The Dark Side and its Nature
  Although the cosmic concordance cosmology is quite successful in fitting data, fine tuning and coincidence problems apparently weaken it. We review several possibilities to ease its problems, by considering various kinds of dynamical Dark Energy and possibly its coupling to Dark Matter, trying to set observational limits on Dark Energy state equation and coupling. 
S.A. Bonometto, R. Mainini, L.P.L. Colombo