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Impacts of dark energy on weighing neutrinos: mass hierarchies considered

Sai Wang, Yi-Fan Wang, Dong-Mei Xia, Xin Zhang

TL;DR

The paper investigates how two dynamical dark energy models, $w$CDM and holographic dark energy (HDE), affect cosmological constraints on the total neutrino mass $\sum m_ν$ while incorporating neutrino mass splittings from oscillation data. Using Planck 2015 CMB data combined with low-redshift probes (BAO, SN, $H_0$, and Planck lensing), it shows that $w$CDM generally loosens the bounds on $\sum m_ν$ relative to $Λ$CDM, whereas HDE tightens them, with the strongest bound $\sum m_ν<0.105$ eV achieved for the DH case in HDE. Including low-redshift data further stabilizes ΛCDM and HDE constraints but does not decisively distinguish neutrino hierarchies; NH is slightly favored by $\chi^2$ but the difference is not statistically significant. The results suggest that cosmology with non-Λ dark energy could approach discriminating neutrino mass hierarchies, though more data are needed for a decisive determination.

Abstract

Taking into account the mass splittings between three active neutrinos, we investigate impacts of dark energy on constraining the total neutrino mass $\sum m_ν$ 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 $Λ$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 $Λ$CDM model, our study shows that the upper limit on $\sum m_ν$ 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 $\sum m_ν<0.105~\textrm{eV}$ for three degenerate neutrinos. This might be the most stringent constraint on $\sum m_ν$ by far and is almost on the verge of diagnosing the neutrino mass hierachies in the HDE model. However, the difference of $χ^2$ is still not significant enough to distinguish the neutrino mass hierarchies, even though the minimal $χ^2$ of the normal hierarchy is slightly smaller than that of the inverted hierarchy.

Impacts of dark energy on weighing neutrinos: mass hierarchies considered

TL;DR

The paper investigates how two dynamical dark energy models, CDM and holographic dark energy (HDE), affect cosmological constraints on the total neutrino mass while incorporating neutrino mass splittings from oscillation data. Using Planck 2015 CMB data combined with low-redshift probes (BAO, SN, , and Planck lensing), it shows that CDM generally loosens the bounds on relative to CDM, whereas HDE tightens them, with the strongest bound eV achieved for the DH case in HDE. Including low-redshift data further stabilizes ΛCDM and HDE constraints but does not decisively distinguish neutrino hierarchies; NH is slightly favored by but the difference is not statistically significant. The results suggest that cosmology with non-Λ dark energy could approach discriminating neutrino mass hierarchies, though more data are needed for a decisive determination.

Abstract

Taking into account the mass splittings between three active neutrinos, we investigate impacts of dark energy on constraining the total neutrino mass by using recent cosmological observations. We consider two typical dark energy models, namely, the CDM model and the holographic dark energy (HDE) model, which both have an additional free parameter compared with the 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 CDM model, our study shows that the upper limit on becomes much looser in the CDM model while much tighter in the HDE model. In the HDE model, we obtain the CL upper limit for three degenerate neutrinos. This might be the most stringent constraint on by far and is almost on the verge of diagnosing the neutrino mass hierachies in the HDE model. However, the difference of is still not significant enough to distinguish the neutrino mass hierarchies, even though the minimal of the normal hierarchy is slightly smaller than that of the inverted hierarchy.

Paper Structure

This paper contains 4 sections, 6 equations, 3 figures, 3 tables.

Table of Contents

  1. Introduction
  2. Methodology
  3. Results
  4. Conclusion

Figures (3)

  • Figure 1: The $68\%$ and $95\%$ CL marginalized contours of $\sum m_\nu$ and $w$ in the $w$CDM model by using the Planck TT,TE,EE + lowP + BAO + JLA + $H_0$ + Lensing data, in the case of considering neutrino mass hierarchies.
  • Figure 2: The $68\%$ and $95\%$ CL marginalized contours of $\sum m_\nu$ and $c$ in the HDE model by using the Planck TT,TE,EE + lowP + BAO + JLA + $H_0$ + Lensing data, in the case of considering neutrino mass hierarchies.
  • Figure 3: The posterior probability distributions of $H_0$ in three dark energy models with three degenerate neutrinos. The red dot-dashed vertical line denotes the central value of the local $H_0$ measurement, and the orange (yellow) shaded area denotes the $1\sigma$ ($2\sigma$) uncertainty. Here $A$, $B$ and $C$ denote Planck TT,TE,EE+lowP+BAO, Planck TT,TE,EE+lowP+BAO+JLA+$H_0$+Lensing, and Planck TT,TE,EE+lowP+BAO+JLA+Lensing, respectively.