The sign problem in real-time path integral simulations: using the cumulant action to implement multilevel blocking.
A practical method to tackle the sign problem in real-time path integral simulations is proposed based on the multilevel blocking idea. The formulation is made possible by using a cumulant expansion of the action, which in addition to addressing the sign problem, provides an unbiased estimator for the action from a statistically noisy sample of real-time paths. The cumulant formulation also allows the analytical gradients of the action to be computed with little extra computational effort, and it can easily be implemented in a massively parallel environment.
Mak
C H
CH
Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482, USA. mak@tyrosine.usc.edu