A Panorama of Viable $F(R)$ Gravity Dark Energy Models

TL;DR

This paper explores various $F(R)$ gravity models that unify inflation and dark energy, demonstrating their late-time dynamics, viability with Planck data, and the diverse dark energy behaviors they can produce.

Contribution

It provides a numerical analysis of $F(R)$ models that are viable, compatible with observations, and capable of generating a wide range of dark energy phenomena.

Findings

Models exhibit dark energy oscillations.

Models unify inflation and dark energy.

Diverse dark energy behaviors are generated.

Abstract

In this work we shall study the late-time dynamics of several $F(R)$ gravity models. By appropriately expressing the field equations in terms of the redshift and of a statefinder function, we shall solve numerically the field equations using appropriate physical motivated initial conditions. We consider models which, by construction, are described by a nearly $R^2$-model at early epochs and we fine tune the parameters to achieve viability and compatibility with the latest Planck constraints at late times. Such models provide a unified description of inflation and dark energy era and notably a common feature of all the models is the presence of dark energy oscillations. Furthermore, we show that, in contrast to general relativistic fluids and scalar field descriptions, a large spectrum of different dark energy physics is generated by simple $F(R)$ gravity models, varying from phantom, to nearly de Sitter and to quintessential dark energy eras.