Holographic dark energy interacting with dark matter
  We investigate a spatially flat Friedmann-Robertson-Walker (FRW) cosmological
model with cold dark matter coupled to a dark energy which is given by the
modified holographic Ricci cutoff. The interaction used is linear in both dark
energy densities, the total energy density and its derivative. Using the
statistical method of $\chi^2$-function for the Hubble data, we obtain
$H_0=73.6km/sMpc$, $\omega_s=\gamma_s -1=-0.842$ 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 $0.25R < \ro_x < 0.27R$.
