Testing perturbative results with non-perturbative methods for the   Hierarchical model
  We present non-perturbative methods to calculate accurately the renormalized quantities for Dyson's Hierarchical Model. We apply this method and calculate the critical exponent gamma with 12 and 4 significant digits in the high and low temperature phases, respectively. We report accurate values for universal ratios of amplitudes and preliminary results concerning the comparison with perturbative results. 
Y. Meurice and M. B. Oktay (The University of Iowa)