Worm algorithm in quantum Monte Carlo simulations

We present a novel quantum Monte Carlo scheme which allows efficient calculations of the Green function at finite temperature and the study of large disordered systems. The scheme is ergodic, works with non-zero winding numbers and in the grand canonical ensemble. The central idea is using a pair of worldline discontinuities for sampling the extended configuration space of the system which includes both closed and disconnected worldlines. The method is illustrated by simulations of pure and disordered bosonic Hubbard models in 1D. (C) 1998 Published by Elsevier Science B.V.