Unification of a Bounce with a Viable Dark Energy Era in Gauss-Bonnet Gravity

TL;DR

This paper demonstrates a unified model in Gauss-Bonnet gravity that describes both a primordial bounce and a viable dark energy era, consistent with observational data and free from oscillations common in other modified gravity theories.

Contribution

It introduces a unified Gauss-Bonnet gravity framework that models both early universe bounce and late-time dark energy, addressing issues like oscillations present in $f(R)$ gravity.

Findings

Primordial bounce with nearly scale-invariant power spectrum

Dark energy era mimics $ m extLambda$CDM and aligns with Planck 2018 data

Dark energy oscillations are absent in the Gauss-Bonnet model but appear in $f(R)$ extensions at $z extasciitilde 4

Abstract

In this work we shall demonstrate that it is possible to describe in a unified way a primordial bounce with the dark energy era, in the context of Gauss-Bonnet modified gravity. Particularly, the early time bounce has a nearly scale invariant power spectrum of primordial scalar curvature perturbations, while the dark energy era is a viable one, meaning that it mimics the $\Lambda$-Cold-Dark-Matter model and also is compatible with the Planck 2018 data on cosmological parameters. In addition, our analysis indicates that the dark energy era is free from dark energy oscillations, which occur in the context of $f(R)$ gravity. We further addressed the later issue by examining $f(R)$ extensions of Gauss-Bonnet models, and we showed that the $f(R)$ gravity part of the action actually produces the dark energy oscillations at redshifts $z\sim 4$.