Towards testing the general bounce cosmology with the CMB B-mode auto-bispectrum

Abstract

It has been shown that a three-point correlation function of tensor perturbations from a bounce model in general relativity with a minimally-coupled scalar field is highly suppressed, and the resultant three-point function of cosmic microwave background (CMB) B-mode polarizations is too small to be detected by CMB experiments. On the other hand, bounce models in a more general class with a non-minimal derivative coupling between a scalar field and gravity can predict the three-point correlation function of the tensor perturbations without any suppression, the amplitude of which is allowed to be much larger than that in general relativity. In this paper, we evaluate the three-point function of the B-mode polarizations from the general bounce cosmology with the non-minimal coupling and show that a signal-to-noise ratio of the B-mode auto-bispectrum in the general class can reach unity for $\ell_{\rm max}\geq9$ and increase up to $5.39$ for $\ell_{\rm max}=100$ in the full-sky case. We also discuss the possibility to test the general class of bounce models by upcoming CMB experiments.