Primordial non-Gaussianities of scalar and tensor perturbations in general bounce cosmology: Evading the no-go theorem

TL;DR

This paper demonstrates that in general scalar-tensor theories, it is possible to evade previous no-go theorems regarding matter bounce cosmology, allowing compatibility with observational bounds on non-Gaussianity and tensor-to-scalar ratio.

Contribution

It extends the analysis of bounce cosmology by evaluating perturbation spectra within Horndeski theories, showing potential to satisfy observational constraints.

Findings

Scalar and tensor spectra computed in Horndeski theory.

Non-Gaussian signatures can distinguish bounce models from inflation.

Evades previous no-go theorem constraints.

Abstract

It has been pointed out that matter bounce cosmology driven by a k-essence field cannot satisfy simultaneously the observational bounds on the tensor-to-scalar ratio and non-Gaussianity of the curvature perturbation. In this paper, we show that this is not the case in more general scalar-tensor theories. To do so, we evaluate the power spectra and the bispectra of scalar and tensor perturbations on a general contracting background in the Horndeski theory. We then discuss how one can discriminate contracting models from inflation based on non-Gaussian signatures of tensor perturbations.