Generalized Holographic Dark Energy and its Observational Constraints

TL;DR

This paper introduces a generalized holographic dark energy model with a redshift-dependent parameter, deriving its properties and fitting it to observational data, showing it fits better than the original model and allows diverse future behaviors.

Contribution

It proposes a new GHDE model with a variable parameter c(z), derives its analytical properties, and demonstrates improved data fitting and diverse future dark energy behaviors.

Findings

GHDE models fit observational data better than original HDE.

The model allows for quintessence, cosmological constant, or phantom-like future behaviors.

The JBP-type c(z) reduces the chi-squared by 2.16 compared to HDE.

Abstract

In the original holographic dark energy (HDE) model, the dark energy density is proposed to be $\rho_{de} = 3c^2M^2_{pl}L^{-2}$, with $c$ is a dimensionless constant characterizing the properties of the HDE. In this work, we propose the generalized holographic dark energy (GHDE) model by considering the parameter $c$ as a redshift-dependent function $c(z)$. We derive all the physical quantities of the GHDE model analytically, and fit the $c(z)$ by trying four kinds of parametrizations. The cosmological constraints of the $c(z)$ are obtained from the joint analysis of the present SNLS3+BAO+CMB+$H_0$ data. We find that, compared with the original HDE model, the GHDE models can provide a better fit to the data. For example, the GHDE model with JBP-type $c(z)$ can reduce the $\chi^2_{min}$ of the HDE model by 2.16. We also find that, unlike the original HDE model with a phantom-like behavior in the future, the GHDE models can present many more different possibilities, i.e., it allows the GHDE in the future to be either quintessence like, cosmological constant like, or phantom like, depending on the forms of $c(z)$.