HEP Lattice·hep-lat
12 papers—11 primary·1 cross-listed·reconstructed*
We show how a variant of the Hubbard model can be simulated using a meron-cluster algorithm. This provides a major improvement in our ability to determine the behavior of these types of models. We also present some results that clearly demonstrate the existence of a superconducting state in this model.
Matthew Wingate🇺🇸 · Junko Shigemitsu (Ohio State)🇺🇸 · G. Peter Lepage (Cornell)🇺🇸 · Christine Davies (Glasgow)🇬🇧 · Howard Trottier (Simon Fraser)🇨🇦
Last year we proposed using staggered fermions as the light quarks, combined with nonrelativistic heavy quarks, in simulations of heavy-light mesons. A first round of tests which focuses on the B_s meson has been completed using quenched lattices, and results are presented here for the kinetic B_s mass, the B_s^* - B_s splitting, and f_{B_s}. The next project, already underway, is to compute the B and B_s decay constants and spectra on the n_f = 2+1 and 3 MILC lattices. We report on progress with one set of these configurations.
C. Bernard🇺🇸 · T. Burch🇺🇸 · C. DeTar🇺🇸 · Steven Gottlieb🇺🇸 · E.B. Gregory🇺🇸 · U.M. Heller🇺🇸 · J. Osborn🇺🇸 · R. Sugar🇺🇸 · D. Toussaint🇺🇸
We summarize our measurement of the mass of the exotic hybrid meson using an improved Kogut-Susskind action. We show results from both quenched and dynamical quark simulations and compare with results from Wilson quarks. Extrapolation of these results to the physical quark mass allows comparison with experimental candidates for the hybrid meson.
O. Baer
The spectral flow of the overlap operator is computed numerically along a particular path in gauge field space. The path connects two gauge equivalent configurations which differ by a gauge transformation in the non-trivial class of pi_4(SU(2)). The computation is done with the SU(2) gauge field in the fundamental, the 3/2, and the 5/2 representation. The number of eigenvalue pairs that change places along this path is established for these three representations and an even-odd pattern predicted by Witten is verified.
Christof Gattringer🇩🇪 · Meinulf Göckeler🇩🇪 · Peter Hasenfratz🇨🇭 · Simon Hauswirth🇨🇭 · Kieran Holland🇺🇸 · Thomas Jörg🇨🇭 · K. J. Juge🇨🇭 · C. B. Lang🇦🇹 · Ferenc Niedermayer🇨🇭 · P.E.L. Rakow🇩🇪 · Stefan Schaefer🇩🇪 · Andreas Schäfer (BGR (Bern-Graz-Regensburg) collaboration)🇩🇪
In this contribution we present results from quenched QCD simulations with the parameterized fixed-point (FP) and the chirally improved (CI) Dirac operator. Both these operators are approximate solutions of the Ginsparg-Wilson equation and have good chiral properties. We focus our discussion on observables sensitive to chirality. In particular we explore pion masses down to 210 MeV in light hadron spectroscopy, quenched chiral logs, the pion decay constant and the pion scattering length. We discuss finite volume effects, scaling properties of the FP and CI operators and performance issues in their numerical implementation.
J. Koponen (1)🇫🇮 · A. M. Green (1)🇫🇮 · C. Michael (2)🇬🇧 · P. Pennanen (1) (the UKQCD Collaboration) ((1) University of Helsinki and Helsinki Institute of Physics, Finland, (2) University of Liverpool, UK)🇫🇮
In an earlier work, the charge (vector) and matter (scalar) radial distributions of heavy-light mesons were measured in the quenched approximation on a 16^3 times 24 lattice with a quark-gluon coupling of 5.7, a lattice spacing of 0.17 fm, and a hopping parameter corresponding to a light quark mass about that of the strange quark. Several improvements are now made: 1) The configurations are generated using dynamical fermions with a quark-gluon coupling of 5.2 (a lattice spacing of 0.14 fm); 2) Many more gauge configurations are included (78 compared with the earlier 20); 3) The distributions at many off-axis, in addition to on-axis, points are measured; 4) The data-analysis is much more complete. In particular, distributions involving excited states are extracted. The exponential decay of the charge and matter distributions can be described by mesons of mass 0.9+-0.1 and 1.5+-0.1 GeV respectively - values that are consistent with those of vector and scalar qqbar-states calculated directly with the same lattice parameters.
Z. Fodor🇭🇺
Recent lattice results on QCD at finite temperatures and densities are reviewed. Two new and independent techniques give compatible results for physical quantities. The phase line separating the hadronic and quark-gluon plasma phases, the critical endpoint and the equation of state are discussed.
L. Giusti🇫🇷 · S. Petrarca🇮🇹 · B. Taglienti🇮🇹 · N. Tantalo🇮🇹
The gauge dependence of some fermion bilinear RI/MOM renormalization constants is studied by comparing data which have been gauge-fixed in two different realizations of the Landau gauge and in a generic covariant gauge. The very good agreement between the various sets of results and the theory indicates that the numerical uncertainty induced by the lattice gauge-fixing procedure is below the statistical errors of our data sample which is of the order of (1-1.5)%.
Thomas Neuhaus · Arttu Rajantie🇬🇧 · Kari Rummukainen🇸🇪
It has been conjectured that the phase transition in the Ginzburg-Landau theory is dual to the XY model transition. We study numerically a particular limit of the GL theory where this duality becomes exact, clarifying some of the problems encountered in standard GL theory simulations. This may also explain the failure of the superconductor experiments to observe the XY model scaling.
N. Cundy🇬🇧 · M. Teper🇬🇧 · U. Wenger🇬🇧
We address the question of whether the low modes of the Dirac operator are caused by topological objects such as instantons in SU(N) gauge theories. We study the pseudo-scalar density of these modes, finding the size distributions of the instantons, and comparing it with the underlying gauge field. We find that, although the near-zero modes of the Dirac operator depend on topology for all N, their small instanton content decreases as N increases.
We compare the physical potential of an external quark-antiquark pair in the representation of SU(N), to the color-Coulomb potential which is the instantaneous part of the 44-component of the gluon propagator in Coulomb gauge, + (non-instantaneous). We show that if is confining, , then the inequality holds asymptotically at large , where is the Casimir in the representation . This implies that is also confining.
Henrique Boschi-Filho🇧🇷 · Nelson R. F. Braga🇧🇷
Recently Polchinski and Strassler reproduced the high energy QCD scaling at fixed angles from a gauge string duality inspired in AdS/CFT correspondence. In their approach a confining gauge theory is taken as approximately dual to an AdS space with an IR cut off. Considering such an approximation (AdS slice) we found a one to one holographic mapping between bulk and boundary scalar fields. Associating the bulk fields with dilatons and the boundary fields with glueballs of the confining gauge theory we also found the same high energy QCD scaling. Here, using this holographic mapping we give a simple estimate for the mass ratios of the glueballs assuming the AdS slice approximation to be valid at low energies. We also compare these results to those coming from supergravity and lattice QCD.
* 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.