Scale-dependent non-Gaussianity probes inflationary physics

TL;DR

This paper investigates how the scale dependence of non-Gaussianity in primordial density perturbations can reveal details about inflationary physics, introducing new observable parameters and consistency relations.

Contribution

It introduces a framework to characterize the scale dependence of the bispectrum and trispectrum, providing new parameters and relations to distinguish inflation models.

Findings

Scale dependence of non-Gaussianity can be significant in certain inflation scenarios.

New observable parameters help discriminate between different inflation models.

A generalized real-space formulation of curvature perturbation is proposed.

Abstract

We calculate the scale dependence of the bispectrum and trispectrum in (quasi) local models of non-Gaussian primordial density perturbations, and characterize this scale dependence in terms of new observable parameters. They can help to discriminate between models of inflation, since they are sensitive to properties of the inflationary physics that are not probed by the standard observables. We find consistency relations between these parameters in certain classes of models. We apply our results to a scenario of modulated reheating, showing that the scale dependence of non-Gaussianity can be significant. We also discuss the scale dependence of the bispectrum and trispectrum, in cases where one varies the shape as well as the overall scale of the figure under consideration. We conclude providing a formulation of the curvature perturbation in real space, which generalises the standard local form by dropping the assumption that f_NL and g_NL are constants.