SIMULATIONS OF DISCRETE QUANTUM-SYSTEMS IN CONTINUOUS EUCLIDEAN TIME

We propose a new method to study path integrals for discrete quantum s ystems in which we work directly in the Euclidean time continuum. The method is of general interest. Here it is applied to the Heisenberg qu antum antiferromagnet using a continuous-time version of a loop cluste r algorithm. This algorithm is exploited to confirm the predictions of chiral perturbation theory in the extreme low temperature regime, dow n to T = 0.01J. A fit of the low-energy parameters of chiral perturbat ion theory gives excellent agreement with previous results and with ex periments.