Large and strong scale dependent bispectrum in single field inflation from a sharp feature in the mass

TL;DR

This paper investigates a single-field inflation model with a sharp mass feature, deriving analytical expressions for the power spectrum and bispectrum, revealing scale-dependent oscillations and large non-Gaussianities.

Contribution

It provides an analytical approximation for the curvature perturbation mode function and bispectrum in a model with a step in the mass, highlighting new oscillatory bispectrum shapes.

Findings

Power spectrum exhibits damped oscillations after the step.

Bispectrum shows oscillations with a linear growth envelope at small scales.

Large bispectrum amplitude possible depending on parameters.

Abstract

We study an inflationary model driven by a single minimally coupled standard kinetic term scalar field with a step in its mass modeled by an Heaviside step function. We present an analytical approximation for the mode function of the curvature perturbation, obtain the power spectrum analytically and compare it with the numerical result. We show that, after the scale set by the step, the spectrum contains damped oscillations that are well described by our analytical approximation. We also compute the dominant contribution to the bispectrum in the equilateral and the squeezed limits and find new shapes. In the equilateral and squeezed limits the bispectrum oscillates and it has a linear growth envelope towards smaller scales. The bispectrum size can be large depending on the model parameters.