The Casimir Energy Paradox of the QCD String

It is widely thought that the early onset of the asymptotic Casimir energy with unit conformal charge signals bosonic string formation of the confining flux connecting a static quark-antiquark pair in QCD. This is observed on a scale where most of the string eigenmodes do not exist and the few stable modes above the ground state are displaced. Hints for the resolution of this paradox are suggested.Comment: Lattice2003(topology

Excitations of the static quark-antiquark system in several gauge theories

The spectrum of gluons in the presence of a static quark-antiquark pair is studied using Monte Carlo simulations on anisotropic space-time lattices. For very small quark-antiquark separations R, the level orderings and approximate degeneracies disagree with the expectations from an effective string theory. As the quark-antiquark separation R increases, a dramatic rearrangement of the energies occurs, and above 2 fm, all of the levels studied show behavior consistent with an effective string description. The energy spacings are nearly pi/R, but a tantalizing fine structure remains. In addition to 4-dimensional SU(3) gauge theory, results from 3-dimensional SU(2) and compact U(1) gauge theories are also presented.Comment: 12 pages, 4 figures, talk presented at the International Conference on Color Confinement and Hadrons in Quantum Chromodynamics (Confinement 2003), RIKEN, July 21-24, 200

The heavy-quark hybrid meson spectrum in lattice QCD

Recent findings on the spectrum of heavy-quark mesons from computer simulations of quarks and gluons in lattice QCD are summarized, with particular attention to quark-antiquark states bound by an excited gluon field. The validity of a Born-Oppenheimer treatment for such systems is discussed. Recent results on glueball masses, the light-quark 1-+ hybrid meson mass, and the static three-quark potential are summarized.Comment: 15 pages, 13 figures, talk given at the Workshop on Scalar Mesons: An Interesting Puzzle for QCD, SUNY Institute of Technology, Utica, NY, May 16-18, 2003, submitted to American Institute of Physics Conference Proceedings. After publication, it will be found at http://proceedings.aip.org/proceedings

The QCD String Spectrum and Conformal Field Theory

The low energy excitation spectrum of the critical Wilson surface is discussed between the roughening transition and the continuum limit of lattice QCD. The fine structure of the spectrum is interpreted within the framework of two-dimensional conformal field theory.Comment: Lattice2001 (confinement),3 pages,1 figure,uses espcrc2.st

QCD String Spectrum 2002

Results from a comprehensive new analysis on the excitation spectrum of the QCD string are presented. A rapid onset of string formation is observed in the spectrum on a length scale of 2 fm, with Dirichlet boundary conditions. The crossover from the short distance spectrum towards string excitations and an observed fine structure in the 1--3 fm range are related to effective string theory. The deficiencies of the Nambu-Goto bosonic string model in describing the observed spectrum are briefly discussed.Comment: Lattice2002(topology), 3 pages, 2 figure

Coulomb energy and gluon distribution in the presence of static sources

We compute the energy of the ground state and a low lying excitation of the gluonic field in the presence of static quark -anti-quark (\qq) sources. We show that for separation between the sources less then a few fm the gluonic ground state of the static \qq system can be well described in terms of a mean field wave functional with the excited states corresponding to a single quasi-particle excitation of the gluon field. We also discuss the role of many particle excitations relevant for large separation between sources.Comment: 14 pages, 11 figure