Local non-Gaussianities at third order in multifield models and the ekpyrotic trispectrum

TL;DR

This paper derives third-order equations for perturbations in two-field cosmological models and calculates the trispectrum, revealing distinctive observational signatures of non-Gaussianities in ekpyrotic and cyclic scenarios.

Contribution

It introduces a covariant formalism to derive third-order perturbation equations and computes the trispectrum for ekpyrotic and cyclic models, highlighting unique non-Gaussian features.

Findings

Non-linearity parameters $f_{NL}$ and $g_{NL}$ produce distinct observational imprints.

Derived third-order equations for adiabatic and entropy perturbations.

Calculated the trispectrum in ekpyrotic and cyclic models.

Abstract

We explain the motivation and main results of our work in reference arXiv:0906.0530 [hep-th]. Using the covariant formalism, we derive the equations of motion for adiabatic and entropy perturbations at third order in perturbation theory for cosmological models involving two scalar fields, and use these equations to calculate the trispectrum of ekpyrotic and cyclic models. The non-linearity parameters $f_{NL}$ and $g_{NL}$ are found to combine to leave a very distinct observational imprint.