Large non-Gaussianities with Intermediate Shapes from Quasi-Single Field Inflation

TL;DR

This paper explores slow-roll inflation models with orthogonal fields, revealing large non-Gaussianities with unique shapes that interpolate between known types, due to isocurvature to curvature mode conversion.

Contribution

It introduces a new class of non-Gaussian shapes in quasi-single field inflation, expanding understanding of possible inflationary signatures.

Findings

Large bispectra with novel intermediate shapes

Non-Gaussianities differ from simple isocurvature projections

Shapes interpolate between equilateral and local types

Abstract

We study the slow-roll inflation models, where the inflaton slow-rolls along a trajectory whose orthogonal directions are lifted by potentials with masses of order the Hubble parameter. In these models large non-Gaussianities can be generated through the transformation from the isocurvature modes to the curvature mode, once the inflaton trajectory turns. We find large bispectra with one-parameter family of novel shapes, interpolating between the equilateral and local shape. According to the in-in formalism, the shapes of these non-Gaussianities are different from a simple projection from the isocurvature non-Gaussian correlation functions.