Equivariant Gauge Fixing of SU(2) Lattice Gauge Theory

Abstract

I construct a Lattice Gauge Theory (LGT) with discrete Z_2 structure group and an equivariant BRST symmetry that is physically equivalent to the standard SU(2)-LGT. The measure of this Z_2-LGT is invariant under all the discrete symmetries of the lattice and its partition function does not vanish. The Topological Lattice Theories (TLT) that localize on the moduli spaces are explicitly constructed and their BRST symmetry is exhibited. The ghosts of the Z_2-invariant local LGT are integrated in favor of a nonlocal bosonic measure. In addition to the SU(2) link variables and the coupling g^2, this effective bosonic measure also depends on an auxiliary gauge invariant site variable of canonical dimension two and on a gauge parameter \alpha. The relation between the expectation value of the auxiliary field, the gauge parameter \alpha and the lattice spacing $a$ is obtained to lowest order in the loop expansion. In four dimensions and the critical limit this expectation value is a physical scale proportional to \Lambda_L in the gauge \alpha=g^2 (11-n_f)/24+ O(g^4). Implications for the loop expansion of observables in such a critical gauge are discussed.