Holographic dark energy in braneworld models with a Gauss–Bonnet term in the bulk. Interacting behavior and the w=−1w=−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 ρ–ρΛρ–ρΛ 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 w=−1w=−1 during the evolution. In particular, the Gauss–Bonnet contribution decreases the present value of wΛwΛ, while it increases the growing rate of wΛ(z)wΛ(z) with z, in comparison with the case where such a term is absent.