Covariant renormalizable gravity and its FRW cosmology

TL;DR

This paper explores a diffeomorphism invariant gravity theory coupled with an ideal fluid, revealing potential super-renormalizability and unique cosmological behaviors differing from General Relativity, including possible inflationary stages.

Contribution

It introduces a non-standard coupling in covariant gravity that breaks Lorentz invariance of the graviton propagator, leading to potential super-renormalizability and novel FRW cosmology.

Findings

Some versions are super-renormalizable with only physical transverse modes.

The FRW cosmology can differ from General Relativity, showing possible quintessence/phantom-like inflation.

Lorentz invariance of the graviton propagator is broken due to non-standard coupling.

Abstract

We consider the diffeomorphism invariant gravity coupled with the ideal fluid in the non-standard way. The Lorentz-invariance of the graviton propagator in such a theory considered as perturbation over flat background turns out to be broken due to non-standard coupling with the ideal fluid. As a result the behavior of the propagator in the ultraviolet/infrared region indicates that some versions of such theory are (super-)renormalizable ones (with appearance of only physical transverse modes). The FRW cosmology in same cases may be different from the one in General Relativity with the possible quintessence/phantom-like inflationary stage.