Constraints on non-flat cosmologies with massive neutrinos after Planck 2015

TL;DR

This study uses Planck 2015 data combined with other cosmological observations to constrain neutrino masses and spatial curvature in flat and non-flat dark energy models, revealing that curvature broadens parameter bounds.

Contribution

It provides new constraints on neutrino masses and spatial curvature in flat and non-flat cosmologies with dark energy models using comprehensive observational data.

Findings

Neutrino mass bounds are tighter in flat models.

Spatial curvature significantly broadens neutrino mass constraints.

Differences in neutrino hierarchy effects are more pronounced in non-flat models.

Abstract

We investigate two dark energy cosmological models (i.e., the $\Lambda$CDM and $\phi$CDM models) with massive neutrinos assuming two different neutrino mass hierarchies in both the spatially flat and non-flat scenarios, where in the $\phi$CDM model the scalar field possesses an inverse power-law potential, $V(\phi)\propto {\phi}^{-\alpha}$ ($\alpha>0$). Cosmic microwave background data from Planck 2015, baryon acoustic oscillations data from 6dFGS, SDSS-MGS, BOSS-LOWZ and BOSS CMASS-DR11, the JLA compilation of Type Ia supernova apparent magnitude observations, and the Hubble Space Telescope $H_0$ prior, are jointly employed to constrain the model parameters. We first determine constraints assuming three species of degenerate massive neutrinos. In the spatially flat (non-flat) $\Lambda$CDM model, the sum of neutrino masses is bounded as $\Sigma m_{\nu} < 0.165 (0.299)$ eV at 95% confidence level (CL). Correspondingly, in the flat (non-flat) $\phi$CDM model, we find $\Sigma m_{\nu} < 0.164 (0.301)$ eV at 95% CL. The inclusion of spatial curvature as a free parameter results in a significant broadening of confidence regions for $\Sigma m_{\nu}$ and other parameters. In the scenario where the total neutrino mass is dominated by the heaviest neutrino mass eigenstate, we can obtain the similar conclusions as those obtained in the degenerate neutrino mass scenario. In addition, the results show that the bounds on $\Sigma m_{\nu}$ based on two different neutrino mass hierarchies have insignificant differences in the spatially flat case for both the $\Lambda$CDM and $\phi$CDM models, however, the corresponding differences are larger in the non-flat case.