Fermi-bounce cosmology and the fermion curvaton mechanism

TL;DR

This paper proposes a nonsingular bouncing cosmology using fermion fields with BCS condensation, introducing a fermion curvaton mechanism to produce a nearly scale-invariant CMB spectrum and satisfy recent observations.

Contribution

It introduces a novel fermion curvaton mechanism in bouncing cosmology, explaining the CMB spectrum without singularities and addressing anisotropic stress issues.

Findings

Successfully dilutes anisotropic stress near the bounce

Achieves nearly scale-invariant CMB spectrum

Aligns with latest cosmological observations

Abstract

A nonsingular bouncing cosmology can be achieved by introducing a fermion field with BCS condensation occurring at high energy scales. In this paper we are able to dilute the anisotropic stress near the bounce by means of releasing the gap energy density near the phase transition between the radiation and condensate states. In order to explain the nearly scale-invariant CMB spectrum, another fermion field is required. We investigate one possible curvaton mechanism by involving one another fermion field without condensation where the mass is lighter than the background field. We show that, by virtue of the fermion curvaton mechanism, our model can satisfy the latest cosmological observations very well, and that the fermion species involved may realize a cosmological see-saw mechanism after one finely tunes model parameters.