  Motivated by a semi-holographic approach to the dynamics of quark-gluon
plasma which combines holographic and perturbative descriptions of a strongly
coupled infrared and a more weakly coupled ultraviolet sector, we construct a
hybrid two-fluid model where interactions between its two sectors are encoded
by their effective metric backgrounds, which are determined mutually by their
energy-momentum tensors. We derive the most general consistent ultralocal
interactions such that the full system has a total conserved energy-momentum
tensor in flat Minkowski space and study its consequences in and near thermal
equilibrium by working out its phase structure and its hydrodynamic modes.
