Scalar and Tensor Perturbations in DHOST Bounce Cosmology

Understand

We investigate the bounce realization in the framework of DHOST cosmology, focusing on the relation with observables.

• We perform a detailed analysis of the scalar and tensor perturbations during the Ekpyrotic contraction phase, the bounce phase, and the fast-roll expansion phase, calculating the power spectra, the spectral indices, and the tensor to-scalar ratio.
• Furthermore, we study the initial conditions, incorporating perturbations generated by Ekpyrotic vacuum fluctuations, by matter vacuum fluctuations, and by thermal fluctuations.
• The scale invariance of the scalar power spectrum can be acquired by introducing a matter contraction phase before the Ekpyrotic phase or invoking a thermal gas as the source.