Based on general arguments on how to construct the effective theory of
hadrons (i.e. chiral perturbation theory--chiPT) from QCD, one may
arrive at a model with charge-parity (CP) violation, suggesting e.g. an
electric dipole moment for the neutron. However, the way in which the CP
phases of QCD appear in chiPT is not unique. In particular, it is
perfectly possible for these not to show up at all. The actual
prediction from QCD, i.e. that there is no CP violation, can be
understood when taking into account that the contour of path integration
subsequently sweeps over complete topological sectors (i.e. the
different ways in which one sphere may be wrapped around another) in
infinite spacetime volume. A complementary argument is that in contrast
to the commonly discussed theta-vacua that are reminescent of Bloch
states, the wave-functionals in the strong interactions are after all
properly normalizable. Their form is pinned uniquely by demanding that
the gauge-fixed Hamiltonian is Hermitian.
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