Resonant Non-Gaussianity

TL;DR

This paper derives the primordial bispectrum for inflation models with sinusoidal potential modulations, revealing a resonant non-Gaussianity shape distinct from common templates, useful for observational constraints.

Contribution

It provides an analytical derivation of resonant non-Gaussianity shape from first principles in modulated inflation models, highlighting its unique features.

Findings

Resonance causes large non-Gaussian signals.

Resonant shape is distinct from local, equilateral, orthogonal shapes.

Analytic expression aids observational constraints.

Abstract

We provide a derivation from first principles of the primordial bispectrum of scalar perturbations produced during inflation driven by a canonically normalized scalar field whose potential exhibits small sinusoidal modulations. A potential of this type has been derived in a class of string theory models of inflation based on axion monodromy. We use this model as a concrete example, but we present our derivations and results for a general slow-roll potential with superimposed modulations. We show analytically that a resonance between the oscillations of the background and the oscillations of the fluctuations is responsible for the production of an observably large non-Gaussian signal. We provide an explicit expression for the shape of this resonant non-Gaussianity. We show that there is essentially no overlap between this shape and the local, equilateral, and orthogonal shapes, and we stress that resonant non-Gaussianity is not captured by the simplest version of the effective field theory of inflation. We hope our analytic expression will be useful to further observationally constrain this class of models.