Universality, Scaling and Topology with a Modified Lattice Action

We examined the effect of a complete suppression of a lattice artifact, the negative plaquettes, on physical quantities, such as the critical temperature, the string tension, the topological charge, glueball masses, and their ratios.Comment: 3 pages, self unpacking uuencoded PostScript file, contribution to conference LATTICE '9

Improved Upsilon Spectrum with Dynamical Wilson Fermions

We present results for the b \bar b spectrum obtained using an O(M_bv^6)-correct non-relativistic lattice QCD action, where M_b denotes the bare b-quark mass and v^2 is the mean squared quark velocity. Propagators are evaluated on SESAM's three sets of dynamical gauge configurations generated with two flavours of Wilson fermions at beta = 5.6. These results, the first of their kind obtained with dynamical Wilson fermions, are compared to a quenched analysis at equivalent lattice spacing, beta = 6.0. Using our three sea-quark values we perform the ``chiral'' extrapolation to m_eff = m_s/3, where m_s denotes the strange quark mass. The light quark mass dependence is found to be small in relation to the statistical errors. Comparing the full QCD result to our quenched simulation we find better agreement of our dynamical data with experimental results in the spin-independent sector but observe no unquenching effects in hyperfine-splittings. To pin down the systematic errors we have also compared quenched results in different ``tadpole'' schemes as well as using a lower order action. We find that spin-splittings with an O(M_bv^4) action are O(10%) higher compared to O(M_bv^6) results. Relative to the results obtained with the plaquette method the Landau gauge mean link tadpole scheme raises the spin splittings by about the same margin so that our two improvements are opposite in effect.Comment: 24 pages (latex file, Phys Rev D style file, uses epsf-style

Monopoles at Finite Volume and Temperature in SU(2) Lattice Gauge Theory

We resolve a discrepancy between the SU(2) spacial string tension at finite temperature, and the value obtained by monopoles in the maximum Abelian gauge. Previous work had incorrectly omitted a term due to Dirac sheets. When this term is included, the monopole and full SU(2) determinations of the spacial string tension agree to within the statistical errors of the monopole calculation.Comment: 8 pages, Latex files: msum.tex,msum.aux packaged with uufile

Bottomonium from NRQCD with Dynamical Wilson Fermions

We present results for the b \bar b spectrum obtained using an O(M_bv^6)-correct non-relativistic lattice QCD action. Propagators are evaluated on SESAM's three sets of dynamical gauge configurations generated with two flavours of Wilson fermions at beta = 5.6. Compared to a quenched simulation at equivalent lattice spacing we find better agreement of our dynamical data with experimental results in the spin-independent sector but observe no unquenching effects in hyperfine-splittings. To pin down the systematic errors we have also compared quenched results in different ``tadpole'' schemes and used a lower order action.Comment: Talk presented at LATTICE'97, 3 pages, Late

The Spatial String Tension in the Deconfined Phase of the (3+1)-Dimensional SU(2) Gauge Theory

We present results of a detailed investigation of the temperature dependence of the spatial string tension in SU(2) gauge theory. We show, for the first time, that the spatial string tension is scaling on the lattice and thus is non-vanishing in the continuum limit. It is temperature independent below Tc and rises rapidly above. For temperatures larger than 2Tc we find a scaling behaviour consistent with sigma_s(T) = 0.136(11) g^4(T) T^2, where g(T) is the 2-loop running coupling constant with a scale parameter determined as Lambda_T = 0.076(13) Tc.Comment: 8 pages (Latex, shell archive, 3 PostScript figures), HLRZ-93-43, BI-TP 93/30, FSU-SCRI-93-76, WUB 93-2

Adjoint Wilson Line in SU(2) Lattice Gauge Theory

The behavior of the adjoint Wilson line in finite-temperature, $SU(2)$, lattice gauge theory is discussed. The expectation value of the line and the associated excess free energy reveal the response of the finite-temperature gauge field to the presence of an adjoint source. The value of the adjoint line at the critical point of the deconfining phase transition is highlighted. This is not calculable in weak or strong coupling. It receives contributions from all scales and is nonanalytic at the critical point. We determine the general form of the free energy. It includes a linearly divergent term that is perturbative in the bare coupling and a finite, nonperturbative piece. We use a simple flux tube model to estimate the value of the nonperturbative piece. This provides the normalization needed to estimate the behavior of the line as one moves along the critical curve into the weak coupling region.Comment: 21 pages, no figures, Latex/Revtex 3, UCD-93-1

A novel probe of the vacuum of the lattice gluodynamics

We introduce a notion of minimal number of negative links on the lattice for a given original configuration of SU(2) fields. Negative links correspond to a large potential, not necessarily large action. The idea is that the minimal number of negative links is a gauge invariant notion. To check this hypothesis we measure correlator of two negative links, averaged over all the directions, as function of the distance between the links. The inverse correlation length coincides within the error bars with the lightest glueball mass.Comment: 6 pages, 2 figure

Block Spin Effective Action for 4d SU(2) Finite Temperature Lattice Gauge Theory

The Svetitsky-Yaffe conjecture for finite temperature 4d SU(2) lattice gauge theory is confirmed by observing matching of block spin effective actions of the gauge model with those of the 3d Ising model. The effective action for the gauge model is defined by blocking the signs of the Polyakov loops with the majority rule. To compute it numerically, we apply a variant of the IMCRG method of Gupta and Cordery.Comment: LaTeX2e, 22 pages, 8 Figure

Computation of the Vortex Free Energy in SU(2) Gauge Theory

We present the first measurement of the vortex free-energy order parameter at weak coupling for SU(2) in simulations employing multihistogram methods. The result shows that the excitation probability for a sufficiently thick vortex in the vacuum tends to unity. This is rigorously known to provide a necessary and sufficient condition for maintaining confinement at weak coupling in SU(N) gauge theories.Comment: 7 pages, LaTeX with 3 eps figures, minor changes, replacement of Fig.