Rare tau decays via exchange of on-shell almost degenerate Majorana neutrinos, τ∓ → π∓Nj → π∓μ∓π± and τ∓ → π∓Nj → π∓μ±π∓

We investigate rare decays of tau leptons that occur via exchange of heavy on -shell neutrinos N-j (j =1,2). These neutrinos can be either Dirac or Majorana, and are considered to be almost degenerate in mass. The decays can thus be either lepton number c