Irrotational-fluid cosmologies in fourth-order gravity

TL;DR

This paper investigates specific irrotational-fluid cosmological models within f(R)-gravity, aiming to identify restrictions on the gravitational Lagrangian and analyze model consistency under various conditions.

Contribution

It introduces new classes of irrotational-fluid cosmologies in f(R)-gravity and examines their mathematical and physical consistency.

Findings

Linearised dust models are consistent in shear-free cases.

Certain irrotational spacetimes can exist non-expanding in f(R)-gravity.

Conditions for vanishing Weyl tensor components are analyzed.

Abstract

In this paper, we explore classes of irrotational-fluid cosmological models in the context of f(R)-gravity in an attempt to put some theoretical and mathematical restrictions on the form of the f(R) gravitational Lagrangian. In particular, we investigate the consistency of linearised dust models for shear-free cases as well as in the limiting cases when either the gravito-magnetic or gravito-elecric components of the Weyl tensor vanish. We also discuss the existence and consistency of classes of non-expanding irrotational spacetimes in f(R)-gravity.