Velocity Curves for Stars in Disk Galaxies: A case for Nearly Newtonian   Dynamics
  The dark matter constraint imposed by the recent WMAP experiment on gravitational theories is analyzed. Using the non-linearity of the vacuum Einstein's equations, it is shown that when the slow motion condition is applied to the geodesic equations, the resulting nearly Newtonian gravitational field describes nearly flat velocity curves for rotating stars in the vicinity of thin disk galaxies. 
M. D. Maia, A. J. S. Capistrano, D.Mulller