Simultaneous expansion and rotation of shear-free universes in modified gravity

TL;DR

This paper demonstrates that certain modified gravity models allow shear-free universes to simultaneously expand and rotate, challenging traditional cosmological assumptions.

Contribution

It introduces a covariant framework showing that specific $f(R)$ models enable shear-free universes to expand and rotate concurrently.

Findings

Existence of $f(R)$ models with shear-free, rotating, expanding universes

Covariant formulation of these models

Potential implications for cosmological models

Abstract

We show in a fully covariant way that, there exist a class of $f(R)$ models for which a shear-free, almost FLRW universe can expand and rotate at the same time .