Negative neutrino masses as a mirage of dark energy

TL;DR

This paper introduces an effective neutrino mass parameter allowing negative values to test cosmological constraints against laboratory data, revealing tensions and the influence of dark energy models on neutrino mass estimates.

Contribution

It proposes a novel effective neutrino mass parameter extending to negative values, enabling direct comparison of cosmological and laboratory constraints without priors.

Findings

Detected a 2.8-3.3σ tension with oscillation experiment constraints.

Dark energy models can reconcile cosmological neutrino mass estimates with laboratory data.

Negative neutrino masses can mimic dark energy effects in cosmological data.

Abstract

The latest cosmological constraints on the sum of the neutrino masses depend on prior physical assumptions about the mass spectrum. To test the accordance of cosmological and laboratory constraints in the absence of such priors, we introduce an effective neutrino mass parameter that extends consistently to negative values. For the $\Lambda$CDM model, we analyze data from Planck, ACT, and DESI and find a $2.8-3.3\sigma$ tension with the constraints from oscillation experiments. Motivated by recent hints of evolving dark energy, we analyze the $w_0w_a$ and mirage dark energy models, showing that they favour larger masses consistent with laboratory data, respectively $\sum m_{\nu,\mathrm{eff}} = 0.06_{-0.10}^{+0.15}\,\mathrm{eV}$ and $\sum m_{\nu,\mathrm{eff}} = 0.04_{-0.11}^{+0.15}\,\mathrm{eV}$ (both at 68%).