Exact cosmological solutions of models with an interacting dark sector
  In this work we extend the first order formalism for cosmological models that present an interaction between a fermionic and a scalar field. Cosmological exact solutions describing universes filled with interacting dark energy and dark matter have been obtained. Viable cosmological solutions with an early period of decelerated expansion followed by late acceleration have been found, notably one which presents a dark matter component dominating in the past and a dark energy component dominating in the future. In another one, the dark energy alone is the responsible for both periods, similar to a Chaplygin gas case. Exclusively accelerating solutions have also been obtained. 
A. B. Pavan, Elisa G. M. Ferreira, Sandro M. R. Micheletti, J. C. C.   de Souza and E. Abdalla
gr-qc astro-ph.CO