Cosmological constraints on induced gravity dark energy models

TL;DR

This paper investigates induced gravity dark energy models with monomial potentials, using recent cosmological data to constrain the coupling to Ricci curvature and improve bounds on deviations from standard gravity.

Contribution

It provides new constraints on the coupling parameter in induced gravity dark energy models using Planck and BAO data, highlighting the models' viability and dependence on potential exponent.

Findings

95% CL bound on coupling: γ < 0.0017 with Planck 2015 data

Bound tightened to γ < 0.00075 with additional BAO data

Improved limits compared to previous Planck 2013 results

Abstract

We study induced gravity dark energy models coupled with a simple monomial potential $\propto \sigma^n$ and a positive exponent $n$. These simple potentials lead to viable dark energy models with a weak dependence on the exponent, which characterizes the accelerated expansion of the cosmological model in the asymptotic attractor, when ordinary matter becomes negligible. We use recent cosmological data to constrain the coupling $\gamma$ to the Ricci curvature, under the assumptions that the scalar field starts at rest deep in the radiation era and that the gravitational constant in the Einstein equations is compatible with the one measured in a Cavendish-like experiment. By using $Planck$ 2015 data only, we obtain the 95 % CL bound $\gamma < 0.0017$ for $n=4$, which is further tightened to $\gamma < 0.00075$ by adding Baryonic Acoustic Oscillations (BAO) data. This latter bound improves by $\sim 30$ % the limit obtained with the $Planck$ 2013 data and the same compilation of BAO data. We discuss the dependence of the $\gamma$ and $\dot G_N/G_N (z=0)$ on $n$.