A nonperturbative microscopic theory of Hamiltonian lattice gauge   systems
  A review is given of our recent application of a systematic microscopic formulation of quantum many-body theory, namely the coupled-cluster method (CCM), to Hamiltonian $U(1)$ lattice gauge models in the pure gauge sector. It is emphasized that our CCM results represent a natural extension or resummation of the results from the strong-coupling perturbation theory. 
R.F. Bishop, N.J. Davidson, and Y. Xian