Towards Anisotropy-Free and Non-Singular Bounce Cosmology with Scale-invariant Perturbations

TL;DR

This paper proposes a ghost-free generalized Galileon bounce cosmology that avoids anisotropy and singularities, utilizing a curvaton field to produce scale-invariant perturbations consistent with observations.

Contribution

It introduces a novel bounce model combining Galileon and curvaton fields, addressing anisotropy, singularity, and perturbation generation in a unified framework.

Findings

The model achieves a non-singular bounce free of anisotropy.

It produces nearly scale-invariant perturbations compatible with observations.

The system avoids the Big-Rip after the bounce.

Abstract

We investigate non-singular bounce realizations in the framework of ghost-free generalized Galileon cosmology, which furthermore can be free of the anisotropy problem. Considering an Ekpyrotic-like potential we can obtain a total Equation-of-State (EoS) larger than one in the contracting phase, which is necessary for the evolution to be stable against small anisotropic fluctuations. Since such a large EoS forbids the Galileon field to generate the desired form of perturbations, we additionally introduce the curvaton field which can in general produce the observed nearly scale-invariant spectrum. In particular, we provide approximate analytical and exact semi-analytical expressions under which the bouncing scenario is consistent with observations. Finally, the combined Galileon-curvaton system is free of the Big-Rip after the bounce.