On the strong-CP problem in models with several Higgs multiplets and supersymmetry

We point out that the strong- CP problem becomes even more pressing in the context of weak models where CP violation originates in the Higgs sector. θ renormalization is numerically too large at the one-loop level and even divergent at the two-loop level. When supersymmetry (SUSY) is introduced, many more possible sources for CP violation open up. θ renormalization could stay finite in perturbation theory, however, we find that the one-loop result turns out to be too large by orders of magnitude unless SUSY fields like gauginos and higgsinos are highly degenerate in mass or SUSY breaking proceeds in a very special way, or a Peccei-Quinn symmetry holds leading to superlight axions.