Power-counting and the Validity of the Classical Approximation During Inflation

TL;DR

This paper uses effective field theory power-counting to analyze loop corrections in slow-roll inflation, clarifying the validity limits of classical inflationary models, especially in Higgs-Inflaton and curvature-squared scenarios.

Contribution

It systematically identifies the most significant quantum corrections to classical inflationary dynamics using a general effective field theory approach.

Findings

Most slow-roll models remain within the semiclassical domain.

Higgs-Inflaton scenario's consistency is more delicate due to scale proximity.

Curvature-squared inflation models face similar validity issues.

Abstract

We use the power-counting formalism of effective field theory to study the size of loop corrections in theories of slow-roll inflation, with the aim of more precisely identifying the limits of validity of the usual classical inflationary treatments. We keep our analysis as general as possible in order to systematically identify the most important corrections to the classical inflaton dynamics. Although most slow-roll models lie within the semiclassical domain, we find the consistency of the Higgs-Inflaton scenario to be more delicate due to the proximity between the Hubble scale during inflation and the upper bound allowed by unitarity on the new-physics scale associated with the breakdown of the semiclassical approximation within the effective theory. Similar remarks apply to curvature-squared inflationary models.