Does a Dyon Leak?

Abstract

In the presence of a $\mathrm{CP}$ nonconservation measured by an angle $\theta$, the ground state of a point magnetic monopole is shown to have an electric charge of value $-\frac{e\theta }{2\pi }$ which changes discontinuously to zero for massless fermions. A new version of Levinson's theorm is also given. The latter effect as well as the $S$-wave helicity filp of a dyon can be interpreted as a leak at the origin.