Overcoming the fermion sign problem in homogeneous systems

nd that individual exchange probabilities in homogeneous systems are, except for nite size eects, independent of the conguration of other permutations present. For two representative systems, 3 He and the homogeneous electron gas, we show that this allows the entire antisymmetrized density matrix to be generated from a simple model depending on only a few parameters obtainable directly from a standard PIMC simulation. The result is a polynomial scaling algorithm and up to a 10 order of magnitude increase in eciency in measuring fermionic observables for the systems considered. Path integral Monte Carlo (PIMC) methods provide essentially exact results for low temperature properties of N-body Bosonic systems [3]. While the same algorithm can be applied to Fermions, a sign problem arising from the approximately equal weights of the N! oppositely signed permutations, limits the accuracy of the results. In fact, naive application of the PIMC method to fermions results in exponentially decreasing eciency as the temper