Dynamics of a superfluid vortex and the Magnus force

We study the dynamics of a vortex in superfluid He4. This is carried out by deriving the effective Lagrangian for the center of the vortex by starting with the time-dependent Ginzburg-Landau formalism. From the resultant equation of motion for a vortex, we arrive at a novel aspect for the Magnus force which has long been known in fluid dynamics. This force has a geometric origin and is expected to occur in other form of condensates such as vortex excitations for quantum Hall fluids or ferromagnets. We also consider the force of non geometric origin, the pinning force coming from the impurity.