We elaborate on an earlier discussion of $\mathrm{CP}$ conservation of strong interactions which includes the effect of pseudoparticles. We discuss what happens in theories of the quantum-chromodynamics type when we include weak and electromagnetic interactions. We find that strong $\mathrm{CP}$ conservation remains a natural symmetry if the full Lagrangian possesses a chiral U(1) invariance. We illustrate our results by considering in detail a recent model of (weak) $\mathrm{CP}$ nonconservation.

• Received 31 May 1977

DOI:https://doi.org/10.1103/PhysRevD.16.1791