On charge conservation and baryon-number violation in the monopole-fermion system

Around the 't Hooft-Polyakov monopole, charged fermion fields satisfy a peculiar boundary condition which mixes different U(1)-charge states at the monopole core. In a perturbative semi-classical treatment, this seems to imply violation of the charge superselection rule. It is explicitly demonstrated how this difficulty is resolved when higher order corrections are taken into account. We also show that the charge mixing boundary condition is essential for the monopole catalysis of baryon decay and that the chiral anomaly is not directly responsible for this effect. All non-trivial local fermion condensates are derived for an arbitrary number of fermion flavours.