Holographic Dark Energy in Braneworld Models with Moving Branes and the w=-1 Crossing

TL;DR

This paper investigates holographic dark energy in 5D braneworld models with moving branes, showing it can naturally cross the phantom divide and match observational data without extra fields, given certain fine-tuning.

Contribution

It demonstrates that holographic dark energy in moving-brane models can naturally exhibit w=-1 crossing behavior without additional fields, under specific fine-tuning.

Findings

wΛ was greater than -1 in the past

Current wΛ is approximately -1.05

wΛ crosses -1 at redshift z≈0.41

Abstract

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 $w_{\Lambda_0}\approx-1.05$, and the phantom bound $w_\Lambda=-1$ was crossed at $z_{p}\approx0.41$, 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.