Improving the Chiral Properties of Lattice Fermions
  The chiral properties of lattice fermions can be improved by altering either their fermion-gauge coupling or the pure gauge part of the action (or both).   Using both perturbation theory and nonperturbative simulation, we compare a simple alteration of the gauge action (which encompasses the Wilson, Symanzik, Iwasaki, and DBW2 actions), and HYP-blocked links in the fermion action. Perturbative tests include calculations of the potential, flavor-changing quark scattering amplitudes, and matching factors for currents. Non-perturbative tests include the potential, measurements of flavor symmetry breaking for staggered fermions, the behavior of topological objects, and properties of overlap actions. Our results display the bad properties of these actions as well as their good ones. 
Thomas DeGrand, Anna Hasenfratz, and Tamas G. Kovacs