Baryogenesis through axion domain wall
  Generic axion models give rise to axion domain walls in the early Universe and they have to disappear not to overclose the universe, thus limiting the nature of discrete symmetry allowed in these type of models. Through QCD sphalerons, net chiral charge can be created by these collapsing walls which in turn can result the observed baryon assymmetry. 
S.N. Nayak and U.A. Yajnik