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Title: Is the cosmological neutrino mass limit consistent with oscillation data?
Plain: 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: 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.
Settled by: An independent measurement of the reionization optical depth $\tau$ and CMB lensing at higher precision, combined with final DESI BAO.
Kind: well-posed
Answer type: yes-no
References: (empty)
Literature status: contested
Status 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.
Posed since: 2024