Fri·Oct 18, 2002Friday·October 18, 2002

1. 01*

   Moments of Isovector Quark Distributions in Lattice QCD

   W. Detmold🇺🇸 · W. Melnitchouk🇺🇸 · A.W. Thomas🇦🇺

   We investigate the connection of lattice calculations of moments of isovector parton distributions to the physical regime through extrapolations in the quark mass. We consider the one pion loop renormalisation of the nucleon matrix elements of the corresponding operators and thereby develop formulae with which to extrapolate the moments of the unpolarised, helicity and transversity distributions. These formulae are consistent with chiral perturbation theory in the chiral limit and incorporate the correct heavy quark limits. In the polarised cases, the inclusion of intermediate states involving the $\Delta$ isobar is found to be very important. The results of our extrapolations are in general agreement with the phenomenological values of these moments where they are known, and for the first time we perform an extrapolation of the low moments of the isovector transversity distribution which is consistent with chiral symmetry.

   hep-latEPJC(2003)·4 citations
2. 02*

   Excited charmonium spectrum from anisotropic lattices

   X. Liao🇺🇸 · T. Manke🇺🇸

   We present our final results for the excited charmonium spectrum from a quenched calculation using a fully relativistic anisotropic lattice QCD action. A detailed excited charmonium spectrum is obtained, including both the exotic hybrids (with $J^{PC}=1^{-+},0^{+-},2^{+-}$) and orbitally excited mesons (with orbital angular momentum up to 3). Using three different lattice spacings (0.197, 0.131, and 0.092 fm), we perform a continuum extrapolation of the spectrum. We convert our results in lattice units to physical values using lattice scales set by the ${}^1{P}_1-1S$ splitting. The lowest lying exotic hybrid $1^{-+}$ lies at 4.428(41) GeV, slightly above the $D^{\ast \ast }D$ (S+P wave) threshold of 4.287 GeV. Another two exotic hybrids $0^{+-}$ and $2^{+-}$ are determined to be 4.70(17) GeV and 4.895(88) GeV, respectively. Our finite volume analysis confirms that our lattices are large enough to accommodate all the excited states reported here.

   hep-lat106 citations
3. 03*

   Hamiltonian lattice quantum chromodynamics at finite density with Wilson fermions

   Yi-Zhong Fang🇨🇳 · Xiang-Qian Luo (Corresponding Author, Zhongshan Univ., China)🇨🇳

   Quantum chromodynamics (QCD) at sufficiently high density is expected to undergo a chiral phase transition. Understanding such a transition is of particular importance for neutron star or quark star physics. In Lagrangian SU(3) lattice gauge theory, the standard approach breaks down at large chemical potential $\mu$, due to the complex action problem. The Hamiltonian formulation of lattice QCD doesn't encounter such a problem. In a previous work, we developed a Hamiltonian approach at finite chemical potential $\mu$ and obtained reasonable results in the strong coupling regime. In this paper, we extend the previous work to Wilson fermions. We study the chiral behavior and calculate the vacuum energy, chiral condensate and quark number density, as well as the masses of light hadrons. There is a first order chiral phase transition at zero temperature.

   hep-lathep-phPRD(2004)·17 citations
4. 04*

   Percolating cluster of center vortices and confinement

   F. Gliozzi🇮🇹 · M. Panero🇮🇹 · P. Provero🇮🇹

   We study the role of percolating clusters of center vortices in configurations of an Ising gauge theory in 3D. It is known that low energy features of gauge theories can be described in terms of an ``effective string picture'', and that confinement properties are associated with topologically non-trivial configurations. We focus our attention upon percolating clusters of center vortices, and present numerical evidence for the fact that these objects play a preminent role in confinement phenomenon, since their removal sweeps off confinement altogether. Moreover, numerical simulations show that the string fluctuations, and in particular the Luescher term, are completely encoded in the percolating cluster.

   hep-latNucl.Phys.B Proc.Suppl.(2003)·0 citations
5. 05*

   Lattice Models with N=2 Supersymmetry

   Paul Fendley🇺🇸 · Kareljan Schoutens🇳🇱 · Jan de Boer🇳🇱

   We introduce lattice models with explicit N=2 supersymmetry. In these interacting models, the supersymmetry generators Q^+ and Q^- yield the Hamiltonian H={Q^+,Q^-} on any graph. The degrees of freedom can be described as either fermions with hard cores, or as quantum dimers. The Hamiltonian of our simplest model contains a hopping term and a repulsive potential, as well as the hard-core repulsion. We discuss these models from a variety of perspectives: using a fundamental relation with conformal field theory, via the Bethe ansatz, and using cohomology methods. The simplest model provides a manifestly-supersymmetric lattice regulator for the supersymmetric point of the massless 1+1-dimensional Thirring (Luttinger) model. We discuss the ground-state structure of this same model on more complicated graphs, including a 2-leg ladder, and discuss some generalizations.

   ↳ hep-thcond-mat.stat-mechhep-latPRL(2003)·118 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.