The Schwinger model with perfect staggered fermions

We construct and test a quasi-perfect lattice action for staggered fermions . The construction starts from free fermions, where we suggest a new blocki ng scheme, which leads to excellent locality of the perfect action. An adeq uate truncation preserves a high quality of the free action. An Abelian gau ge field is inserted in d = 2 by effectively tuning the couplings to a few short-ranged lattice paths, based on the behavior of topological zero-modes . We simulate the Schwinger model with this action, applying a new variant of Hybrid Monte Carlo, which damps the computational overhead due to the no n-standard couplings. We obtain a tiny "pion" mass down to very small beta, while the "eta" mass follows very closely the prediction of asymptotic sca ling. The observation that even short-ranged quasi-perfect actions can yiel d strong improvement is most relevant in view of QCD. (C) 1999 Elsevier Sci ence B.V. All rights reserved.