Time Delay and the Dyon Charge

The scattering of fermions from a magnetic monopole is analyzed in a theory with $\mathrm{CP}$ nonconservation. The dyon charge that arises can be understood as a Friedel sum rule from the theory of alloys, as the data for a Riemann-Hilbert problem in the theory of integral equations, and as a consequence of specifying Wigner's $R$ matrix at the monopole core.