Approximated seventh order calculation of vacuum wave function of 2+1   dimensional SU(2) lattice gauge theory
  Using the coupled cluster expansion with the random phase approximation, we calculate the long wavelength vacuum wave function and the vacuum energy of 2+1 dimensional Hamiltonian SU(2) lattice gauge theory (LGT) up to the seventh order. The coefficients $\mu_0$, $\mu_2$ of the vacuum wave function show good scaling behavior and convergence in high order calculations. 
Ping Hui, Xi-Yan Fang, Ting-yun Shi