Holographic dark energy linearly interacting with dark matter
  We investigate a spatially flat Friedmann-Robertson-Walker (FRW) cosmological model with cold dark matter coupled to a modified holographic Ricci dark energy through a general interaction term linear in the energy densities of dark matter and dark energy, the total energy density and its derivative. Using the statistical method of $\chi^2$-function for the Hubble data, we obtain $H_0=73.6$km/sMpc, $\omega_s=-0.842$ for the asymptotic equation of state and $ z_{acc}= 0.89 $. The estimated values of $\Omega_{c0}$ which fulfill the current observational bounds corresponds to a dark energy density varying in the range $0.25R < \ro_x < 0.27R$. 
Luis P. Chimento, M\'onica I. Forte and Mart\'in G. Richarte
gr-qc astro-ph.CO hep-th