Screening Modifications of Gravity through Disformally Coupled Fields

TL;DR

This paper explores a disformal scalar field coupling in modified gravity theories, which can evade local tests and drive cosmic acceleration, with observable effects on large-scale structure formation.

Contribution

It introduces a disformal screening mechanism that allows strongly coupled scalar fields to be consistent with local gravity tests and explains cosmic acceleration.

Findings

Disformal coupling can hide scalar fields in the solar system.

The model fits cosmological observational data well.

Large-scale structure formation shows signatures of disformal interactions.

Abstract

It is shown that extensions to General Relativity, which introduce a strongly coupled scalar field, can be viable if the interaction has a non-conformal form. Such disformal coupling depends upon the gradients of the scalar field. Thus, if the field is locally static and smooth, the coupling becomes invisible in the solar system: this is the disformal screening mechanism. A cosmological model is considered where the disformal coupling triggers the onset of accelerated expansion after a scaling matter era, giving a good fit to a wide range of observational data. Moreover, the interaction leaves signatures in the formation of large-scale structure that can be used to probe such couplings.