Bouncing universes and dark energy

Abstract

We consider the possibility of a universe whose dark energy (DE) is made out of a negative cosmological constant Λ and a dynamical component X, dubbed as ”cosmon”, which does not interact with Λ. Due to Λ < 0, the late-time accelerated expansion rate is caused by X. In this paper, the study of this framework has been performed by implementing a piece-wise function for the equation of state (EoS) parameter of the cosmon. This parametrization provides an analysis of the impact on the total DE behaviour when a transition from phantom-like to quintessence cosmon (or vice versa) takes place. It has been found that a stopping point in the Universe is displayed in the future when a transition of X from phantom-like to quintessence occurs. For such transition, the ratio of the DE density to matter density (ρD/ρm) is bounded, giving a possible solution to the cosmological coincidence problem. Furthermore, for a phantom-like cosmon at present, we can obtain values of the Hubble constant (H0) compatible with the ones acquired experimentally for cosmic microwave background data [1] and local data [2].