LATTICE QCD WITHOUT TUNING, MIXING AND CURRENT RENORMALIZATION

The classically perfect action of QCD requires no tuning to get the pi on massless in the broken phase: the critical bare mass m(q)(c) is zer o. Neither the vector nor the flavour non-singlet axial vector current s need renormalization. Further, there is no mixing between 4-fermion operators in different chiral representations. The order parameter of chiral symmetry requires, however, a subtraction which is given here e xplicitly. These results are based on the fact that the fixed point ac tion satisfies the Ginsparg-Wilson remnant chiral symmetry condition. On chiral symmetry related questions any other local solution of this condition will produce similar results. (C) 1998 Elsevier Science B.V.