  We use a two-channel model to investigate an interacting Bose gas across a
narrow Feshbach resonance within a field path integral approach. The ground
state properties show strong deviation from that of a broad Feshbach resonance
or a single channel interaction. The deviation can be interpreted by the strong
energy dependence of two-body scattering length near a narrow Feshbach
resonance. As the density increases, the chemical potential and energy per
particle are found to saturate while the inverse compressibility and phonon
velocity undergo a significant reduction. We also take Gaussian fluctuations
into account and calculate the ground state energy correction as well as the
quantum depletion.
