Do current cosmological observations rule out all Covariant Galileons?

TL;DR

This study evaluates Covariant Galileon gravity against recent cosmological data, including weak lensing, and finds that these models are statistically incompatible with observations, effectively ruling them out.

Contribution

The paper provides a comprehensive analysis of Covariant Galileon models using the latest data sets and extended cosmological parameters, including neutrino mass hierarchies.

Findings

Covariant Galileon models require non-zero neutrino mass for fit.

Models are statistically ruled out compared to ΛCDM.

No significant difference among neutrino hierarchies.

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 $\Lambda$CDM limit and predict a very different structure formation pattern compared with the standard $\Lambda$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 $\Lambda$CDM one shows that in all the cases considered, Covariant Galileon models are statistically ruled out by cosmological data.