Motion of an object through a quantum fluid

We simulate the motion of a massive object through a dilute Bose-Einstein c ondensate by numerical solution of the Gross-Pitaevskii equation coupled to an equation of motion for the object. Under a constant applied force, the object accelerates up to a maximum velocity where a vortex ring is formed w hich slows the object down. If the applied force is less than a critical va lue, the object becomes trapped within the vortex core. We show that the mo tion follows the time-independent solutions, and use these solutions to pre dict the conditions required for vortex detachment.