Rastall Cosmology and the \Lambda CDM Model

TL;DR

This paper demonstrates that Rastall's theory with a two-fluid model replicates the DM cosmology at background and linear perturbation levels, but allows for dark energy clustering, potentially enabling observational distinction.

Contribution

It shows that Rastall's theory can reproduce DM behavior with a novel feature of dark energy clustering, offering a new perspective on alternative gravity models.

Findings

Rastall cosmology matches DM at background and linear levels.

Dark energy can cluster in Rastall's theory.

Potential to distinguish models at non-linear perturbative level.

Abstract

Rastall's theory is based on the non-conservation of the energy-momentum tensor. We show that, in this theory, if we introduce a two-fluid model, one component representing vacuum energy whereas the other pressureless matter (e.g. baryons plus cold dark matter), the cosmological scenario is the same as for the \Lambda CDM model, both at background and linear perturbative levels, except for one aspect: now dark energy may cluster. We speculate that this can lead to a possibility of distinguishing the models at the non-linear perturbative level.