MEASURING THE DECORRELATION TIMES OF FOURIER MODES IN SIMULATIONS

We describe a method to study the rate at which modes decorrelate in n umerical simulations. We study the XY model updated with the Metropoli s and Wolff dynamics respectively and compute the rate at which each e igenvector of the dynamics decorrelates. Our method allows us to ident ify the decorrelation time for each mode separately. We find that the autocorrelation function of the various modes is markedly different fo r the ''local'' Metropolis compared to the ''non-local'' Wolff dynamic s. Equipped with this new insight, it may be possible to devise highly efficient algorithms.