  We study interacting scalar field theory non-minimally coupled to gravity in
the FRW background. We show that for a specific choice of interaction terms,
the energy-momentum tensor of the scalar field vanishes, and as a result the
scalar field does not gravitate. The naive space dependent solution to
equations of motion gives rise to singular field profile. We carefully analyze
the energy-momentum tensor for such a solution and show that the singularity of
the solution gives a subtle contribution to the energy-momentum tensor. The
space dependent solution therefore is not non-gravitating. Our conclusion is
applicable to other space-time dependent non-gravitating solutions as well. We
study hybrid inflation scenario in this model when purely time dependent
non-gravitating field is coupled to another scalar field.
