Holographic Dark Energy in Braneworld Models with a Gauss-Bonnet Term in the Bulk. Interacting Behavior and the w =-1 Crossing

TL;DR

This paper explores holographic dark energy within braneworld models incorporating a Gauss-Bonnet term, revealing natural couplings and a dynamic crossing of the phantom divide, with implications for late-time cosmic acceleration.

Contribution

It derives the Friedmann equation in a braneworld with Gauss-Bonnet term and shows the holographic dark energy naturally exhibits quintom behavior crossing w=-1.

Findings

Effective dark energy crosses w=-1 during evolution.

Gauss-Bonnet term lowers current w value.

Gauss-Bonnet term increases the rate of w(z) growth.

Abstract

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 $w=-1$ during the evolution. In particular, the Gauss-Bonnet contribution decreases the present value of $w_\Lambda$, while it increases the growing rate of $w_\Lambda(z)$ with $z$, in comparison with the case where such a term is absent.