Fixed point action and topological charge for SU(2) gauge theory

We present a theoretically consistent definition of the topological charge operator based on renormalization group arguments. Results of the measurement of the topological susceptibility at zero and finite temperature for SU(2) gauge theory are presented.Comment: 3 pages, LaTeX file. Talk presented at LATTICE96(improvement

The role of heavy fermions

Heavy dynamical fermions with masses around the cut-off do not change the low energy physics apart from a finite renormalization of the gauge coupling. In this paper we study how light the heavy fermions have to be to cause more than this trivial renormalization.Comment: uuencoded 3 page postscript contribution to Lattice 93, COLO-HEP-33

Static screening lengths in the gluon plasma

Journal ArticleWe report results of an extensive numerical simulation in lattice gauge theory to study various static screening lengths in a finite-temperature pure gluon plasma. Measurements are made for fixed triplet charges (Wilson lines) and a variety of local operators near and above the phase transition for lattices with Nt = 4, 6, and 8. We find evidence for a sharp rise in the Wilson-line screening length near the phase transition, but not in screening lengths associated with other operators. We also find evidence for a possible scaling of the inverse screening lengths with temperature above the phase transition. Our results support the proposition that the gluon plasma has a complex structure, and suggest that its long-range nonhydrodynamic excitations just above the phase transition are associated with a color-singlet plasmonlike mode

Thermodynamic properties of the gluon plasma

Journal ArticleWe calculate the energy density, pressure, and speed of sound in the deconfined phase of lattice SU(3) gauge theory at finite temperature for lattices of temporal size N,=4, 6, and 8. We compare our results with perturbative QCD at high temperature and with a simple phenomenological model. We also parametrize our results using the "bag" equation of state

Comment on ``Evidence Against Instanton Dominance of Topological Charge Fluctuations in QCD''

We comment on the recent paper (hep-lat/0102003) by Horvath, Isgur, McCune, and Thacker, which concludes that the local chiral structure of fermionic eigenmodes is not consistent with instanton dominance. Our calculations, done with an overlap action, suggest the opposite conclusion.Comment: 5 pages, Revtex, 4 postscript figures. COLO-HEP-45

Wave functions and their use in spectroscopy and phenomenology

We describe the calculation of Coulomb gauge wave functions for light quark systems, and their use as interpolating fields for excited state spectroscopy.Comment: 4 pages latex with lat92 macro plus 4 postscript figs, COLO-HEP-29

Phase structure of SU(3) gauge theory with two flavors of symmetric-representation fermions

We have performed numerical simulations of SU(3) gauge theory coupled to Nf=2 flavors of symmetric representation fermions. The fermions are discretized with the tadpole-improved clover action. Our simulations are done on lattices of length L=6, 8, and 12. In all simulation volumes we observe a crossover from a strongly coupled confined phase to a weak coupling deconfined phase. Degeneracies in screening masses, plus the behavior of the pseudoscalar decay constant, indicate that the deconfined phase is also a phase in which chiral symmetry is restored. The movement of the confinement transition as the volume is changed is consistent with avoidance of the basin of attraction of an infrared fixed point of the massless theory.Comment: 12 pages, 11 figure