Sampling of general correlators in worm-algorithm based simulations

Abstract

Using the complex φ4-model as a prototype for a system which is simulated by a worm algorithm, we show that not only the charged correlator 〈φ*(x)φ(y)〉, but also more general correlators such as 〈|φ(x)||φ(y)|〉 or 〈arg (φ(x))arg (φ(y))〉, as well as condensates like 〈|φ|〉, can be measured at every step of the Monte Carlo evolution of the worm instead of on closed-worm configurations only. The method generalizes straightforwardly to other systems simulated by worms, such as spin or sigma models.