COSMO In the literature: contested

Is the cosmological neutrino mass limit consistent with oscillation data?

In plain words

Neutrino oscillation experiments prove that the three neutrino masses add up to at least about 0.06 eV. Assuming the standard model of cosmology, cosmology now allows at most about 0.064 eV, and its best fit prefers even less, which is either a fluke, a sign of new physics, or a hidden error.

Precise statement

In LCDM, DESI DR2 BAO plus CMB gives $\mathrm{sum}\, m_\nu < 0.064\,\mathrm{eV}$ (95 percent; 0.053 eV with the Feldman-Cousins construction), while oscillations require $\mathrm{sum}\, m_\nu \ge 0.059\,\mathrm{eV}$ (normal ordering) or $\ge 0.10\,\mathrm{eV}$ (inverted ordering), and the posterior extended to an effective negative mass peaks below zero. Determine whether a positive $\mathrm{sum}\, m_\nu \ge 0.059\,\mathrm{eV}$ is consistent with the data, or whether the deficit requires new physics (evolving dark energy, modified lensing amplitude, neutrino decay or non-standard interactions) or unrecognized systematics.

What would settle it

An independent measurement of the reionization optical depth $\tau$ and CMB lensing at higher precision, combined with final DESI BAO.

Status in the literature

Unverified note

In a w0-wa cosmology DESI DR2 BAO plus CMB relaxes the bound to sum $m_{\nu}<0.163\,\mathrm{eV}$ (95 percent, 2025), so the conflict depends on the dark energy model.