  We study a scenario in which the baryon asymmetry of the universe arises from
a cosmological phase transition where lepton-number is spontaneously broken. If
the phase transition is first order, a lepton-number asymmetry can arise at the
bubble wall, through dynamics similar to electroweak baryogenesis, but
involving right-handed neutrinos. In addition to the usual neutrinoless double
beta decay in nuclear experiments, the model may be probed through a variety of
"baryogenesis by-products," which include a stochastic background of
gravitational waves created by the colliding bubbles. Depending on the model,
other aspects may include a network of topological defects that produce their
own gravitational waves, additional contribution to dark radiation, and a light
pseudo-Goldstone boson (majoron) as dark matter candidate.
