Hadronic Correlators and Condensate Fluctuations in QCD Vacuum
  Phenomenological results of equal time, point to point spatial correlation functions of hadronic currents are used to deduce the structure of the QCD vacuum. It is found that a model with only quark condensate is not adequate to explain the observations. Inclusion of condensate fluctuations (explicit four point structure in the vacuum) leads to excellent overall agreement with the phenomenological curves and parameters in various channels. 
Varun Sheel, Hiranmaya Mishra and Jitendra C. Parikh