Generalized Slow Roll for Large Power Spectrum Features

TL;DR

This paper introduces a refined generalized slow roll method for accurately calculating the curvature power spectrum in inflation models with sharp potential features, enabling better analysis of CMB anomalies.

Contribution

It develops a new variant of the generalized slow roll approach that handles order unity deviations and relates observable features to inflaton potential properties.

Findings

Accurate percent-level predictions for step potential models.

Identification of a single source function linked to potential slope and curvature.

Applicability to inflation-model independent feature analysis.

Abstract

We develop a variant of the generalized slow roll approach for calculating the curvature power spectrum that is well-suited for order unity deviations in power caused by sharp features in the inflaton potential. As an example, we show that predictions for a step function potential, which has been proposed to explain order unity glitches in the CMB temperature power spectrum at multipoles l=20-40, are accurate at the percent level. Our analysis shows that to good approximation there is a single source function that is responsible for observable features and that this function is simply related to the local slope and curvature of the inflaton potential. These properties should make the generalized slow roll approximation useful for inflation-model independent studies of features, both large and small, in the observable power spectra.