May the Force NOT be with you
Alternative theories of gravity have received considerable attention recently as a possible explanation to cosmic acceleration. If the modification involves a scalar field, such theories introduce an additional Force, whose strength is tightly constrained by local gravity tests. However, these theories might still have a considerable impact on cosmological scales while remaining hidden in the Solar System by means of screening mechanisms. In many cases, these theories are analyzed in a frame in which the scalar couples explicitly to the trace of the energy momentum tensor - a conformal coupling. I will present a generalization of this set-up, based on a disformal coupling to matter, which offers new insights into screening mechanisms, connections between a broader class of scalar-tensor theories of gravity and a variety of phenomenological applications.
References: PRL 109 241102 (1205.3167) and PRD 87 083010 (1210.8016)