An Almost Perfect Lattice Action for infrared QCD
  A block-spin transformation on the dual lattice leads us to an almost perfect lattice action for monopoles and strings in QCD. The perfect operator for a static quark potential is fixed when we compare the above action with the perfect action obtained analytically after infinite-step block-spin transformations in a simple case. The continuum rotational invariance is restored and the physical value of the string tension is reproduced fairly well. Gauge independence of the abelian and the monopole scenario is discussed. 
T.Suzuki