Folded Resonant Non-Gaussianity in General Single Field Inflation

TL;DR

This paper calculates a new type of large non-Gaussianity in single field inflation caused by small periodic features, highlighting the combined effects of resonance, non-Bunch-Davies vacuum, and higher derivatives.

Contribution

It introduces a comprehensive analysis of non-Gaussianity from multiple mechanisms in single field inflation with periodic features, including novel folded resonant effects.

Findings

Non-Gaussianity can be significantly enhanced by combined mechanisms.

Distinctive shapes and running in the bispectrum are identified.

Results include leading order bispectra for models with periodic features.

Abstract

We compute a novel type of large non-Gaussianity due to small periodic features in general single field inflationary models. We show that the non-Bunch-Davies vacuum component generated by features, although has a very small amplitude, can have significant impact on the non-Gaussianity. Three mechanisms are turned on simultaneously in such models, namely the resonant effect, non-Bunch-Davies vacuum and higher derivative kinetic terms, resulting in a bispectrum with distinctive shapes and running. The size can be equal to or larger than that previously found in each single mechanism. Our full results, including the resonant and folded resonant non-Gaussianities, give the leading order bispectra due to general periodic features in general single field inflation.