Do dark energy and matter interact? New limits on neutrino mass say maybe—and it's a problem.

Using new DESI observations, researchers tested four models where dark energy and dark matter interact. Depending on how the interaction works, the upper limit on total neutrino mass ranges from 0.051 to 0.129 eV—a spread that matters because neutrino experiments set a lower bound around 0.06 eV. Some models now fit the data better than standard ΛCDM, but also create a direct conflict with known neutrino physics.