Superfluid Flow and Local Gauge Invariance

Abstract

A Boss system has two broken symmetries, namely the gauge symmetry and the Galilei translation symmetry. We discuss the microscopic background of the ansatz that the superfluid flow is the manifestation of the local gauge invariance. To do this we show that the depletion velocity fields are the Goldstone fields due to the breakdown of the Galilei translation symmetry. A connection between a Bose-Einstein condensation and superfluid flow is also discussed.