Vacuum Structure in QCD with Quark and Gluon Condensates
  We consider here the vacuum structure in QCD with both quark and gluon condensates and a variational ansatz for the ground state. The method is nonperturbative using only equal time algebra for the field operators. We then find that a constrained energy minimisation of the Hamiltonian leads to a QCD vacuum with both quark and gluon condensates for $\alpha_s > \alpha_c=0.62$. Pion decay constant and the charge radius of the pion seem to fix the QCD coupling constant $\alpha_s$ as 1.28. The approach opens up possibilities of relating the mysterious vacuum structure with common place hadronic properties. 
A. Mishra, H. Mishra, Varun Sheel, S.P. Misra and P.K. Panda