Holographic dark energy in braneworld models with moving branes and the w=-1 crossing

We apply the bulk holographic dark energy in general 5D two-brane models. We extract the Friedmann equation on the physical brane and we show that in the general moving-brane case the effective 4D holographic dark energy behaves as a quintom for a large parameter-space area of a simple solution subclass. We find that w(Lambda) was larger than - 1 in the past while its present value is w(Lambda 0) approximate to - 1.05, and the phantom bound w(Lambda) = - 1 was crossed at z(p) approximate to 0.41, a result in agreement with observations. Such a behavior arises naturally, without the inclusion of special fields or potential terms, but a fine-tuning between the 4D Planck mass and the brane tension has to be imposed.