  The roton in a Bose-Einstein condensate is computed, both near and far from a
Feshbach resonance. A low-density approximation is made, allowing for an
analytic result. A Monte Carlo calculation shows that the roton is larger than
predicted by the low-density approximation, for the upper range of densities
considered here. The low-density approximation is applied to superfluid 4He,
roughly reproducing the results of previous Monte Carlo calculations.
