Cosmological constraints on induced gravity dark energy models
  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
$n$.
