Casimir-like drag force in a slow-moving superfluid

It is widely accepted that a superfluid flow exhibits a critical velocity~below which there is no dissipation.~However, the often-neglected zero-temperature quantum fluctuations have implications for the existence of~this critical velocity. The drag force on an object created by the scattering of these quantum fluctuations in a three-dimensional, weakly ~interacting Bose-Einstein condensate is discussed.~ A non-zero force at low velocities is found to exist for two specific experimentally realizable examples, which suggests that the effective critical velocity in these systems is zero.