Constraining fast-roll inflation

TL;DR

This paper investigates the limits of fast-roll inflation models by analyzing their non-Gaussian signatures and employing observational constraints to establish bounds on single field inflation theories.

Contribution

It introduces a method to constrain fast-roll inflation by linking non-Gaussianities to weak-coupling conditions and observational data.

Findings

Fast-roll inflation models produce large, scale-dependent non-Gaussianities.

WMAP data constrains the parameter space of $P(X,\phi)$ inflation models.

Weak-coupling requirements limit the extent of possible deviations from slow-roll inflation.

Abstract

We present constraints on how far single field inflation may depart from the familiar slow-roll paradigm. Considering a fast-roll regime while requiring a (near)-scale-invariant power spectrum introduces large self-interactions for the field and consequently large and scale-dependent non-Gaussianities. Employing this signal, we use the requirement of weak-coupling together with WMAP constraints to derive bounds on generic $P(X,\phi)$ theories of single field inflation.