Instantons and chiral symmetry on the lattice

摘要: I address the question of how much QCD in chiral limit is reproduced by instantons. After reconstructing instanton content smoothed Monte Carlo lattice configurations, compare hadron spectroscopy on this ensemble to original ``physical'' configurations using a chirally optimized clover fermion action. By studying zero mode zone simple instances find that action gives satisfactory description it. Through Banks-Casher formula, instantons themselves are shown break symmetry but correlators backgrounds strongly influenced free quark propagation. This results unnaturally light hadrons and small splitting between vector pseudoscalar meson channels. Superimposing perturbative momentum gauge field fluctuations (torons) found be enough eliminate quarks restore physical correlators. argue torons present only finite volumes probably needed compensate large size effects due lack confinement ensemble.