  By inverting the seesaw formula we determine the heavy neutrino mass matrix.
The impact on the baryogenesis via leptogenesis and the radiative lepton decays
in supersymmetric models is described. Links to neutrinoless double beta decay
are also briefly discussed. The analysis leads to two distinct matrix models.
One has small mixings while the other has one maximal mixing. Both cannot give
a sufficient amount of baryon asymmetry. Then we also comment on a different
form of the Dirac neutrino mass matrix, which does provide sufficient baryon
asymmetry. In a supersymmetric scenario the branching ratios of radiative
lepton decays are enhanced for this model.
