2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/48802If a family symmetry exists so that all three neutrinos have equal Majorana masses (via the seesaw mechanism), then the breaking of this symmetry from charged-lepton masses (via two-loop double $W$ exchange) implies $Δm$ less than about $10^{-9}m_0$. With the common mass $m_0 \sim$ eV for hot dark matter, $Δm^2 \sim 10^{-10}$ eV$^2$ is natural for vacuum solar neutrino oscillations.8 pages including 1 figure, talk at WIN99High Energy Physics - Phenomenologytext