Holographic dark energy at the Ricci scale
  We consider a holographic cosmological model in which the infrared cutoff is
fixed by the Ricci's length and dark matter and dark energy do not evolve
separately but interact non-gravitationally with one another. This
substantially alleviates the cosmic coincidence problem as the ratio between
both components remains finite throughout the expansion. We constrain the model
with observational data from supernovae, cosmic background radiation, baryon
acoustic oscillations, gas mass fraction in galaxy clusters, the history of the
Hubble function, and the growth function. The model shows consistency with
observation.
