Model-independent determination of the gluon condensate in   four-dimensional SU(3) gauge theory
  We determine the non-perturbative gluon condensate of four-dimensional SU(3) gauge theory in a model independent way. This is achieved by carefully subtracting high order perturbation theory results from non-perturbative lattice QCD determinations of the average plaquette. No indications of dimension two condensates are found. The value of the gluon condensate turns out to be of a similar size as the intrinsic ambiguity inherent to its definition. 
Gunnar S. Bali, Clemens Bauer and Antonio Pineda
hep-ph hep-lat hep-th