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

TL;DR

This paper develops a detailed Einstein-Boltzmann code to analyze structure formation in an induced gravity dark energy model with a quartic potential, constraining the model parameters using Planck 2013 and BAO data.

Contribution

It provides the first self-consistent analysis of linear perturbations in this model without parametrization, deriving tight cosmological constraints on the coupling to Ricci curvature.

Findings

Constraint on coupling parameter γ < 0.0012 at 95% CL

Tightest cosmological bounds on post-Newtonian parameters

Degeneracy between γ and H_0 affects parameter constraints

Abstract

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.