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 $0.25R < \ro_x < 0.27R$.
