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Do current cosmological observations rule out all covariant Galileons?

S. Peirone, N. Frusciante, B. Hu, M. Raveri, N. Silvestri

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 ΛCDM limit and predict a very different structure formation pattern compared with the standard ΛCDM scenario. Previous cosmological analyses suggest that this model is marginally disfavored, yet cannot 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 H0; 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 nonzero 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 ΛCDM one shows that in all the cases considered, covariant Galileon models are statistically ruled out by cosmological data.

Keywords
Astrophysics - Cosmology and Nongalactic Astrophysics; General Relativity and Quantum Cosmology

Physical Review D
Volume 97, Issue 6
2018 March

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Instituto de Astrofísica e Ciências do Espaço Universidade do Porto Faculdade de Ciências da Universidade de Lisboa
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia