HEP Lattice·hep-lat

Fri·Sep 23, 2005Friday·September 23, 2005

19 papers—19 primary·0 cross-listed·reconstructed*

01*
Exploring the spectrum of QCD using a space-time lattice
Colin Morningstar🇺🇸
Some past and ongoing explorations of the spectrum of QCD using Monte Carlo simulations on a space-time lattice are described. Glueball masses in the pure-gauge theory are reviewed, and the energies of gluonic excitations in the presence of a static quark-antiquark pair are discussed. Current efforts to compute the baryon spectrum using extended three-quark operators are also presented, emphasizing the need to use irreducible representations of the cubic point group to identify spin quantum numbers in the continuum limit.
hep-latInt.J.Mod.Phys.A(2006)·3 citations
02*
Restoring chiral symmetry to O(a^2) for dynamical Wilson fermions
Roland Hoffmann🇺🇸 · Michele Della Morte🇩🇪 · Francesco Knechtli🇩🇪 · Rainer Sommer🇩🇪 · Ulli Wolff🇩🇪
We present results for the non-perturbative determination of the improvement and renormalization factors of the isovector axial current for lattice QCD with two flavors of dynamical Wilson quarks. The improvement and normalization conditions are formulated in terms of matrix elements of the PCAC relation in the Schroedinger functional setup and results are given in the form of interpolating formulae for bare gauge couplings beta=6/g_0^2>5.2.
hep-latPoS(2006)·1 citation
03*
The pion mass in finite volume to two loops
Christoph Haefeli🇨🇭
We evaluate the pion mass in finite volume to two loops within Chiral Perturbation Theory. The results are compared with a recently proposed extension of the asymptotic formula of Luscher. We find that contributions, which were neglected in the latter, are numerically very small at the two-loop level.
hep-latPoS(2006)·2 citations
04*
Low-lying spectrum for lattice Dirac operators with twisted mass
Christof Gattringer🇦🇹 · Stefan Solbrig🇩🇪
We analyze the low-lying spectrum and eigenmodes of lattice Dirac operators with a twisted mass term. The twist term expels the eigenvalues from a strip in the complex plane and all eigenmodes obtain a non-vanishing matrix element with gamma-5. For a twisted Ginsparg-Wilson operator the spectrum is located on two arcs in the complex plane. Modes due to non-trivial topological charge of the underlying gauge field have their eigenvalues at the edges of these arcs and obey a remnant index theorem. For configurations in the confined phase we find that the twist mainly affects the zero modes, while the bulk of the spectrum is essentially unchanged.
hep-latPoS(2006)·1 citation
05*
Speeding up the HMC algorithm: Some new results
Martin Hasenbusch🇮🇹
We give some new performance results for the Hybrid Monte Carlo (HMC) simulation of dynamical clover-improved Wilson fermions using an improved pseudo-fermion action. The generalisation of even-odd preconditioning for the standard Wilson fermion matrix to the clover-improved case is not unique. In the literature the so called symmetric and asymmetric versions are discussed. Most of the previous simulations of dynamical clover-improved Wilson fermions were done with the asymmetric version. Only recently, the JLQCD collaboration has pointed out that the symmetric version leads to a better performance of the HMC algorithm. Here, we show that also in combination with an improved pseudo-fermion action, the symmetric version of even-odd preconditioning leads to a better performance. For our lightest quark mass, which corresponds to $m_{P S} / m_{V} \approx 0.44$ , we see a gain in performance by a factor of about 1.3.
hep-latPoS(2006)·4 citations
06*
Kosterlitz-Thouless transition on the worldsheet of the QCD string
Harvey B. Meyer🇩🇪
We investigate the properties of the QCD string in the Euclidean SU(N) pure gauge theory when the space-time dimensions transverse to it are periodic. We propose a generalisation of the Luscher-Weisz effective string action for the flux-tube energy levels at finite L_perp. As the size of one transverse dimension is varied, we predict a Kosterlitz-Thouless transition of the worldsheet field theory driven by vortices, after which the periodic component of the worldsheet displacement vector develops a mass gap and the effective central charge drops by one unit. The universal properties of the transition are emphasized.
hep-latPoS(2006)·2 citations
07*
The deconfining phase transition for SU(N) theories in 2+1 dimensions
Jack Liddle🇬🇧 · Mike Teper🇬🇧
The critical temperatures for the 2+1 dimensional $S U (N_{c})$ gauge theories are calculated, for $N_{c} = 4, 5, 6$ . The transition is shown to be first order for $N_{c} \geq 5$ . The critical temperature and latent heat are extrapolated to $N_{c} = \infty$ .
hep-latPoS(2006)·23 citations
08*
Effects of partial quenching and staggered fermions on the scalar correlator
S. Prelovsek🇸🇮
We determine the mass of the lightest quark-antiquark scalar meson with I=1 using the simulation with two dynamical Domain Wall Fermions. The conventional exponential fit of the scalar correlator is justified in this case giving the mass 1.58 +/- 0.34 GeV. In general the scalar correlator receives also the bubble contribution, which is the intermediate state with two pseudoscalar mesons. This contribution is sizable at light quark masses and has to be incorporated in the fit of the scalar correlator in order to extract the scalar meson mass. We provide predictions for the bubble contribution in Partially Quenched ChPT, Staggered ChPT and ChPT for Mixed quark actions. We find that the bubble contribution is significantly affected by the unphysical approximations that are employed in simulations. It can render the negative sign and unphysical effective mass 2*Mpi in the scalar correlator with I=1.
hep-latPoS(2006)·8 citations
09*
A strategy for the computation of m_b including 1/m terms
Michele Della Morte🇩🇪 · Nicolas Garron🇩🇪 · Rainer Sommer🇩🇪 · Mauro Papinutto🇩🇪
We consider HQET including the first order correction in 1/m. A strategy for the computation of the b-quark mass is discussed. Only two quantities Phi_1/2 have to be considered in order to match QCD and HQET, since the spin-dependent interaction is easily eliminated due to the spin symmetry of the static theory. Quite simple formulae relate the renormalization group invariant b-quark mass (M_b) to the B-meson mass. All entries in these formulae are non-perturbatively defined and can be computed in the continuum limit of the lattice regularized theory. For the numerically most critical part, we illustrate the cancellation of power divergences by a numerical example. Numerical results for the 1/m correction to M_b, are presented in a companion talk.
hep-latPoS(2006)·1 citation
10*
Screening of sources in higher representations of SU(N) gauge theories at zero and finite temperature
F. Gliozzi🇮🇹
Completion of the Svetitsky-Yaffe conjecture in some (2+1) dimensional SU(N) gauge theories allows mapping Polyakov loops in higher representations of the gauge group into suitable conformal operators of the corresponding 2D CFT. As a consequence, the critical exponents of the correlators of these Polyakov loops are determined. The functional form of these correlators suggests a general Ansatz to describe the large-distance screening of higher-representation sources at zero temperature in any space-time dimension. A generalised Wilson loop in which along part of its trajectory a source is converted in a gauge invariant way into higher representations with same N-ality could be used to estimate the decay scale of the unstable strings
hep-latPoS(2006)·3 citations
11*
Excited meson spectroscopy with chirally improved fermions
T. Burch🇩🇪 · C. Gattringer🇦🇹 · L. Glozman🇦🇹 · C. Hagen🇩🇪 · D. Hierl🇩🇪 · C. B. Lang🇦🇹 · A. Schäfer🇩🇪
We present excited meson masses from quenched calculations using chirally improved (CI) quarks at pion masses down to 350 MeV. The salient features of our analysis are the use of a matrix of correlators from various source and sink operators and a basis which includes quark sources with different spatial widths, thereby improving overlap with states exhibiting radial excitations.
hep-latPoS(2006)·10 citations
12*
Laplacian modes for calorons and as a filter
Falk Bruckmann🇳🇱 · Ernst-Michael Ilgenfritz🇩🇪
We compute low-lying eigenmodes of the gauge covariant Laplace operator on the lattice at finite temperature. For classical configurations we show how the lowest mode localizes the monopole constituents inside calorons and that it hops upon changing the boundary conditions. The latter effect we observe for thermalized backgrounds, too, analogously to what is known for fermion zero modes. We propose a new filter for equilibrium configurations which provides link variables as a truncated sum involving the Laplacian modes. This method not only reproduces classical structures, but also preserves the confining potential, even when only a few modes are used.
hep-latPoS(2006)·5 citations
13*
An Abelian two-Higgs model and high temperature superconductivity
M.N. Chernodub🇷🇺 · Arwed Schiller🇩🇪 · E.-M. Ilgenfritz🇩🇪
We study a three dimensional Abelian Higgs model containing singly- and doubly-charged scalar fields coupled to a compact Abelian gauge field in the London limit. The model attracts interest because of its relevance to high-Tc superconductors with charge 1 holon and charge 2 spinon-pair fields. It contains two types of vortices carrying magnetic flux and one type of instanton-like monopoles. Using thermodynamic and topological observables we present the phase diagram in the parameter space of the gauge and holon and spinon-pair couplings. The Fermi liquid, the spin gap, the superconductor and the strange metallic phases have been identified in a wide region of parameters. The model may serve as a toy system modelling non-perturbative properties of the Yang-Mills theory.
hep-latcond-mat.str-elhep-thPoS(2006)·1 citation
14*
Towards SU(2) invariant formulation of the monopole confinement mechanism
Katsuya Ishiguro🇯🇵 · Yoshihiro Mori🇯🇵 · Yoshifumi Nakamura🇯🇵 · Toru Sekido🇯🇵 · Tsuneo Suzuki🇯🇵 · M.N. Chernodub🇷🇺 · M.I. Polikarpov🇷🇺 · V.I. Zakharov🇩🇪
The type of the vacuum is studied numerically in the maximally Abelian (MA) gauge and in the Landau (LA) gauge of SU(2) gluodynamics. The type of the vacuum is determined by a ratio between the dual coherence and the dual penetration lengths. The dual penetration length is determined from correlations between Wilson loops and electric fields in both gauges. The dual coherence length is found from correlations between Wilson loops and dimension-2 operators both in the MA and the LA gauges. This determination of the coherence length is supported by theoretical and numerical observation that the dimension-2 gluon operators in the studied gauges have a strong correlation with the monopole current determined in the MA gauge. We find numerically that the dual penetration lengths and the dual coherence lengths in the LA and the MA gauges are almost the same. Therefore we conclude, that in both gauges the type of the vacuum in the confinement phase is near to the border between the type 1 and the type 2 dual superconductors.
hep-lathep-phhep-thPoS(2006)·2 citations
15*
Studying the infrared region in Landau gauge QCD
A. Sternbeck🇩🇪 · E.-M. Ilgenfritz🇩🇪 · M. Mueller-Preussker🇩🇪 · A. Schiller🇩🇪
We report on the progress we made in studying the infrared behavior of the ghost and gluon dressing functions in Landau gauge. Related to this we also investigate a running coupling given in terms of those functions and compare our results to those coming from the Dyson-Schwinger approach. We present first numerical results for the SU(3) ghost-ghost-gluon vertex renormalization constant. In addition the spectrum of low-lying eigenvalues and eigenfunctions of the Faddeev-Popov operator is determined. The saturation of the ghost propagator in terms of those eigenvalues and eigenmodes is discussed at lower momenta.
hep-latPoS(2006)·15 citations
16*
Non-perturbatively Renormalized Light Quark Masses with Two Dynamical Fermions
D. Becirevic🇫🇷 · B. Blossier🇫🇷 · Ph. Boucaud🇫🇷 · V. Gimenez🇪🇸 · V. Lubicz🇮🇹 · F. Mescia🇮🇹 · S. Simula🇮🇹 · C. Tarantino🇮🇹
We present the results of a partially quenched lattice QCD calculation of light quark masses with $N_{f} = 2$ degenerate dynamical flavors. Numerical simulations are carried out using the plaquette gauge action and the Wilson quark action at $β = 5.8$ ( $a^{- 1} ≃ 3.2 \gev$ ). The spatial extension of the $2 4^{3} \times 48$ lattice is about 1.5 fm. Configurations have been generated at four values of the sea quark masses, for which the ratio of pseudoscalar over vector meson masses is in the range $M_{P} / M_{V} ≃ 0.60 \div 0.75$ . An important feature of the present study is the use of non-perturbative renormalization, performed with the $\ri$ method. The effects of dynamical sea quarks in the determination of light quark masses have been investigated by performing a quenched calculation on a similar lattice. Our results for the average up-down and strange quark masses are $m_{u d}^{M S} (2 \gev) = 4.3 (4) (_{- 0.4}^{+ 1.1}) \mev$ and $m_{s}^{M S} (2 \gev) = 101 (8) (_{- 9}^{+ 25}) \mev$ . These values are larger than those obtained by evaluating the quark mass renormalization constants with one-loop (boosted) perturbation theory. Our results for the light quark masses are compatible with those obtained in the quenched simulation. No significant sea quark effects are seen, at the values of sea quark masses used in the present study.
hep-latPoS(2006)·8 citations
17*
Phase transitions and non-analyticities in large N gauge theories
Francis Bursa🇬🇧 · Michael Teper🇬🇧 · Helvio Vairinhos🇬🇧
We investigate numerically various phase transitions and non-analyticities at large N using both twisted Eguchi-Kawai space-time reduction and the standard Wilson theory.
hep-latPoS(2006)·4 citations
18*
Partially Twisted Boundary Conditions in Lattice Simulations
Jonathan Flynn🇬🇧 · Andreas Juttner🇬🇧 · Christopher Sachrajda🇬🇧 · Giovanni Villadoro🇮🇹
We use chiral perturbation theory to investigate twisted and partially twisted boundary conditions which allow access to momenta other than integer multiples of 2pi/L on a lattice with spatial volume L^3. For K -> pi pi decays we show that the breaking of isospin symmetry by the twisted boundary conditions implies that the amplitudes cannot be determined in general. We find numerical evidence for the result that the finite volume effects of the boundary conditions are exponentially suppressed for quantities without final state interactions (meson masses and meson-to-vacuum matrix elements) in a simulation with partial twisting on a sea of N_f=2 non-perturbatively improved Wilson quarks.
hep-latPoS(2006)·8 citations
19*
Magnetic field production after inflation
Andres Diaz-Gil🇪🇸 · J. Garcia-Bellido🇪🇸 · M. Garcia Perez🇪🇸 · A. Gonzalez-Arroyo🇪🇸
We study the electromagnetic field production during preheating after hybrid inflation in a model with the field content of the Standard Model, coupled to a singlet inflaton. We find that very soon after symmetry breaking our system enters a regime of kinetic turbulence, characterized by a self-similar behaviour of the energy spectra and a power-like dependence on time of the inflaton and Higgs field variances.
hep-lathep-phPoS(2006)·21 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.