictions.

Findings

Loop correction includes quantum and classical parts.

Logarithmic terms may challenge perturbation theory validity.

Results impact CMB scale predictions.

Abstract

An estimate of the one-loop correction to the power spectrum of the primordial curvature perturbation is given, assuming it is generated during a phase of single-field, slow-roll inflation. The loop correction splits into two parts, which can be calculated separately: a purely quantum-mechanical contribution which is generated from the interference among quantized field modes around the time when they cross the horizon, and a classical contribution which comes from integrating the effect of field modes which have already passed far beyond the horizon. The loop correction contains logarithms which may invalidate the use of naive perturbation theory for cosmic microwave background (CMB) predictions when the scale associated with the CMB is exponentially different from the scale at which the fundamental theory which governs inflation is formulated.