Nucleation of vortices in superfluid helium-4

Summary Nucleation of vortices and strings is studied in superfluid helium in the context of phase transitions in this system. It is shown that the formation of these structures depends on the homotopy groups of the manifold of degenerate condensed states. The subsequent evolution of these structures is investigated and then impact on the superfluid nature of this system is analysed. The cross-section for the scattering of quasi-particles is estimated. This is exploited to find the effect of scatterings on the dynamics of shrinking vortex. During the editorial procedure we came to know that this author deceased.