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

Understand

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.