TAPIR Seminar
I will review the assumptions behind the standard cosmological model and two distinct ways to produce alternatives in which there is no cosmological constant. The first possibility is to keep standard gravity but accept an inhomogeneous metric: such a universe is able to reproduce supernova or Baryon Acoustic Oscillation scale observations, but not both simultaneously. The second is to keep the large scale homogeneity of the metric, while allowing a theory of gravity different from Einstein's. I will present some recent progress in the understanding of scalar-tensor theories, focusing on the identification of the most general class of viable theories and the possibility of them producing distinctive cosmological signatures while remaining compatible with local gravity tests.