Variational method and duality in the 2D square Potts model
arXiv:cond-mat/9705062 · doi:10.1088/0305-4470/30/22/008
Abstract
The ferromagnetic q-state Potts model on a square lattice is analyzed, for q>4, through an elaborate version of the operatorial variational method. In the variational approach proposed in the paper, the duality relations are exactly satisfied, involving at a more fundamental level, a duality relationship between variational parameters. Besides some exact predictions, the approach is very effective in the numerical estimates over the whole range of temperature and can be systematically improved.
20 pages, 5 EPS figures