Stochastic method for analytic continuation of quantum Monte Carlo data

A method for analytic continuation of quantum Monte Carlo data is presented. The spectrum A(omega) is parametrized as a sum of delta functions, the weights A(i) of which are sampled according to a distribution p(A) similar to exp(-chi(2)/Theta). It is argued that the calculated entropy S provides a criterion for determining the Theta corresponding to the "best" averaged spectrum. The appearance of spurious structure is signaled by a sharp drop in (S(Theta)), which in test cases is preceded by a local maximum. Results for the dynamic spin structure factor of a 16-site Heisenberg chain obtained at this maximum are in better agreement with exact results than "classic" maximum-entropy results. [S0163-1829(98)02717-9].