Holographic dark energy in braneworld models with a Gauss-Bonnet term in the bulk.: Interacting behavior and the ω=-1 crossing

We apply bulk holographic dark energy in general braneworld models with a Gauss-Bonnet term in the bulk and an induced gravity term and a perfect fluid on the brane. Without making any additional assumptions we extract the Friedmann equation on the physical brane and we show that a rho-rho(Lambda) coupling arises naturally by the full 5D dynamics. The low-energy (late-time) evolution reveals that the effective 4D holographic dark energy behaves as "quintom", that is it crosses the phantom divide omega = -1 during the evolution. In particular, the Gauss-Bonnet contribution decreases the present value Of omega(Lambda), while it increases the growing rate Of omega(Lambda) (Z) with z, in comparison with the case where such a term is absent. (C) 2008 Elsevier B.V. All rights reserved.