Power-law cosmic expansion in f(R) gravity models

TL;DR

This paper demonstrates that in f(R) gravity theories, only R^n models admit power-law cosmological solutions similar to those in General Relativity, limiting the variety of exact solutions available.

Contribution

It identifies the specific form of f(R) gravity that allows power-law solutions, narrowing the scope of exact cosmological models in modified gravity theories.

Findings

Power-law solutions exist only for R^n gravity within f(R) models.

This restriction aligns certain f(R) models with standard cosmological behaviors.

The set of exact solutions in f(R) gravity is significantly constrained.

Abstract

We show that within the class of f(R) gravity theories, FLRW power-law perfect fluid solutions only exist for R^n gravity. This significantly restricts the set of exact cosmological solutions which have similar properties to what is found in standard General Relativity.