Observables of neutrinoless double -decay (open blue band) and of direct neutrino mass determination by single -decay (red) versus the cosmologically relevant sum of neutrino mass eigenvalues for the case of normal hierarchy (a) and of inverted hierarchy (b). The width of the bands/areas is caused by the experimental uncertainties () of the neutrino mixing angles [15] and in the case of also by the completely unknown Majorana- and CP-phases. Uncertainties of the nuclear matrix elements, which enter the determination of from the measured values of half-lives or of half-live limits of neutrinoless double -decay, are not considered.
