F. Direnzo et al., 4-LOOP RESULT IN SU(3) LATTICE GAUGE-THEORY BY A STOCHASTIC METHOD - LATTICE CORRECTION TO THE CONDENSATE, Nuclear physics. B, 426(3), 1994, pp. 675-685
We describe a stochastic technique which allows one to compute numeric
ally the coefficients of the weak-coupling perturbative expansion of a
ny observable in Lattice Gauge Theory. The idea is to insert the expon
ential representation of the link variables U(mu)(x) --> exp{A(mu)(x)/
square-root beta} into the Langevin algorithm and the observables and
to perform the expansion in beta-1/2. The Langevin algorithm is conver
ted into an infinite hierarchy of maps which can be exactly truncated
at any order. We give the result for the simple plaquette of SU(3) up
to fourth loop order (beta-4) which extends by one loop the previously
known series.