The Running Coupling from SU(3) Gauge Theory

We present high precision results on the static quark-antiquark-potential on 32^4 and smaller lattices, using the standard Wilson action at BETA = 6.0, 6.2, 6.4, and 6.8 on the Connection Machine CM-2. Within our statistical errors (1%) we did not observe any finite size effects affecting the potential values, on varying the spatial lattice extent from 0.9 fm up to 3.3 fm. We find violations of asymptotic scaling in the bare coupling up to BETA = 6.8. We demonstrate that scaling violations on the string tension can be considerably reduced by introducing effective coupling schemes, which allow for a safer extrapolation of LAMBDA_Lattice to its continuum value. We are also able to see and to quantify the running of the coupling from the interquark force. From this we extract the ratio \sqrt{SIGMA}/LAMBDA_L. Both methods yield consistent values for the LAMBDA-parameter: LAMBDA_MSbar = 0.558(-0.007+0.017)\sqrt{SIGMA} = 246(-3+7) MeV.Comment: (Talk G. Bali at Lattice 92, Amsterdam), 4 Pages, 4 Postscript figures, LaTeX with espcrc2, and epsf style file

String breaking

We numerically investigate the transition of the static quark-antiquark string into a static-light meson-antimeson system. Improving noise reduction techniques, we are able to resolve the signature of string breaking dynamics for Nf=2 lattice QCD at zero temperature. We discuss the lattice techniques used and present results on energy levels and mixing angle of the static two-state system. We visualize the action density distribution in the region of string breaking as a function of the static colour source-antisource separation. The results can be related to properties of quarkonium systems.Comment: 8 pages, Talk given at the Workshop on Computational Hadron Physics, Nicosia, Cyprus, 14--17 September 200

A Ginzburg-Landau Analysis of the Colour Electric Flux Tube

In a simulation of SU(2) gauge theory we investigate, after maximal Abelian projection, the dual Maxwell equations for colour field and monopole current distributions around a static quark-antiquark pair Q_ Q in vacuo. Within the dual superconductor picture we carry out a Ginzburg-Landau type analysis of the flux tube profile. As a result we can determine the coherence length of the GL wave function related to the monopole condensate, xi = .25(3) fm, to be compared to the penetration length, lambda = >.15(2) fm (scaled with the string tension).Comment: 3 pages, 5 figures, corrected typos, LATTICE98(confine

Color Flux Profiles in SU(2) Lattice Gauge Theory

Results of a high statistics study of chromo field distributions around static sources in pure SU(2) gauge theory on lattices of volumes $16^4$, $32^4$, and $48^3\times 64$ at $\beta=2.5$, $2.635$, and $2.74$ are presented. We establish string formation up to physical distances as large as 2 fm.Comment: Contribution to Lattice '94, 3 pages uu-compressed LaTeX + 3 psfig

Towards the glueball spectrum of full QCD

We present first results on masses of the scalar and tensor glueballs as well as of the torelon from simulations of QCD with two light flavours of Wilson fermions. The gauge configurations of extent 16^3*32 at beta = 5.6 and kappa = 0.156, 0.157 and 0.1575 have been generated as part of the SESAM collaboration programme. The present lattice resolutions correspond to 1/a = 2.0-2.3 GeV and ratios m(pi)/m(rho) = 0.83, 0.76 and 0.71, respectively. Studies on larger lattice volumes and closer to the chiral limit are in progress.Comment: 4 pages, LaTeX, espcrc2 and epsf styles required, 4 epsf figures, poster presented by G. Bali at Lattice '9

A comprehensive lattice study of SU(3) glueballs

We present a study of the $SU(3)$ glueball spectrum for all $J^{PC}$ values at lattice spacings down to $a^{-1}=3.73 (6)$ GeV ($\beta=6.4$) using lattices of size up to $32^4$. We extend previous studies and show that the continuum limit has effectively been reached. The number of clearly identified $J^{PC}$ states has been substantially increased. There are no clear signals for spin-exotic glueballs below 3 GeV. A comparison with current experimental glueball candidates is made.Comment: 10 pages including 2 PS figures, Liverpool Preprint: LTH 303, Wuppertal Preprint: WUB 93-1