Holographic Ricci dark energy in Randall-Sundrum braneworld: Avoidance
  of big rip and steady state future
  In the holographic Ricci dark energy (RDE) model, the parameter $\alpha$
plays an important role in determining the evolutionary behavior of the dark
energy. When $\alpha<1/2$, the RDE will exhibit a quintom feature, i.e., the
equation of state of dark energy will evolve across the cosmological constant
boundary $w=-1$. Observations show that the parameter $\alpha$ is indeed
smaller than 1/2, so the late-time evolution of RDE will be really like a
phantom energy. Therefore, it seems that the big rip is inevitable in this
model. On the other hand, the big rip is actually inconsistent with the
theoretical framework of the holographic model of dark energy. To avoid the big
rip, we appeal to the extra dimension physics. In this Letter, we investigate
the cosmological evolution of the RDE in the braneworld cosmology. It is of
interest to find that for the far future evolution of RDE in a Randall-Sundrum
braneworld, there is an attractor solution where the steady state (de Sitter)
finale occurs, in stead of the big rip.
