Strong Coupling Model for String Breaking on the Lattice

A model for SU(n) string breaking on the lattice is formulated using strong coupling ideas. Although necessarily rather crude, the model gives an explicit picture of string breaking in the presence of dynamical quarks as a mixing phenomenon that involves the string state and a two-meson state. A careful analysis, within the model, of the Wilson loop shows that the evolution of the mixing angle as a function of separation may obscure the expected crossover effect. If a sufficiently extensive mixing region exists then an appropriate combination of transition amplitudes can help in revealing the effect. The sensitivity of the mixing region to the values of the meson energy and the dynamical quark mass is explored and an assessment made of the dectectibility of string breaking in a practical lattice simulation.Comment: 14 pages, LATEX2e, 2 figures, uses styles[12pt,a4,epsf

Mixing Scenarios for Lattice String Breaking

We present some simple scenarios for string breaking on the lattice based on a crude strong coupling model introduced previously. We review the dependence of the model on lattice spacing and extend it to include degenerate dynamical quarks and also meson exchange diagrams. A comparison is made between quenched and unquenched calculations. We examine string breaking in the presence of a static quark-diquark system, a situation that is specific to SU(3).Comment: 15 pages 5 fig

Spherical Formulation for Diagramatic Evaluations on a Manifold with Boundary

The mathematical formalism necessary for the diagramatic evaluation of quantum corrections to a conformally invariant field theory for a self-interacting scalar field on a curved manifold with boundary is considered. The evaluation of quantum corrections to the effective action past one-loop necessitates diagramatic techniques. Diagramatic evaluations and higher loop-order renormalisation can be best accomplished on a Riemannian manifold of constant curvature accommodating a boundary of constant extrinsic curvature. In such a context the stated evaluations can be accomplished through a consistent interpretation of the Feynman rules within the spherical formulation of the theory for which the method of images allows. To this effect, the mathematical consequences of such an interpretation are analyzed and the spherical formulation of the Feynman rules on the bounded manifold is, as a result, developed.Comment: 12 pages, references added. To appear in Classical and Quantum Gravit

The contribution of O(alpha) radiative corrections to the renormalised anisotropy and application to general tadpole improvement schemes: addendum to "One loop calculation of the renormalised anisotropy for improved anisotropic gluon actions on a lattice" [hep-lat/0208010]

General O(alpha) radiative corrections to lattice actions may be interpreted as counterterms that give additive contributions to the one-loop renormalisation of the anisotropy. The effect of changing the radiative coefficients is thus easily calculable. In particular, the results obtained in a previous paper for Landau mean link improved actions apply in any tadpole improvement scheme. We explain how this method can be exploited when tuning radiatively improved actions. Efficient methods for self-consistently tuning tadpole improvement factors are also discussed.Comment: 3 pages of revte

Effective diffusion constant in a two dimensional medium of charged point scatterers

We obtain exact results for the effective diffusion constant of a two dimensional Langevin tracer particle in the force field generated by charged point scatterers with quenched positions. We show that if the point scatterers have a screened Coulomb (Yukawa) potential and are uniformly and independently distributed then the effective diffusion constant obeys the Volgel-Fulcher-Tammann law where it vanishes. Exact results are also obtained for pure Coulomb scatterers frozen in an equilibrium configuration of the same temperature as that of the tracer.Comment: 9 pages IOP LaTex, no figure