Talk presented by Michael Mueller-Preussker

Parallel Session: Theoretical Developments II

Friday July 2nd, 15.10 - 15.30, Room 8

Lorentz gauge fixing, the Gribov problem and the fermion correlator in lattice compact QED with Wilson fermions

Abstract: The Gribov problem for the Lorentz (Landau) gauge is discussed in case of compact QED with Wilson fermions within the quenched approximation. For the Coulomb phase the gauge copies are shown to be mainly caused by double Dirac sheets and zero-momentum modes. The removal of both of them is necessary in order to reach the global extremum of the gauge functional. A corresponding gauge fixing prescription - the 'zero-momentum Lorentz (ZML) gauge' - is proposed. The fermion correlation function is computed for ZML in comparison with other commonly applied gauge fixing procedures. In all latter cases the correlator is shown to be dominated by zero-momentum modes and to deviate significantly from the expected perturbative result. In contrast to that, for ZML the fermion propagator is found to behave properly in accordance with perturbation theory. Only in this case the fermion mass can be reliably extracted and agrees well with the value determined from a Ward identity. We discuss possible implications for gauge fixing in QCD.

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