The interplay between the <A^2> condensate and instantons
  Using the Local Composite Operator formalism, we analytically study the dimension two gluon condensate in the presence of instantons. We first use the dilute gas approximation and partially solve the infrared problem of instanton physics. In order to find quantitative results, however, we turn to an instanton liquid model, where we find a two-component picture of the condensate: one component comes from instantons, a second component is non-perturbatively generated by quantum fluctuations around the instantons. 
David Vercauteren, Henri Verschelde
hep-th