Momentum dependence of the bispectrum in two-field inflation

TL;DR

This paper investigates how the bispectrum's non-Gaussianity parameter fNL varies with momentum in two-field inflation models, focusing on scale and shape dependence, and introduces spectral indices to quantify these effects.

Contribution

It introduces two spectral indices to quantify momentum dependence of fNL in two-field inflation and analyzes how scale and shape variations affect non-Gaussianity.

Findings

Identified sources of scale dependence in fNL.

Defined spectral indices for momentum dependence.

Illustrated results with specific inflationary examples.

Abstract

We examine the momentum dependence of the bispectrum of two-field inflationary models within the long-wavelength formalism. We determine the sources of scale dependence in the expression for the parameter of non-Gaussianity fNL and study two types of variation of the momentum triangle: changing its size and changing its shape. We introduce two spectral indices that quantify the possible types of momentum dependence of the local type fNL and illustrate our results with examples.