  We investigate Aharonov-Bohm oscillations of the current through a strongly
correlated quantum dot embedded in an arbitrary scattering geometry.
Resonant-tunneling processes lead to a flux-dependent renormalization of the
dot level. As a consequence we obtain a fine structure of the current
oscillations which is controlled by quantum fluctuations. Strong Coulomb
repulsion leads to a continuous bias voltage dependent phase shift and, in the
nonlinear response regime, destroys the symmetry of the differential
conductance under a sign change of the external flux.
