Emergent modified gravity

Abstract

A complete canonical formulation of general covariance makes it possible to
 construct new modified theories of gravity that are not of higher-curvature
 form, as shown here in a spherically symmetric setting. The usual uniqueness
 theorems are evaded by using a crucial and novel ingredient, allowing for
 fundamental fields of gravity distinct from an emergent space-time metric
 that provides a geometrical structure to all solutions. As specific
 examples, there are new expansion-shear couplings in cosmological models, a
 form of modified Newtonian dynamics (MOND) can appear in a space-time
 covariant theory without introducing extra fields, and related effects help
 to make effective models of canonical quantum gravity fully consistent with
 general covariance.