Dynamical Relaxation of the Dark Matter to Baryon Ratio
  A scalar field interacting differently with dark matter and baryons may explain why their ratio is of order unity today. We provide three working examples, checking them against the observations of CMB, Large Scale Structure, supernovae Ia, and post-newtonian tests of gravity. Such a scenario could make life much easier for supersymmetric dark matter candidates. 
R. Catena, M. Pietroni, and L. Scarabello