Correlation Lengths in the Vortex Line Liquid of a High Tc   Superconductor
  We use the three dimensional uniformly frustrated XY model, as a model for a high temperature superconductor in an applied magnetic field, to explicitly measure the longitudinal correlation length xi_z in the vortex line liquid phase. We determine the scaling of xi_z with magnetic field and system anisotropy close to the vortex lattice melting transition. We apply our results to determine the extent of longitudinal correlations in YBCO just above melting. 
Peter Olsson and S. Teitel