Generalized Slow Roll for Non-Canonical Kinetic Terms

TL;DR

This paper extends the generalized slow-roll method to models with non-canonical kinetic terms, enabling analysis of features like rapid sound speed variations in the power spectrum.

Contribution

It introduces a unified approach to handle non-canonical inflation models with non-slowly varying parameters, linking deviations directly to the power spectrum.

Findings

Applicable to models with rapid sound speed changes

Provides a simple relation between source function and power spectrum

Facilitates empirical interpretation of features in inflation models

Abstract

We show that the generalized slow-roll approach for calculating the power spectrum where the inflationary slow roll parameters are neither small nor slowly varying can be readily extended to models with non-canonical kinetic terms in the inflaton action. For example, rapid sound speed variations can arise in DBI models with features in the warp factor leading to features in the power spectrum. Nonetheless there remains a single source function for deviations that is simply related to the power spectrum. Empirical constraints on this source function can be readily interpreted in the context of features in the inflaton potential or sound speed.