Tue·Nov 8, 2005Tuesday·November 8, 2005

1. 01*

   Improved bilinears in lattice QCD with non-degenerate quarks

   Tanmoy Bhattacharya🇺🇸 · Rajan Gupta🇺🇸 · Weonjong Lee🇰🇷 · Stephen R. Sharpe🇺🇸 · Jackson M. S. Wu🇺🇸

   We describe the extension of the improvement program for bilinear operators composed of Wilson fermions to non-degenerate dynamical quarks. We consider two, three and four flavors, and both flavor non-singlet and singlet operators. We find that there are many more improvement coefficients than with degenerate quarks, but that, for three or four flavors, nearly all can be determined by enforcing vector and axial Ward identities. The situation is worse for two flavors, where many more coefficients remain undetermined.

   hep-latPRD(2006)·137 citations
2. 02*

   Estimate of the charmed 0-- hybrid meson spectrum from quenched lattice QCD

   Yan Liu🇨🇳 · Xiang-Qian Luo (Zhongshan Univ.)🇨🇳

   We compute from quenched lattice QCD the ground state masses of the charmed hybrid mesons cbar c g, with exotic quantum numbers JPC=1-+, 0+- and 0--. The 0-- hybrid meson spectrum has never been provided by lattice simulations due to the difficulties to extract high gluonic excitations from noise. We employ improved gauge and fermion actions on the anisotropic lattice, which reduce greatly the lattice artifacts, and lead to very good signals. The data are extrapolated to the continuum limit, with finite size effects under well control. For 1-+ and 0+- hybrid mesons, the ground state masses are 4.405(38) GeV and 4.714(52) GeV. We predict for the first time from lattice QCD, the ground state mass of 0-- to be 5.883(146) GeV.

   hep-lathep-exhep-phPRD(2006)·33 citations
3. 03*

   Exploring Topology Conserving Gauge Actions for Lattice QCD

   W. Bietenholz🇩🇪 · K. Jansen🇩🇪 · K.-I. Nagai🇩🇪 · S. Necco🇫🇷 · L. Scorzato🇩🇪 · S. Shcheredin🇩🇪

   We explore gauge actions for lattice QCD, which are constructed such that the occurrence of small plaquette values is strongly suppressed. By choosing strong bare gauge couplings we arrive at values for the physical lattice spacings of O(0.1 fm). Such gauge actions tend to confine the Monte Carlo history to a single topological sector. This topological stability facilitates the collection of a large set of configurations in a specific sector, which is profitable for numerical studies in the epsilon-regime. The suppression of small plaquette values is also expected to be favourable for simulations with dynamical quarks. We use a local Hybrid Monte Carlo algorithm to simulate such actions, and we present numerical results for the static potential, the physical scale, the topological stability and the kernel condition number of the overlap Dirac operator. In addition we discuss the question of reflection positivity for a class of such gauge actions.

   hep-latJHEP(2006)·31 citations
4. 04*

   Order, Disorder and Confinement

   M. D'Elia🇮🇹 · A. Di Giacomo🇮🇹 · C. Pica🇮🇹

   Studying the order of the chiral transition for $N_f=2$ is of fundamental importance to understand the mechanism of color confinement. We present results of a numerical investigation on the order of the transition by use of a novel strategy in finite size scaling analysis. The specific heat and a number of susceptibilities are compared with the possible critical behaviours. A second order transition in the O(4) and O(2) universality classes are excluded. Substantial evidence emerges for a first order transition. Results are in agreement with those found by studying the scaling properties of a disorder parameter related to the dual superconductivity mechanism of color confinement.

   hep-latAIP Conf.Proc.(2006)·0 citations
5. 05*

   Study of color superconductivity with Ginzburg-Landau effective action on the lattice

   Sanatan Digal🇯🇵 · Tetsuo Hatsuda🇯🇵 · Munehisa Ohtani🇯🇵

   We study thermal phase transitions of color superconductivity by the lattice simulations of the Ginzburg-Landau (GL) effective theory. The theory is equivalent to the SU_ f(3) cross SU_c(3) Higgs model coupled to SU_c(3) color gauge fields. From the eigenvalues of a 3-by-3 gauge-invariant diquark composite, a clear distinction between the 2-flavor color superconductivity (2SC) and the color flavor locking (CFL) phase is made in a gauge invariant manner. The thermal transitions between the normal phase and the superconducting phases are found to be first-order due to thermal gluons. The phase structure in the coupling-constant space is numerically explored and three patterns of phase transition, i.e., normal to 2SC, normal to CFL and normal to CFL via 2SC, are found in the chiral limit. These results agree qualitatively with the weak-coupling analysis of the GL theory.

   hep-lathep-phnucl-th2 citations
6. 06*

   Effective Lattice Actions for Finite-Temperature Yang-Mills Theory

   Thomas Heinzl🇬🇧 · Tobias Kaestner🇩🇪 · Andreas Wipf🇩🇪

   We determine effective lattice actions for the Polyakov loop using inverse Monte Carlo techniques.

   hep-lat0 citations
7. 07*

   Chiral Extrapolation of Lattice Data for Heavy Meson Hyperfine Splittings

   X.-H. Guo🇨🇳 · P.C. Tandy🇺🇸 · A.W. Thomas🇺🇸

   We investigate the chiral extrapolation of the lattice data for the light-heavy meson hyperfine splittings D^*-D and B^*-B to the physical region for the light quark mass. The chiral loop corrections providing non-analytic behavior in m_\pi are consistent with chiral perturbation theory for heavy mesons. Since chiral loop corrections tend to decrease the already too low splittings obtained from linear extrapolation, we investigate two models to guide the form of the analytic background behavior: the constituent quark potential model, and the covariant model of QCD based on the ladder-rainbow truncation of the Dyson-Schwinger equations. The extrapolated hyperfine splittings remain clearly below the experimental values even allowing for the model dependence in the description of the analytic background.

   hep-lathep-phnucl-thFew Body Syst.(2006)·1 citation
8. 08*

   Universality and Quark Masses of the Staggered Fermion Action

   Anna Hasenfratz🇺🇸

   Staggered fermions with 4 tastes are expected to describe 4-flavor QCD in the continuum limit, therefore at finite lattice spacing the staggered determinant should be equivalent to an SU(4) flavor-symmetric system up to lattice artifacts. This equivalence is the starting point of the 4th root trick used to reduce the number of fermion flavors and provides the only consistent description of 2 or 1 flavor systems. In this paper we argue that the quark mass of the underlying flavor symmetric theory differs from the staggered mass by an additive term due to the taste breaking of the staggered action. The relation is the same for 2 and 1 flavor fermions. This additive mass shift implies that at finite lattice spacing staggered simulations correspond to heavier quark masses than indicated by the staggered Goldstone pion and that staggered fermions cannot reach the chiral limit at finite lattice spacing.

   hep-lat8 citations
9. 09*

   PQChPT with Staggered Sea and Valence Ginsparg-Wilson Quarks: Vector Meson Masses

   Hovhannes R. Grigoryan🇺🇸 · Anthony W. Thomas🇺🇸

   We consider partially quenched, mixed chiral perturbation theory with staggered sea and Ginsparg-Wilson valence quarks in order to extract a chiral-continuum extrapolation expression for the vector meson mass up to order O(a^2), at one-loop level. Based on general principles, we accomplish the task without explicitly constructing a sophisticated, heavy vector meson chiral Lagrangian.

   hep-latJ.Phys.G(2005)·0 citations
10. 10*

    Non-Perturbative Gluon pair production from a Constant Chromo-Electric Field via the Schwinger Mechanism in Arbitrary Gauge

    Fred Cooper (Santa Fe Inst.)🇺🇸 · Gouranga C. Nayak (SUNY, Stony Brook)🇺🇸

    We study the non-perturbative production of gluon pairs from a constant SU(3) chromo-electric background field via the Schwinger mechanism. We fix the covariant background gauge with an arbitrary gauge parameter \alpha. We determine the transverse momentum distribution of the gluons, as well as the total probability of creating pairs per unit space time volume. We find that the result is independent of the covariant gauge parameter \alpha used to define arbitrary covariant background gauges. We find that our non-perturbative result is both gauge invariant and gauge parameter \alpha independent.

    ↳ hep-phhep-lathep-thnucl-thPRD(2006)·69 citations
11. 11*

    Phase transition in the Higgs model of scalar dyons

    C.R. Das🇮🇳 · L.V. Laperashvili🇷🇺

    In the present paper we investigate the phase transition "Coulomb--confinement" in the Higgs model of abelian scalar dyons -- particles having both, electric $e$ and magnetic $g$, charges. It is shown that by dual symmetry this theory is equivalent to scalar fields with the effective squared electric charge e^{*2}=e^2+g^2. But the Dirac relation distinguishes the electric and magnetic charges of dyons. The following phase transition couplings are obtained in the one--loop approximation: \alpha_{crit}=e^2_{crit}/4\pi\approx 0.19, \tilde\alpha_{crit}=g^2_{crit}/4\pi\approx 1.29 and \alpha^*_{crit}\approx 1.48.

    ↳ hep-phhep-lathep-thMod.Phys.Lett.A(2006)·2 citations
12. 12*

    Strong to weak coupling transitions of SU(N) gauge theories in 2+1 dimensions

    Francis Bursa🇬🇧 · Michael Teper🇬🇧

    We investigate strong-to-weak coupling transitions in D=2+1 SU(N->oo) gauge theories, by simulating lattice theories with a Wilson plaquette action. We find that there is a strong-to-weak coupling cross-over in the lattice theory that appears to become a third-order phase transition at N=oo, in a manner that is essentially identical to the Gross-Witten transition in the D=1+1 SU(oo) lattice gauge theory. There is also evidence for a second order transition at N=oo at approximately the same coupling, which is connected with centre monopoles (instantons) and so analogues to the first order bulk transition that occurs in D=3+1 lattice gauge theories for N>4. We show that as the lattice spacing is reduced, the N=oo gauge theory on a finite 3-torus suffers a sequence of (apparently) first-order ZN symmetry breaking transitions associated with each of the tori (ordered by size). We discuss how these transitions can be understood in terms of a sequence of deconfining transitions on ever-more dimensionally reduced gauge theories.We investigate whether the trace of the Wilson loop has a non-analyticity in the coupling at some critical area, but find no evidence for this although, just as in D=1+1,the eigenvalue density of a Wilson loop forms a gap at N=oo for a critical trace. The physical implications of this are unclear.The gap formation is a special case of a remarkable similarity between the eigenvalue spectra of Wilson loops in D=1+1 and D=2+1 (and indeed D=3+1): for the same value of the trace, the eigenvalue spectra are nearly identical.This holds for finite as well as infinite N; irrespective of the Wilson loop size in lattice units; and for Polyakov as well as Wilson loops.

    ↳ hep-thhep-latPRD(2006)·26 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.