Dark Matter and Dark Energy from a single scalar field
  The strong CP problem was solved by Peccei & Quinn by introducing axions, which are a viable candidate for DM. Here the PQ approach is modified so to yield also Dark Energy (DE), which arises in fair proportions, without tuning any extra parameter. DM and DE arise from a single scalar field and, in the present ecpoch, are weakly coupled. Fluctuations have a fair evolution. The model is also fitted to WMAP release, using a MCMC technique, and performs as well as LCDM, coupled or uncoupled Dynamical DE. Best-fit cosmological parameters for different models are mostly within 2-$\sigma$ level. The main peculiarity of the model is to favor high values of the Hubble parameter. 
Roberto Mainini, Loris Colombo, Silvio A. Bonometto (Universita' di   Milano-Bicocca, I.N.F.N sez. di Milano)