Upper bound on the scale of Majorana-neutrino mass generation.
We derive a model-independent upper bound on the scale of Majorana-neutrino mass generation. The upper bound is 4pi (nu2)/square root3 m(nu), where nu approximately 246 GeV is the weak scale and m(nu) is the Majorana-neutrino mass. For neutrino masses implied by neutrino oscillation experiments, all but one of these bounds are less than the Planck scale, and they are all within a few orders of magnitude of the grand-unification scale.