Best values of parameters for interacting HDE with GO IR-cutoff in Brans-Dicke cosmology

TL;DR

This paper explores an interacting holographic dark energy model with GO IR-cutoff in Brans-Dicke cosmology, showing it can alleviate the coincidence problem, cross the phantom divide, and produce a stable dark energy dominated universe consistent with observations.

Contribution

It introduces a novel analysis of HDE with GO cutoff in Brans-Dicke cosmology, demonstrating stability and observational viability unlike in Einstein gravity.

Findings

The model can alleviate the cosmic coincidence problem.

It predicts a transition from deceleration to acceleration at redshift z≥0.5.

The model achieves a stable dark energy dominated universe with specific parameter choices.

Abstract

We investigate the interacting holographic dark energy (HDE) with Granda-Oliveros (GO) IR-cutoff in the framework of Brans-Dicke (BD) cosmology. We obtain the equation of state (EoS) parameter of HDE, $w_D$, the effective EoS parameter $w_{\mathrm{eff}}$, the deceleration parameter $q $ and the squared of sound speed $v_s^2$ in a flat FRW universe. We show that at late time the cosmic coincidence problem can be alleviated. Also we show that for non-interacting case, HDE can give a unified dark matter-dark energy profile in BD cosmology, except that it cannot solve the coincidence problem in the future. By studying the equation of state parameter, we see that the phantom divide may be crossed. Using the latest observational data, we calculate the best values of the parameters for interacting HDE in BD framework. Computing the deceleration parameter implies that the transition from deceleration to the acceleration phase occurred for redshift $z\geq 0.5$. Finally, we investigate the sound stability of the model, and find that HDE with GO cutoff in the framework of BD cosmology can lead to a stable DE-dominated universe favored by observations, provided we take $\beta=0.44$ and $b^2<0.35$. This is in contrast to HDE model in Einstein gravity which does not lead to a stable DE dominated universe.