Dark energy, inflation and dark matter from modified F(R) gravity

TL;DR

This paper reviews how modified F(R) gravity can unify cosmic inflation, dark energy, and dark matter, satisfying local tests and avoiding instabilities, thus serving as a comprehensive cosmological model.

Contribution

It demonstrates that F(R) gravity can simultaneously explain inflation, late-time acceleration, and dark matter within a single framework, ensuring stability and compliance with local gravity tests.

Findings

F(R) models can reproduce the entire universe expansion history.

Certain F(R) models respect Newton's law and avoid matter instability.

The same models can account for dark matter via scalar degrees of freedom.

Abstract

We review modified $F(R)$ gravity as realistic candidate to describe the observable universe expansion history. We show that recent cosmic acceleration, radiation/matter-dominated epoch and inflation could be realized in the framework of $F(R)$-gravity in the unified way. For some viable classes of $F(R)$-gravity, the Newton law is respected and there is no so-called matter instability (the very heavy positive mass for additional scalar degree of freedom is generated). The reconstruction program in modified gravity is also reviewed and it is demonstrated that {\it any} time-evolution of the universe expansion could be realized in $F(R)$-gravity. These models remain to be realistic also in the presence of non-minimal gravitational coupling with usual matter. It is shown that same model which passes local tests and predicts the unification of inflation with cosmic acceleration also describes dark matter thanks to presence of additional scalar degree of freedom and chameleon mechanism.