Higher order statistics of curvature perturbations in IFF model and its Planck constraints

TL;DR

This paper analyzes the higher order statistics of curvature perturbations generated during inflation in the IFF model, using Planck data to constrain the model's parameters and exploring the relationship between non-linear parameters.

Contribution

It provides a comprehensive constraint analysis of the IFF inflation model based on Planck observations of power spectrum and non-Gaussianity parameters, revealing a link between f_nl and au_nl.

Findings

au_nl constraints are most stringent when P_ observed by Planck.

A general relationship between f_nl and au_nl is established.

Detectable au_nl can be produced even if f_nl is of order 1.

Abstract

We compute the power spectrum P_\zeta, and non-linear parameters f_nl and \tau_nl of the curvature perturbation induced during inflation by the electromagnetic fields in the kinetic coupling model (IFF model). By using the observational result of P_\zeta, f_nl and \tau_nl reported by the Planck collaboration, we study the constraint on the model comprehensively. Interestingly, if the single slow-rolling inflaton is responsible for the observed P_\zeta, the constraint from \tau_nl is most stringent. We also find a general relationship between f_nl and \tau_nl generated in this model. Even if f_nl \sim O(1), a detectable \tau_nl can be produced.