Correlation of isocurvature perturbation and non-Gaussianity

TL;DR

This paper investigates the relationship between primordial non-Gaussianity and isocurvature perturbations, demonstrating how their correlation depends on inflation models and axion parameters through a specific Peccei-Quinn type field model.

Contribution

It provides a detailed analysis of the correlation between bispectrum and cross-correlation power spectrum in models with inflaton and light fields, highlighting the dependence on inflation dynamics.

Findings

Correlation form depends mainly on inflation model

fnl ~ O(1) assumed in analysis

Weak dependence on axion parameters

Abstract

We explore the correlations between primordial non-Gaussianity and isocurvature perturbation. We sketch the generic relation between the bispectrum of the curvature perturbation and the cross-correlation power spectrum in the presence of explicit couplings between the inflaton and another light field which gives rise to isocurvature perturbation. Using a concrete model of a Peccei-Quinn type field with generic gravitational couplings, we illustrate explicitly how the primordial bispectrum correlates with the cross-correlation power spectrum. Assuming the resulting fnl ~ O(1), we find that the form of the correlation depends mostly upon the inflation model but only weakly on the axion parameters, even though fnl itself does depend heavily on the axion parameters.