CP Violation from Surface Terms in the Electroweak Theory without   Fermions
  We consider the effect of adding a CP-odd, theta FFdual-term to the electroweak Lagrangian without fermions. This term affects neither the classical nor perturbatively quantum physics, but can be observed through non-perturbative quantum processes. We give an example of such a process by modifying the theory so that it supports Higgs-winding solitons and showing that the rates of decay of these solitons to specific final states are CP violating. We also discuss how the CP symmetry is restored when fermions are included. 
Arthur Lue (Columbia U.), Mark Trodden (Case Western Reserve U.)