Dissipative dynamics of vortex lines in superfluid $^{4}$He
  We propose a Hamiltonian model that describes the interaction between a vortex line in superfluid $^{4}$He and the gas of elementary excitations. An equation of irreversible motion for the density operator of the vortex, regarded as a macroscopic quantum particle with a finite mass, is derived in the frame of Generalized Master Equations. This enables us to cast the effect of the coupling as a drag force with one reactive and one dissipative component, in agreement with the assumption of the phenomenological theories of vortex mutual friction in the two fluid model. 
H. M. Cataldo, M. A. Desp\'osito, E. S. Hern\'andez and D. M. Jezek