Large Local Non-Gaussianity from General Single-field Inflation

TL;DR

This paper explores non-Gaussian features in ultra slow-roll inflation, demonstrating that local non-Gaussianity predictions are robust under general initial conditions and saturate the Suyama-Yamaguchi relation.

Contribution

It provides a comprehensive calculation of bispectrum and trispectrum in ultra slow-roll inflation with general initial states, confirming the robustness of local non-Gaussianity predictions.

Findings

Trispectrum is of local shape.

Local non-Gaussianity prediction is robust.

Suyama-Yamaguchi relation is saturated.

Abstract

We investigate the non-Gaussian signatures of ultra slow-roll inflation. The bispectrum and the trispectrum are calculated with general initial conditions. The trispectrum is of local shape, as in the case of the bispectrum. We show that the prediction of local non-Gaussianity is robust again generalizing the Bunch-Davies vacuum. The Suyama-Yamaguchi relation is saturated in this scenario.