Semiclassical Approximation for Non-Abelian Field Strength Correlators in the Instanton Dilute Gas Model

摘要

Field strength correlators are semi-classically evaluated in the dilute gasmodel of non-Abelian sources (instantons) and compared with lattice data forQCD at zero temperature. We show that one of the Euclidean invariant, tensorialstructures vanishes for configurations being purely selfdual or anti-selfdual.We compute the invariant functions contributing to the correlators within thetwo lowest orders in an instanton density expansion. Fitting instanton size anddensity for quenched and full QCD, we obtain a reasonable description.