PUB - Publikationen an der Universität Bielefeld

Temporal quark correlation functions are analyzed in quenched lattice QCD fortwo values of temperature above the critical temperature (Tc) fordeconfinement, T=1.5Tc and 3Tc. A two-pole ansatz for the quark spectralfunction is used to determine the bare quark mass and the momentum dependenceof excitation spectra on large lattices of size up to 128^3x16. The dependenceof the quark correlator on these parameters as well as the finite volumedependence of the excitation energies are analyzed in detail in order toexamine the reliability of our analysis. Our results suggest the existence ofquasi-particle peaks in the quark spectrum. We furthermore find evidence thatthe dispersion relation of the plasmino mode has a minimum at non-zero momentumeven in the non-perturbative region near Tc. We also elaborate on theenhancement of the quark correlator near the chiral limit which is observed atT=1.5Tc on about half of the gauge configurations. We attribute this to thepresence of near zero-modes of the fermion matrix that are associated withnon-trivial topology of the gauge configurations.