Do current cosmological observations rule out all Covariant Galileons?

Abstract

We revisit the cosmology of Covariant Galileon gravity in view of the most recent cosmological data sets, including weak lensing. As a higher derivative theory, Covariant Galileon models do not have a $Λ$CDM limit and predict a very different structure formation pattern compared with the standard $Λ$CDM scenario. Previous cosmological analyses suggest that this model is marginally disfavoured, yet can not be completely ruled out. In this work we use a more recent and extended combination of data, and we allow for more freedom in the cosmology, by including a massive neutrino sector with three different mass hierarchies. We use the Planck measurements of Cosmic Microwave Background temperature and polarization; Baryonic Acoustic Oscillations measurements by BOSS DR12; local measurements of $H_0$; the joint light-curve analysis supernovae sample; and, for the first time, weak gravitational lensing from the KiDS collaboration. We find, that in order to provide a reasonable fit, a non-zero neutrino mass is indeed necessary, but we do not report any sizable difference among the three neutrino hierarchies. Finally, the comparison of the Bayesian Evidence to the $Λ$CDM one shows that in all the cases considered, Covariant Galileon models are statistically ruled out by cosmological data.

8 pages, 5 figures, 2 tables. The Covariant Galileon patch of EFTCAMB is released in the EFTCAMB developers version - accepted version by PRD