Tests of Scalar‐Tensor Gravity

The best‐motivated alternatives to general relativity are scalar‐tensor theories, in which the gravitational interaction is mediated by one or several scalar fields together with the usual graviton. The analysis of their various experimental constraints allows us to understand better which features of the models have actually been tested, and to suggest new observations able to discriminate between them. This talk reviews three classes of constraints on such theories, which are qualitatively different from each other: (i) solar‐system experiments; (ii) binary‐pulsar tests and future detections of gravitational waves from inspiralling binaries; and (iii) cosmological observations. While classes (i) and (ii) impose precise bounds respectively on the first and second derivatives of the matter‐scalar coupling function, (iii) a priori allows us to reconstruct the full shapes of the functions of the scalar field defining the theory, but obviously with more uncertainties and/or more theoretical hypotheses needed...