  We derive the extension of the Hubbard model to include Rashba spin-orbit
coupling that correctly describes Aharonov-Bohm and Aharonov-Casher phases in a
ring under applied magnetic and electric fields. When the ring is connected to
conducting leads, we develop a formalism that is able to describe both, Kondo
and interference effects. We find that in the Kondo regime, the spin-orbit
coupling reduces strongly the conductance from the unitary limit. This effect
in combination with the magnetic flux, can be used to produce spin polarized
carriers.
