Can F(R)-gravity be a viable model: the universal unification scenario for inflation, dark energy and dark matter

TL;DR

This paper reviews the potential of $F(R)$-gravity as a unified framework for explaining inflation, dark energy, and dark matter, emphasizing its viability, stability, and ability to reproduce any cosmic evolution.

Contribution

It demonstrates that $F(R)$-gravity can unify inflation, cosmic acceleration, and dark matter while satisfying local gravity tests and avoiding matter instability.

Findings

$F(R)$-gravity models can reproduce the entire cosmic history.

Certain classes of $F(R)$-gravity have negligible corrections to Newton's law.

The reconstruction program allows any universe expansion history to be realized.

Abstract

We review on the viability of $F(R)$-gravity. 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 classes of $F(R)$-gravity, the correction to the Newton law is extremely small 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. Special attention is paid to modified gravity which unifies inflation with cosmic acceleration and passes local tests. It turns out that such a theory may describe also dark matter.