PaperPanorama

HEP Lattice·hep-lat

Fri·Oct 19, 2001

12 papers—10 primary·2 cross-listed·reconstructed*

All12Primary10Cross-lists2
  1. 01*

    The monopole mass in the three-dimensional Georgi-Glashow model

    A.C. Davis🇬🇧 · A. Hart🇬🇧 · T.W.B. Kibble🇬🇧 · A. Rajantie🇬🇧

    We study the three-dimensional Georgi-Glashow model to demonstrate how magnetic monopoles can be studied fully non-perturbatively in lattice Monte Carlo simulations, without any assumptions about the smoothness of the field configurations. We examine the apparent contradiction between the conjectured analytic connection of the `broken' and `symmetric' phases, and the interpretation of the mass (i.e., the free energy) of the fully quantised 't Hooft-Polyakov monopole as an order parameter to distinguish the phases. We use Monte Carlo simulations to measure the monopole free energy and its first derivative with respect to the scalar mass. On small volumes we compare this to semi-classical predictions for the monopole. On large volumes we show that the free energy is screened to zero, signalling the formation of a confining monopole condensate. This screening does not allow the monopole mass to be interpreted as an order parameter, resolving the paradox.

    hep-latastro-phhep-thPRD(2002)·24 citations
  2. 02*

    The Consequences of Non-Normality

    I. Hip🇩🇪 · Th. Lippert🇩🇪 · H. Neff🇩🇪 · K. Schilling🇩🇪 · W. Schroers🇩🇪

    The non-normality of Wilson-type lattice Dirac operators has important consequences - the application of the usual concepts from the textbook (hermitian) quantum mechanics should be reconsidered. This includes an appropriate definition of observables and the refinement of computational tools. We show that the truncated singular value expansion is the optimal approximation to the inverse operator D^{-1} and we prove that due to the gamma_5-hermiticity it is equivalent to gamma_5 times the truncated eigenmode expansion of the hermitian Wilson-Dirac operator.

    hep-latNucl.Phys.B Proc.Suppl.(2002)·11 citations
  3. 03*

    Simulating dynamical fermions with smeared links

    A. Hasenfratz🇺🇸 · F. Knechtli (U. of Colorado)🇺🇸

    Smearing the gauge links of dynamical configurations removes small scale unphysical vacuum fluctuations and thus improves the chiral properties of lattice fermions. Recently we proposed the hypercubic smearing (HYP) that improves the flavor symmetry of staggered fermions by an order of magnitude with only minimal distortions at small distances. We describe a new algorithm to simulate dynamical HYP fermions based on the standard pure gauge overrelaxation and heatbath updates. The algorithm has been used to simulate four and two flavors of staggered fermions. Unlike standard dynamical simulation techniques, this algorithm does not loose efficiency at small quark masses.

    hep-latNucl.Phys.B Proc.Suppl.(2002)·6 citations
  4. 04*

    The QCD String Spectrum and Conformal Field Theory

    K.J. Juge🇺🇸 · J. Kuti🇺🇸 · C.J. Morningstar🇺🇸

    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.

    hep-latNucl.Phys.B Proc.Suppl.(2002)·13 citations
  5. 05*

    Exploiting finite-size-effects to simulate full QCD with light quarks - a progress report

    B. Orth🇩🇪 · N. Eicker🇩🇪 · Th. Lippert🇩🇪 · K. Schilling🇩🇪 · W. Schroers🇩🇪 · Z. Sroczynski🇩🇪

    We present a report on the status of the GRAL project (Going Realistic And Light), which aims at simulating full QCD with two dynamical Wilson quarks below the vector meson decay threshold, m_ps/m_v < 0.5, making use of finite-size-scaling techniques.

    hep-latNucl.Phys.B Proc.Suppl.(2002)·5 citations
  6. 06*

    A nonperturbative determination of the O(a) improvement coefficient c_A and the scaling of f_pi and m^{MSbar}

    S. Collins🇬🇧 · C. T. H. Davies🇬🇧 · G. P. Lepage🇺🇸 · J. Shigemitsu🇺🇸

    We report on an investigation of the LANL method for determining the O(a) improvement coefficient c_A nonperturbatively. We find we are able to extract reliable estimates for the coefficient using this method. However, our study of systematic errors shows that for very accurate determinations of c_A, the smearing function must be tuned and the volume fixed to keep the O(a) ambiguity in c_A fixed as beta varies. Consistency was found with previous results from the LANL group and (within fairly large errors) 1-loop perturbation theory; c_A does not change significantly over the range beta=5.93-6.2. The big difference between our results and those of the ALPHA collaboration, around beta=6.0, show that the O(a) differences in c_A between the different methods can be large. We find that the lattice spacing dependence of f_pi and the renormalised quark mass is much smaller using our values of the coefficient compared to those of the ALPHA collaboration.

    hep-latPRD(2003)·14 citations
  7. 07*

    Bound states in the 3d Ising model and implications for QCD at finite temperature and density

    M.Caselle🇮🇹 · M.Hasenbusch🇩🇪 · P.Provero🇮🇹 · K.Zarembo🇸🇪

    We study the spectrum of bound states of the three dimensional Ising model in the (h,beta) plane near the critical point. We show the existence of an unbinding line, defined as the boundary of the region where bound states exist. Numerical evidence suggests that this line coincides with the beta=beta_c axis. When the 3D Ising model is considered as an effective description of hot QCD at finite density, we conjecture the correspondence between the unbinding line and the line that separates the quark-gluon plasma phase from the superconducting phase. The bound states of the Ising model are conjectured to correspond to the diquarks of the latter phase of QCD.

    hep-latNucl.Phys.B Proc.Suppl.(2002)·4 citations
  8. 08*

    Heavy-light physics using NRQCD-staggered actions

    Matthew Wingate🇺🇸 · Junko Shigemitsu🇺🇸 · G. Peter Lepage🇺🇸

    One leading source of uncertainty in the lattice computation of semi-leptonic form factors in B decay, and to a lesser extent B meson decay constants, comes from the extrapolation of the light quark mass to the physical up/down mass. This talk presents first explorations of simulating the light quark with staggered fermion actions, which are free of the spurious zero modes that effect Wilson-like Dirac operators and are less costly. Methods for fitting to Euclidean-time NRQCD-staggered meson propagators are discussed, and some preliminary spectrum results are presented.

    hep-latNucl.Phys.B Proc.Suppl.(2002)·3 citations
  9. 09*

    Monopoles and hybrids in Abelian projection of lattice QCD

    P. Yu. Boyko🇷🇺 · M. N. Chernodub🇷🇺 · A. V. Kovalenko🇷🇺 · S. M. Morozov🇷🇺 · M.I. Polikarpov🇷🇺

    We study topological defects constructed from diagonal and non-diagonal gluons in Abelian projection of zero temperature lattice QCD. We compare results obtained in the quenched and non-quenched vacuum field configurations and show that the density of hybrids is higher than the density of monopoles. The density of some hybrids is sensitive to the presence of the virtual fermions.

    hep-lathep-phNucl.Phys.B Proc.Suppl.(2002)·0 citations
  10. 10*

    Spectral density calculations in a heavy-light meson-meson system

    LHPC · H. Rudolf Fiebig (FIU)

    A system of two static quarks, at fixed distances r, and two light quarks is studied on an anisotropic lattice. Excitations by operators emphasizing quark or gluon degrees of freedom are examined. The maximum entropy method is applied in the spectral analysis. These simulations ultimately aim at learning about mechanisms of hadronic interaction.

    hep-latNucl.Phys.B Proc.Suppl.(2002)·5 citations
  11. 11*

    Lattice calculation of the zero-recoil form factor of anti-B --> D* lepton anti-neutrino: toward a model independent determination of |V(cb)|

    Shoji Hashimoto🇯🇵 · Andreas S. Kronfeld🇺🇸 · Paul B. Mackenzie🇺🇸 · Sinead M. Ryan🇮🇪 · James N. Simone🇺🇸

    We develop a new method in lattice QCD to calculate the form factor F(1) at zero recoil. This is the main theoretical ingredient needed to determine |V(cb)| from the exclusive decay anti-B --> D* lepton anti-neutrino. We introduce three ratios, in which most of statistical and systematic error cancels, making a precise calculation possible. We fit the heavy-quark mass dependence directly, and extract the 1/m_Q^2 and three of the four 1/m_Q^3 corrections in the heavy-quark expansion. In this paper we show how the method works in the quenched approximation, obtaining F(1) = 0.913 (+0.024-0.017)(+/-0.016)(+0.003-0.014)(+0.000-0.016)(+0.006-0.014) where the uncertainties come, respectively, from statistics and fitting, matching lattice gauge theory to QCD, lattice spacing dependence, light quark mass effects, and the quenched approximation. We also discuss how to reduce these uncertainties and, thus, to obtain a model-independent determination of |V(cb)|.

    ↳ hep-phhep-latPRD(2002)·160 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.