Cosmological evolution, future singularities, Little Rip and Pseudo-Rip in viable f(R) theories and their scalar-tensor counterpart

TL;DR

This paper analyzes viable f(R) gravity models for dark energy, exploring their cosmological evolution, stability, and potential future singularities like Little Rip and Pseudo-Rip, including their scalar-tensor counterparts.

Contribution

It provides a detailed analysis of cosmological evolution in viable f(R) models, including stability and future singularity scenarios, and examines their scalar-tensor equivalence.

Findings

Cosmological evolution can enter a phantom phase but remains asymptotically stable.

Viable f(R) models can reproduce late-time acceleration consistent with observations.

Future singularities like Little Rip and Pseudo-Rip are possible within these models.

Abstract

Modified f(R) gravity is one of the most promising candidates for dark energy, and even for the unification of the whole cosmological evolution, including the inflationary phase. Within this class of theories, the so-called viable modified gravities represent realistic theories that are capable of reproducing late-time acceleration, and satisfy strong constraints at local scales, where General Relativity is recovered. The present manuscript deals with the analysis of the cosmological evolution for some of these models, which indicates that the evolution may enter into a phantom phase, but the behavior may be asymptotically stable. Furthermore, the scalar-tensor equivalence of f(R) gravity is considered, which provides useful information about the possibility of the occurrence of a future singularity. The so-called Little Rip and Pseudo-Rip are also studied in the framework of this class of modified gravities.