Non-Gaussianities in New Ekpyrotic Cosmology

TL;DR

New Ekpyrotic Cosmology predicts large, distinguishable non-Gaussian signals in primordial density perturbations, offering a testable alternative to inflationary models with negligible non-Gaussianity.

Contribution

This paper calculates higher-order correlation functions in New Ekpyrotic Cosmology, revealing large non-Gaussianities that differentiate it from inflationary scenarios.

Findings

Large non-Gaussianity signals predicted, just below current CMB sensitivity.

Distinct shape dependence of correlation functions compared to inflation.

Non-Gaussianity serves as a testable signature of the model.

Abstract

New Ekpyrotic Cosmology is an alternative scenario of the early universe which relies on a phase of slow contraction before the big bang. We calculate the 3-point and 4-point correlation functions of primordial density perturbations and find a generically large non-Gaussian signal, just below the current sensitivity level of CMB experiments. This is in contrast with slow-roll inflation, which predicts negligible non-Gaussianity. The model is also distinguishable from alternative inflationary scenarios that yield large non-Gaussianity, such as DBI inflation and the simplest curvaton-like models, through the shape dependence of the correlation functions. Non-Gaussianity therefore provides a distinguishing and testable prediction of New Ekpyrotic Cosmology.