Baryogenesis and CP violating domain walls in QCD

The analysis of the θ dependence in QCD within an effective Lagrangian approach shows that the vacuum energy Evac(θ) is generically a multi-valued function of θ. This implies the existence of metastable vacua and unstable CP violating domain walls interpolating between them. Such a vacuum structure may lead to a new baryogenesis mechanism which takes place at the QCD scale in the early universe. We emphasise that the suggested ideas for baryogenesis can be, in principle, experimentally tested at RHIC.