Leptogenesis, Dark Matter and Gravitational Waves from Discrete Symmetry Breaking

We analyse a model that connects the neutrino sector and the dark sector of the universe via a mediator $\Phi$, stabilised by a discrete $Z_4$ symmetry that breaks to a remnant $Z_2$ upon $\Phi$ acquiring a non-zero vacuum expectation value ($v_\phi$). The model accounts for the observed baryon asymmetry of the universe via additional contributions to the canonical Type-I leptogenesis. The $Z_4$ symmetry breaking scale ($v_\phi$) in the model not only establishes a connection between the neutrino sector and the dark sector, but could also lead to gravitational wave signals that are within the reach of current and future experimental sensitivities.