Neutrinoless double beta decay, Leptogenesis, and gauged U(1)_μ-τ models.

We will review the Leptogenesis, a mechanism to create the matter-antimatter asymmetry of the Universe, and its implication for the neutrinoless double beta decay. We also discuss extensions of the Standard Model with gauged U(1)_μ-τ symmetry, which predicts a large rate of the neutrinoless double beta decay.