Coincidence problem within dark energy as a coupled self-interacting   Bose-Einstein gas
  A late accelerated expansion of the Universe is obtained from non-relativistic particles with a short-range attractive interaction, and low enough temperature to produce a Bose-Einstein condensate; by considering coupled dark-energy particles, energy is interchanged with dark matter, allowing it to describe recent acceleration by strengthening its effect. We show that for a sizable range of parameters, dark energy and dark matter evolve with similar energy densities, solving the coincidence problem, and in agreement with the luminosity distance vs redshift, derived from supernova data. 
Jaime Besprosvany, German Izquierdo
astro-ph.CO