Exploring interacting holographic dark energy in a perturbed universe with parameterized post-Friedmann approach

TL;DR

This paper investigates an interacting holographic dark energy model in a perturbed universe using a parameterized post-Friedmann approach, constrained by current observational data including RSD measurements, revealing a preference for interaction.

Contribution

It introduces the first analysis of interacting holographic dark energy in a perturbed universe with a novel perturbation treatment and observational constraints including RSD data.

Findings

Interacting holographic dark energy is favored over non-interacting models.

A positive coupling parameter is detected at 2.95σ significance with RSD data.

The model successfully incorporates perturbations and observational constraints.

Abstract

The model of holographic dark energy in which dark energy interacts with dark matter is investigated in this paper. In particular, we consider the interacting holographic dark energy model in the context of a perturbed universe, which was never investigated in the literature. To avoid the large-scale instability problem in the interacting dark energy cosmology, we employ the generalized version of the parameterized post-Friedmann approach to treat the dark energy perturbations in the model. We use the current observational data to constrain the model. Since the cosmological perturbations are considered in the model, we can then employ the redshift-space distortions (RSD) measurements to constrain the model, in addition to the use of the measurements of expansion history, which was either never done in the literature. We find that, for both the cases with $Q=\beta H\rho_{\rm c}$ and $Q=\beta H_0\rho_{\rm c}$, the interacting holographic dark energy model is more favored by the current data, compared to the holographic dark energy model without interaction. It is also found that, with the help of the RSD data, a positive coupling $\beta$ can be detected at the $2.95\sigma$ statistical significance for the case of $Q=\beta H_0\rho_{\rm c}$.