Observational constraints on the interacting Ricci dark energy model
  We consider an extension of the holographic Ricci dark energy model by
introducing an interaction between dark energy and matter. In this model, the
dark energy density is given by $rho_{Lambda}=-frac{1}{2}alpha M_{p}^{2}{R}$,
where ${R}$ is the Ricci scalar curvature, $M_{p}$ is the reduced Planck mass,
and $alpha$ is a dimensionless parameter. The interaction rate is given by
$Q=gamma H rho_{Lambda}$, where $H$ is the Hubble expansion rate, and $gamma$
is a dimensionless parameter. We investigate current observational constraints
on this model by applying the type Ia supernovae, the baryon acoustic
oscillation and the CMB anisotropy data. It is shown that a nonvanishing
interaction rate is favored by the observations. The best fit values are
$alpha=0.45 pm 0.03$ and $gamma=0.15 pm 0.03$ for the present dark energy
density parameter $Omega_{Lambda 0}=0.73 pm0.03$.
