Higgs Mechanism and the Structure of the Energy-Momentum Tensor in   Einstein Gravity and Conformal Gravity
  In the standard treatment of the Einstein gravitational theory the energy-momentum tensor has always been taken to be composed of perfect fluid aggregates of kinematic Newtonian point test particles with fundamental mechanical masses. Moreover, this standard prescription was not revised after the discovery of the mass-generating Higgs mechanism which is known to be present in the elementary particle physics of these self-same sources and which is also required in the conformal invariant gravitational alternative being considered by Mannheim and Kazanas. In this short contribution we show that despite the presence of the Higgs mechanism, the standard geodesic motion and Euler hydrodynamics still obtain in the one-particle sector of the theory even while the overall energy-momentum tensor differs substantially from the conventional kinematic one. 
Philip D. Mannheim (University of Connecticut) and Demosthenes Kazanas   (NASA/Goddard Space Flight Center)