Dr Michael Teper

Abstract:

We discuss some aspects of the hadron spectrum with two flavors of Kogut-Susskind dynamical quarks at 6/g2 = 5.6 and amq = 0.01 and 0.025, using both Kogut-Susskind and Wilson valence quarks. Our high statistics simulations allow us to study systematic errors. Among the problematic features of our results are a dip in the pion effective mass which we ascribe to replicating the lattice in the time direction and large finite size effects in the baryon masses. We also compare the full QCD results to a quenched simulation at similar lattice spacing and quark masses to test whether the effects of dynamical fermions can be absorbed into renormalization of the lattice parameters. © 1991.

Abstract:

I focus on three topics in my review of pure gauge theories. Firstly, how close are we to solving the continuum theory. Secondly, cooling and confinement. Thirdly, the status of lattice topology. © 1991.

Abstract:

We present results from a study of hadron thermodynamics with Wilson quarks. The crossover curve between the high and low temperature phases is determined as a function of the gauge coupling and hopping parameter on 83 × 4 lattices. Meson masses are calculated along the crossover curve, and screening lengths are determined in the vicinity of it on 83 × 16 and 82 × 16 × 4 lattices, respectively. © 1991.

Abstract:

We investigate some basic aspects of topological fluctuations in lattice QCD, in the version with two colours and four light flavours; and we do so in both the confining, chiral symmetry broken phase and in the non-confining, chirally symmetric phase. This latter phase is found to ccut not only high temperatures, just as in the pure gauge system, but also in small spatial volumes, which is unlike the pure gauge case. We derive the way the topological susceptibility should vary with quark mass at small quark masses. We find that the calculated topological susceptibility decerases to zero with the quark mass, with the theretically expected powers except - in the symmetric phase - at the very smallest values of the quark mass. We demonstrate that this anomalous behaviour can be understood as arising from the fact that the lattice topological "zero modes" are in fact sufficiently far from being zero. We also show, in the chirally symmetric phase, that, just as expected, the average distance between instantons and anti-instantons decreases with decreasing quark mass. We finish with a new and more precise estimate of the location of the finite-temperature transition in SU(2) with four light flavours. © 1991.

Abstract:

We obtain estimates of the lightest glueball masses, the string tension, and the topological susceptibility in an exploratory study of QCD with two light flavors of quarks. Our calculations are performed at =5.6 with staggered quark masses mq=0.010 and 0.025 and on lattices ranging from 124 to 164. Our estimates suggest that, just as in the pure gauge theory, the 0++ is the lightest glueball with the 2++ about 50% heavier. Our mq=0.01 results predict a 0++ glueball mass of about 1.6 times the mass and the square root of the string tension of about 0.48 times the mass, which is surprisingly close to the usual phenomenologically motivated estimates of around 0.55. Our value of the topological susceptibility at mq=0.01 is consistent with the prediction, to O(mq) of the standard anomalous Ward identity. However, the variation of this susceptibility between mq=0.01 and mq=0.025 is weaker than the linear dependence one expects at small mq in the broken-chiral-symmetry phase of QCD. © 1991 The American Physical Society.