Neutrinos in the holographic dark energy model: constraints from latest measurements of expansion history and growth of structure

TL;DR

This paper investigates holographic dark energy models with massive neutrinos and dark radiation, analyzing their effects on cosmic structure and constraining parameters using the latest observational data.

Contribution

It introduces a detailed analysis of HDE models with neutrinos/dark radiation, employing the PPF approach to handle perturbations across the phantom divide.

Findings

Sum of neutrino masses < 0.186 eV (95% CL)

Effective number of neutrino species N_eff ≈ 3.75

Constraints consistent with current cosmological observations

Abstract

The model of holographic dark energy (HDE) with massive neutrinos and/or dark radiation is investigated in detail. The background and perturbation evolutions in the HDE model are calculated. We employ the PPF approach to overcome the gravity instability difficulty (perturbation divergence of dark energy) led by the equation-of-state parameter $w$ evolving across the phantom divide $w=-1$ in the HDE model with $c<1$. We thus derive the evolutions of density perturbations of various components and metric fluctuations in the HDE model. The impacts of massive neutrino and dark radiation on the CMB anisotropy power spectrum and the matter power spectrum in the HDE scenario are discussed. Furthermore, we constrain the models of HDE with massive neutrinos and/or dark radiation by using the latest measurements of expansion history and growth of structure, including the Planck CMB temperature data, the baryon acoustic oscillation data, the JLA supernova data, the Hubble constant direct measurement, the cosmic shear data of weak lensing, the Planck CMB lensing data, and the redshift space distortions data. We find that $\sum m_\nu<0.186$ eV (95\% CL) and $N_{\rm eff}=3.75^{+0.28}_{-0.32}$ in the HDE model from the constraints of these data.