First experimental constraints on the disformally coupled Galileon model

¹ CEA, Centre de Saclay, Irfu/SPP, 91191 Gif-sur-Yvette, France
e-mail: jeremy.neveu@cea.fr
² LPNHE, Université Pierre et Marie Curie, Université Paris Diderot, CNRS-IN2P3, 4 place Jussieu, 75252 Paris Cedex 5, France
³ Center for Astrophysics and Space Astronomy, University of Colorado, Boulder, CO 80309-0389, USA
⁴ Laboratoire de Physique Théorique d’Orsay, Bâtiment 210, Université Paris-Sud 11, 91405 Orsay Cedex, France

Received: 4 March 2014
Accepted: 7 August 2014

Abstract

Aims. The Galileon model is a modified gravity model that can explain the late-time accelerated expansion of the Universe. In a previous work, we derived experimental constraints on the Galileon model with no explicit coupling to matter and showed that this model agrees with the most recent cosmological data. In the context of braneworld constructions or massive gravity, the Galileon model exhibits a disformal coupling to matter, which we study in this paper.

Methods. After comparing our constraints on the uncoupled model with recent studies, we extend the analysis framework to the disformally coupled Galileon model and derive the first experimental constraints on that coupling, using precise measurements of cosmological distances and the growth rate of cosmic structures.

Results. In the uncoupled case, with updated data, we still observe a low tension between the constraints set by growth data and those from distances. In the disformally coupled Galileon model, we obtain better agreement with data and favour a non-zero disformal coupling to matter at the 2.5σ level. This gives an interesting hint of the possible braneworld origin of Galileon theory.