The nature of massive neutrinos and multiple mechanisms in neutrinoless double beta decay

Determining the nature -Dirac or Majorana- of massive neutrinos is one of the most pressing and challenging problems in the field of neutrino physics. We discuss how one can possibly extract information on the couplings, if any, which might be involved in neutrinoless double beta-decay using a multi-isotope approach. We investigate as well the potential of combining data on the half-lives of nuclides which largely different Nuclear Matrix Elements such as $^{136}$Xe and of one or more of the four nuclei $^{76}$Ge, $^{82}$Se, $^{100}$Mo and $^{130}$Te, for discriminating between different pairs of non-interfering or interfering mechanisms of neutrinoless double beta-decay. The case studies do not extend to the evaluation of the theoretical uncertainties of the results, due to the nuclear matrix elements calculations and other causes.