Rare Muon Decays, Natural Lepton Models, and Doubly Charged Leptons

Simple, natural model of leptons are presented in which the rare decays μ→eγ and μ→3e occur. The models require doubly charged leptons. The experimental lower limit on the mass of doubly charged leptons determines an upper limit on Γ(μ→3e)Γ(μ→eγ). Parity nonconservation in atoms may be small.