Disformal Theories of Gravity: From the Solar System to Cosmology

Understand

This paper is concerned with theories of gravity that contain a scalar coupled both conformally and disformally to matter through the metric.

• By systematically deriving the non-relativistic limit, it is shown that no new non-linear screening mechanisms are present beyond the Vainshtein mechanism and chameleon-like screening.
• If one includes the cosmological expansion of the universe, disformal effects that are usually taken to be absent can be present in the solar system.
• When the conformal factor is absent, fifth-forces can be screened on all scales when the cosmological field is slowly-rolling.