Methods to determine the Hausdorff dimension of vortex loops in the   three-dimensional XY model
  The geometric properties of critical fluctuations in the 3D XY model are analyzed. The 3D XY model is a lattice model describing superfluids. We present a direct evaluation of the Hausdorff dimension D_H of the vortex loops which are the critical fluctuations of the 3D XY model. We also present analytical arguments for why \vartheta in the scaling relation \eta_{\phi} + D_H = 2 + \vartheta between D_H and the anomalous scaling dimension of the corresponding field theory, must be zero. 
M. Camarda, F. Siringo, R. Pucci, A. Sudbo, J. Hove