title: Testing for w < -1 in the solar system.
abstract: In scalar-tensor theories of gravity, the equation of state of dark energy, w, can become smaller than -1 without violating any energy condition. The value of w today is tied to the level of deviations from general relativity which, in turn, is constrained by solar system and pulsars timing experiments. The conditions on these local constraints for w to be significantly less than -1 are established. It is demonstrated that this requires us to consider theories that differ from the Jordan-Fierz-Brans-Dicke theory and that involve either a steep coupling function or a steep potential. It is also shown how a robust measurement of w could probe scalar-tensor theories.
authors.affiliation: Institut d'Astrophysique de Paris, GReCO-CNRS, UMR 7095, Université Pierre et Marie Curie, 98bis boulevard Arago, 75014 Paris, France. jmartin@iap.fr
authors.forename: Jérôme
authors.initials: J
authors.lastname: Martin
authors.forename: Carlo
authors.initials: C
authors.lastname: Schimd
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Uzan