Hilltop Non-Gaussianity

TL;DR

This paper investigates how non-Gaussianity in curvature perturbations is influenced by a pseudo Nambu-Goldstone boson with a cosine potential, especially when it starts near the potential's top, revealing conditions for enhancement.

Contribution

It analyzes the impact of initial conditions on non-Gaussianity in models with cosine-type potentials, highlighting when non-Gaussianity is enhanced compared to quadratic cases.

Findings

Non-Gaussianity is similar to quadratic potential if the boson accounts for curvature perturbation.

Non-Gaussianity is enhanced when the boson does not account for curvature perturbation.

Initial position near the potential top affects the magnitude of non-Gaussianity.

Abstract

We study non-Gaussianity induced by a pseudo Nambu-Goldstone boson with a cosine-type scalar potential. We focus on how the non-Gaussianity is affected when the pseudo Nambu-Goldstone boson rolls down from near the top of the scalar potential where the deviation from a quadratic potential is large. We find that the resultant non-Gaussianity is similar to that obtained in the quadratic potential, if the pseudo Nambu-Goldstone boson accounts for the curvature perturbation; the non-Gaussianity is enhanced, otherwise.