Vortex Loops In The 3-d XY Model
  We study the properties of vortex loops in the 3-d XY model. We find that the phase transition in this model is driven by the condensation of short loops into percolating loops. Paper comes as a uuencoded compressed tar-file, containing the complete PostScript file. Total file approx. 220 Kb. 
Arjan Hulsebos