  The spectrum of a charged particle coupled to Aharonov-Bohm/anyon gauge
fields displays a nonanalytic behavior in the coupling constant. Within
perturbation theory, this gives rise to certain singularities which can be
handled by adding a repulsive contact term to the Hamiltonian. We discuss the
case of smeared flux tubes with an arbitrary profile and show that the contact
term can be interpreted as the coupling of a magnetic moment spinlike degree of
freedom to the magnetic field inside the flux tube. We also clarify the ansatz
for the redefinition of the wave function.
