TOWARDS HIGHLY IMPROVED QUARK ACTIONS

We describe two ideas useful in the construction of highly improved qu ark actions for simulations on coarse lattices: (i) Field transformati ons solve the doubler problem without destroying tree-level improvemen t for on- or off-shell quantities. The simplest example is the Sheikho leslami-Wohlert (clover) action. Going to the next order of improvemen t yields the class of D234 actions. (ii) Anisotropic lattices with a(t ) < a(s) are useful because they push up the energy of unphysical bran ches of the dispersion relation (which are generic to highly improved actions), allow accurate mass determinations for particles with bad si gnal/noise properties (glueballs, P-state mesons), and enable one to s imulate heavy quarks within a relativistic framework. We present first simulation results for the quenched light hadron and charmonium spect ra obtained with a D234 action on anisotropic lattices.