f(R) gravity: successes and challenges

TL;DR

This paper reviews f(R) gravity theories as alternatives to dark energy, discussing their successes and the challenges they face in meeting viability criteria.

Contribution

It provides a comprehensive overview of the current status, successes, and challenges of f(R) gravity models in explaining cosmic acceleration.

Findings

f(R) gravity can explain cosmic acceleration without dark energy

Certain formulations of f(R) gravity meet viability criteria

Challenges include stability and consistency with observations

Abstract

We review the state of the art of f(R) theories of gravity (in their various formulations), which have been proposed as an explanation of the cosmic acceleration alternative to dark energy. The successes of f(R) gravity are discussed, together with the challenges imposed by minimal criteria for their viability.