Interacting holographic dark energy models: A general approach
  Dark energy models inspired by the cosmological holographic principle are
studied in homogeneous isotropic spacetime with a general choice for the dark
energy density $\rho_d=3(\alpha H^2+\beta\dot{H})$. Special choices of the
parameters enable us to obtain three different holographic models, including
the holographic Ricci dark energy(RDE) model. Effect of interaction between
dark matter and dark energy on the dynamics of those models are investigated
for different popular forms of interaction. It is found that crossing of
phantom divide can be avoided in RDE models for $\beta>0.5$ irrespective of the
presence of interaction. A choice of $\alpha=1$ and $\beta=2/3$ leads to a
varying $\Lambda$-like model introducing an IR cutoff length $\Lambda^{-1/2}$.
It is concluded that among the popular choices an interaction of the form
$Q\propto H\rho_m$ suits the best in avoiding the coincidence problem in this
model.
