Quenched Chiral Artifacts for Wilson-Dirac Fermions
  We examine artifacts associated with the chiral symmetry breaking induced through the use of Wilson-Dirac fermions in lattice Monte Carlo computations. For light quark masses, the conventional quenched theory can not be defined using direct Monte Carlo methods due to the existence of nonintegrable poles in physical quantities. These poles are associated with the real eigenvalue spectrum of the Wilson-Dirac operator. We show how this singularity structure can be observed in the analysis of both QED in two dimensions and QCD in four dimensions. 
W. Bardeen (Fermilab), A. Duncan (Univ. of Pittsburgh), E. Eichten   (Fermilab) and H. Thacker (Univ. of Virginia)