Monte Carlo simulation combined with a hopping parameter expansion

Abstract

The fermionic contribution to the effective action is a sum over simple closed loops in configuration space. Loops, which are much larger than the characteristic length of the problem are expected to be irrelevant. In the parameter region where the characteristic length is small, an expansion in the size of the loops is suggested. The method was used on a 2 4 lattice in SU(2) with two flavours in order to compare with the results of Weingarten and Petcher, who simulated the complete action. We have reproduced their results. Using this technique the computer time is reduced by orders of magnitude.