FLRW-Cosmology in Generic Gravity Theories

TL;DR

This paper demonstrates that in FLRW cosmology, the field equations of any generic gravity theory can be expressed as perfect fluid equations, with specific examples including Lovelock and alF(R, \ucalG) theories.

Contribution

It proves a universal property of FLRW cosmology in generic gravity theories, showing their field equations always resemble perfect fluid equations.

Findings

Field equations in FLRW are of perfect fluid type for any generic gravity theory.

Examples include Lovelock and alF(R, alG) theories.

Universal property holds in arbitrary dimensions.

Abstract

We prove that for the Friedmann-Lemaitre-Robertson-Walker metric, the field equations of any generic gravity theory in arbitrary dimensions are of the perfect fluid type. The cases of general Lovelock and $\mathcal{F}(R, \mathcal{G})$ theories are given as examples.