Variants of fattening and flavor symmetry restoration

The MILC Collaboration We study the effects of different " fat link " actions for Kogut-Susskind quarks on flavor symmetry breaking. Our method is mostly empirical-we compute the pion spectrum with different valence quark actions on common sets of sample lattices. Different actions are compared, as best we can, at equivalent physical points. We find significant reductions in flavor symmetry breaking relative to the conventional or to the " link plus staple " actions, with a reasonable cost in computer time. We also develop and test a scheme for approximate unitarization of the fat links. While our tests have concentrated on the valence quark action, our results will be useful in designing simulations with dynamical quarks.