Bounce and cyclic cosmology in weakly broken galileon theories

TL;DR

This paper explores bounce and cyclic cosmologies within weakly broken galileon theories, analyzing background solutions and perturbations to understand observable implications like spectral indices and tensor-to-scalar ratios.

Contribution

It provides analytical methods to reconstruct potentials and galileon functions for bouncing cosmologies and investigates perturbation effects on observable parameters.

Findings

Analytical expressions for bounce conditions.

Large tensor-to-scalar ratio in the model.

Introduction of a light scalar reduces tensor-to-scalar ratio.

Abstract

We investigate the bounce and cyclicity realization in the framework of weakly broken galileon theories. We study bouncing and cyclic solutions at the background level, reconstructing the potential and the galileon functions that can give rise to a given scale factor, and presenting analytical expressions for the bounce requirements. We proceed to a detailed investigation of the perturbations, which after crossing the bouncing point give rise to various observables, such as the scalar and tensor spectral indices and the tensor-to-scalar ratio. Although the scenario at hand shares the disadvantage of all bouncing models, namely that it provides a large tensor-to-scalar ratio, introducing an additional light scalar significantly reduces it through the kinetic amplification of the isocurvature fluctuations.