  We study the influence of a magnetic impurity or ultrasmall quantum dot on
the charge persistent current of a mesoscopic ring. The system consists of
electrons in a one-dimensional ring threaded by spin-dependent
Aharonov-Bohm/Casher fluxes, coupled via an antiferromagnetic exchange
interaction to a localized electron. By passing to a basis of electron states
with definite parities, the problem is mapped onto a Kondo model for the
even-parity channel plus free electrons in the odd-parity channel. States of
opposite parities decouple for values of the flux corresponding to periodic or
antiperiodic boundary conditions. For these special cases, the model is solved
exactly by a Bethe ansatz, allowing for an exact calculation of the charge
persistent current. In particular we show that the charge stiffness in the
special case of spin-independent fluxes is insensitive to the presence of the
magnetic impurity/quantum dot.
