Cosmic Acceleration from Elementary Interactions
  It is possible to generate an accelerated period of expansion from reasonable potentials acting between the universe particle constituents. The pressure of primordial nucleons interacting via a simple nuclear potential is obtained via Mayer's cluster expansion technique. The attractive part of the potential engenders a negative pressure and may therefore be responsible for the cosmic acceleration. 
R. Aldrovandi, R. R. Cuzinatto and L. G. Medeiros