  Phase-sensitive transport through a quantum dot coupled to an Aharonov-Bohm
ring is analyzed. In this geometry the spectral density of states is directly
related to the conductance. It is shown that the Kondo resonance depends on the
phase and on the total number of electrons (modulo 4) in the mesoscopic ring.
The effect of the discrete level spacing in the ring and of the coupling to the
electrical leads is discussed.
