Negative neutrino masses as a mirage of dark energy

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 ΛCDM model, we analyze data from Planck, the Atacama Cosmology Telescope, and the Dark Energy Spectroscopic Instrument and find a 2.8–3.3σ tension with the constraints from oscillation experiments. Motivated by recent hints of evolving dark energy, we analyze the w0wa and mirage dark energy models, finding that they favor larger masses consistent with laboratory data, respectively, Pmνeff ¼ 0.06þ0.15 −0.10 eV and Pmνeff ¼ 0.04þ0.15 −0.11 eV (both at 68%).