Institute for Advanced Study Informal Astrophysics Seminar - CANCELLED

I will present a novel screening mechanism that allows a scalar field to mediate a long range ~Mpc force of gravitational strength in the cosmos while satisfying local tests of gravity. The mechanism hinges on local symmetry restoration in the presence of matter. In regions of sufficiently high matter density, the field is drawn towards phi = 0 where its coupling to matter vanishes and the phi->-phi symmetry is restored. In regions of low density, however, the symmetry is spontaneously broken, and the field couples to matter with gravitational strength. The model predicts deviations from general relativity in the solar system that are within reach of next-generation experiments, as well as astrophysically observable violations of the equivalence principle. The symmetron can be distinguished experimentally from Brans-Dicke gravity, chameleon theories and brane-world modifications of gravity.