Generic modification of gravity, late time acceleration and Hubble tension

TL;DR

This paper explores a gravity modification model without extra degrees of freedom, using disformal transformations to achieve late-time acceleration and potentially resolve the Hubble tension.

Contribution

It introduces a generic disformal transformation framework that modifies gravity in the Jordan frame while preserving standard matter conservation and thermal history.

Findings

Late-time acceleration with phantom crossing in the Jordan frame.

Deceleration in the Einstein frame.

Potential resolution of the Hubble tension through phantom phase.

Abstract

We consider a scenario of large-scale modification of gravity that does not invoke extra degrees of freedom but includes coupling between baryonic matter and dark matter in the Einstein frame. The total matter energy density follows the standard conservation, and evolution has the character of deceleration in this frame. The model exhibits interesting features in the Jordan frame realized by virtue of a disformal transformation where individual matter components adhere to standard conservation but gravity is modified. A generic parametrization of disformal transformation leaves thermal history intact. It gives rise to late time acceleration in the Jordan frame, which necessarily includes phantom crossing, which, in the standard framework, can be realized using at least two scalar fields. This scenario is embodied by two distinguishing features, namely, acceleration in the Jordan frame and deceleration in the Einstein frame, and the possibility of resolution of the Hubble tension thanks to the emergence of the phantom phase at late times.