CMB and BAO constraints for an induced gravity dark energy model with a quartic potential

We study the predictions for structure formation in an induced gravity dark energy model with a quartic potential. By developing a dedicated Einstein-Boltzmann code, we study self-consistently the dynamics of homogeneous cosmology and of linear perturbations without using any parametrization. By evolving linear perturbations with initial conditions in the radiation era, we accurately recover the quasi-static analytic approximation in the matter dominated era. We use PLANCK 2013 data and a compilation of baryonic acoustic oscillation (BAO) data to constrain the coupling gamma to the Ricci curvature and the other cosmological parameters. By connecting the gravitational constant in the Einstein equation to the one measured in a Cavendish-like experiment, we find gamma < 0 : 0012 at 95% CL with PLANCK 2013 and BAO data. This is the tightest cosmological constraint on gamma and on the corresponding derived post-Newtonian parameters. Because of a degeneracy between gamma and the Hubble constant H-0, we show how larger values for gamma are allowed, but not preferred at a significant statistical level, when local measurements of H-0 are combined in the analysis with PLANCK 2013 data.