Hydrodynamical limit of non-minimally coupled scalar fields

Abstract

In this paper we study how the addition of a non-minimal derivative coupling modifies the energy-momentum tensor of conformally invariant scalar fields in a at Robertson-Walker spacetime. We argue that the resulting energy-momentum tensor is not that of a perfect uid with pressure proportional to density. This suggests that the departure from the cosmological fluid behaviour is a general feature of non-minimally coupled massless scalar fields