Impacts of dark energy on weighing neutrinos: mass hierarchies considered

TL;DR

This study explores how different dark energy models influence constraints on the total neutrino mass using cosmological data, finding that the holographic dark energy model yields the tightest upper limits, nearing the ability to distinguish neutrino mass hierarchies.

Contribution

It provides the most stringent cosmological upper limit on neutrino mass in the holographic dark energy model, approaching the sensitivity needed to differentiate mass hierarchies.

Findings

HDE model yields the tightest neutrino mass constraints.

Upper limit on total neutrino mass is <0.105 eV in HDE model.

Dark energy models significantly affect neutrino mass bounds.

Abstract

Taking into account the mass splittings between three active neutrinos, we investigate impacts of dark energy on constraining the total neutrino mass $\sum m_{\nu}$ by using recent cosmological observations. We consider two typical dark energy models, namely, the $w$CDM model and the holographic dark energy (HDE) model, which both have an additional free parameter compared with the $\Lambda$CDM model. We employ the Planck 2015 data of CMB temperature and polarization anisotropies, combined with low-redshift measurements on BAO distance scales, type Ia supernovae, Hubble constant, and Planck lensing. Compared to the $\Lambda$CDM model, our study shows that the upper limit on $\sum m_{\nu}$ becomes much looser in the $w$CDM model while much tighter in the HDE model. In the HDE model, we obtain the $95\%$ CL upper limit $\sum m_{\nu}<0.105~\textrm{eV}$ for three degenerate neutrinos. This might be the most stringent constraint on $\sum m_{\nu}$ by far and is almost on the verge of diagnosing the neutrino mass hierachies in the HDE model. However, the difference of $\chi^2$ is still not significant enough to distinguish the neutrino mass hierarchies, even though the minimal $\chi^2$ of the normal hierarchy is slightly smaller than that of the inverted hierarchy.