Kohn's theorem in a superfluid Fermi gas with a Feshbach resonance

The dipole mode in a superfluid gas of Fermi atoms trapped in a harmonic potential was analyzed. The frequency of this collective mode was not affected by an interaction between the atoms and was always equal to the trap frequency, according to Kohn's theorem. The effect of a Feshbach resonance and a condensate of the associated molecular bound states was also included. The dipole frequency was shown to depend on the strength of effective interaction associated with the Feshbach resonance, when the molecular bosons feel a different trap frequency from the Fermi atoms.