Holographic interacting dark energy in the braneworld cosmology

We investigate a model of brane cosmology to find a unified description of the radiation-matter-dark energy universe. It is of the interacting holographic dark energy with a bulk-holographic matter chi. This is a five-dimensional cold dark matter, which plays a role of radiation on the brane. Using the effective equations of state omega(eff)(Lambda) instead of the native equations of state omega(Lambda), we show that this model cannot accommodate any transition from the dark energy with omega(eff)(Lambda) >= -1 to the phantom regime omega(eff)(Lambda) < -1. Furthermore, the case of interaction between four-dimensional cold dark matter and five-dimensional cold dark matter is considered for completeness. Here we find that the redshift of matter-radiation equality z(eq) is the same order as z(eq)(ob) = 2.4 x 10(4) Omega(m)h(2). Finally, we obtain a general decay rate G which is suitable for describing all interactions.