Properties of a Dilute Bose Gas near Feshbach Resonance

In this paper, properties of a homogeneous Bose gas with Feshbach resonance are studied in the dilute region at zero temperature. In the stationary state, there are condensations of atoms and molecules. The ratio of the molecule density to the atom density is proportional to na. There are two types of excitations, molecular excitations and atomic excitations. Atomic excitations are gapless, consistent with the traditional theory of a dilute Bose gas. The molecular excitation energy is finite in the long-wavelength limit as observed in recent experiments. In addition, the decay process of the condensate is studied. The prefactor of the three-body recombination rate is much bigger than that of a Bose gas without Feshbach resonance.