Recent neutrino oscillation experiments have measured leptonic mixing angles with considerable precision. Many theoretical attempts to understand the peculiar mixing structure, observed in these measurements, are based on non-Abelian flavour symmetries. This talk concentrates exclusively on models based on the non-Abelian symmetry A_4. A_4 is particularly well suited to describe three family mixing, and allows to explain the near tri-bimaximal mixing observed. Special emphasis is put here on the discussion of the neutrinoless double beta decay observable . Different models based on A4 with very similar predictions for neutrino angles can yield vastly different expectations for . Neutrinoless double beta decay can thus serve, in principle, as a discriminator between different neutrino mass models.
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AHEP Group, Instituto de Fisica Corpuscular –C.S.I.C./Universitat de Valencia, Edificio de Institutos de Paterna, Apartado 22085, E-46071 Valencia, Spain;