Worm Algorithm for Continuous-space Path Integral Monte Carlo   Simulations
  We present a new approach to path integral Monte Carlo (PIMC) simulations based on the worm algorithm, originally developed for lattice models and extended here to continuous-space many-body systems. The scheme allows for efficient computation of thermodynamic properties, including winding numbers and off-diagonal correlations, for systems of much greater size than that accessible to conventional PIMC. As an illustrative application of the method, we simulate the superfluid transition of Helium-four in two dimensions. 
M. Boninsegni, N. Prokof'ev and B. Svistunov