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arXiv · 2603.15422

When One-Parameter Dark Energy Makes Neutrinos Physical Again

Weiqiang Yang·Eleonora Di Valentino·Eric V. Linder·Sibo Zhang·Supriya Pan
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Abstract

A puzzling implication of current data interpreted in the $\Lambda$CDM cosmology is the preference for a negative sum of neutrino masses. Moving to $w_0w_a$CDM brings an appreciable fraction of the neutrino mass posterior back to positive values, while the constant equation-of-state dark energy case $w$CDM does not. We investigate a variety of one-parameter dark energy equations of state (DE EoS), each variation with particular physical properties, to understand whether a two-parameter DE EoS is required to bring the neutrino mass positive. The conclusion is that certain one-parameter DE EoS can suffice, implying that the data are pointing toward physical characteristics rather than a broad degeneracy. The required characteristics are identified as phantom dark energy at high redshift, crossing $w=-1$ at lower redshift.

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Weiqiang Yang, Eleonora Di Valentino, Eric V. Linder, Sibo Zhang, Supriya Pan. 2026-03-16. When One-Parameter Dark Energy Makes Neutrinos Physical Again. https://arxiv.org/abs/2603.15422

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