PaperPanorama

HEP Lattice·hep-lat

Wed·Sep 15, 2004

28 papers—27 primary·1 cross-listed·reconstructed*

All28Primary27Cross-lists1
  1. 01*

    SU(N) chiral gauge theories on the lattice: a quick overview

    Maarten Golterman (SFSU)🇺🇸 · Yigal Shamir (Tel Aviv)🇮🇱

    We describe how an SU(N) chiral gauge theory can be put on the lattice using non-perturbative gauge fixing. In particular, we explain how the Gribov problem is dealt with. Our construction is local, avoids doublers, and weak-coupling perturbation theory applies at the critical point which defines the continuum limit of our lattice chiral gauge theory.

    hep-lathep-phhep-thNucl.Phys.B Proc.Suppl.(2005)·2 citations
  3. 03*

    The scaling equation of state of the three-dimensional O(N) universality class: N >= 4

    Agostino Butti🇮🇹 · Francesco Parisen Toldin🇮🇹 · Andrea Pelissetto🇮🇹 · Ettore Vicari🇮🇹

    We determine the critical equation of state of the three-dimensional O(N) universality class, for N=4, 5, 6, 32, 64. The N=4 is relevant for the chiral phase transition in QCD with two flavors, the N=5 model is relevant for the SO(5) theory of high-T_c superconductivity, while the N=6 model is relevant for the chiral phase transition in two-color QCD with two flavors. We first consider the small-field expansion of the effective potential (Helmholtz free energy). Then, we apply a systematic approximation scheme based on polynomial parametric representations that are valid in the whole critical regime, satisfy the correct analytic properties (Griffiths' analyticity), take into account the Goldstone singularities at the coexistence curve, and match the small-field expansion of the effective potential. From the approximate representations of the equation of state, we obtain estimates of universal amplitude ratios. We also compare our approximate solutions with those obtained in the large-N expansion, up to order 1/N, finding good agreement for N \gtrsim 32.

    hep-latNucl.Phys.B Proc.Suppl.(2005)·1 citation
  5. 05*

    Improving meson two-point functions by low-mode averaging

    T. DeGrand🇺🇸 · S. Schaefer🇺🇸

    Some meson correlation functions have a large contribution from the low lying eigenmodes of the Dirac operator. The contribution of these eigenmodes can be averaged over all positions of the source. This can improve the signal in these channels significantly. We test the method for meson two-point functions.

    hep-latNucl.Phys.B Proc.Suppl.(2005)·23 citations
  6. 06*

    One-loop determination of mass dependent improvement coefficients for the heavy-light vector and axial-vector currents with relativistic heavy and domain-wall light quarks

    Norikazu Yamada🇺🇸 · Sinya Aoki🇯🇵 · Yoshinobu Kuramashi🇯🇵

    We present the one-loop results of the mass dependent improvement coefficients for the heavy-light vector and axial-vector currents consisting of the relativistic heavy and the domain-wall light quarks. The calculations are performed with the plaquette, Iwasaki and DBW2 gauge actions. The heavy quark mass and domain-wall height dependence is investigated. We point out that the exact chiral symmetry held by the lattice light quark action leads to an exact relation between the improvement coefficients for the vector and axial-vector currents without regard to the lattice heavy quark action.

    hep-latNucl.Phys.B Proc.Suppl.(2005)·0 citations
  7. 07*

    Signal at subleading order in lattice HQET

    S. Dürr🇩🇪 · A. Jüttner🇩🇪 · J. Rolf🇩🇪 · R. Sommer🇩🇪

    We discuss the correlators in lattice HQET that are needed to go beyond the static theory. Based on our implementation in the Schrödinger functional we focus on their signal-to-noise ratios and check that a reasonable statistical precision can be reached in quantities like and .

    hep-latNucl.Phys.B Proc.Suppl.(2005)·6 citations
  8. 08*

    First Simulation Results for the Photon in a Non-Commutative Space

    W. Bietenholz🇩🇪 · F. Hofheinz🇩🇪 · J. Nishimura🇯🇵 · Y. Susaki🇯🇵 · J. Volkholz🇩🇪

    We present preliminary simulation results for QED in a non-commutative 4d space-time, which is discretized to a fuzzy lattice. Its numerical treatment becomes feasible after its mapping onto a dimensionally reduced twisted Eguchi-Kawai matrix model. In this formulation we investigate the Wilson loops and in particular the Creutz ratios. This is an ongoing project which aims at non-perturbative predictions for the photon, which can be confronted with phenomenology in order to verify the possible existence of non-commutativity in nature.

    hep-lathep-thNucl.Phys.B Proc.Suppl.(2005)·12 citations
  9. 09*

    Exploring Lattice Methods for Cold Fermionic Atoms

    Matthew Wingate🇺🇸

    There has been a surge of experimental effort recently in cooling trapped fermionic atoms to quantum degeneracy. By varying an external magnetic field, interactions between atoms can be made arbitrarily strong. When the S wave scattering length becomes comparable to and larger than the interparticle spacing, standard mean field analysis breaks down. In this case the system exhibits a type of universality, and J-W. Chen and D. B. Kaplan recently showed how this system can be studied from first principles using lattice field theory. This poster presents the first results of exploratory simulations. The existence of a continuum limit is checked and the pairing condensate is studied as a function of the external source strength over a range of temperatures. Preliminary results show simulations can locate the critical temperature.

    hep-latcond-mat.softcond-mat.stat-mechnucl-thNucl.Phys.B Proc.Suppl.(2005)·7 citations
  11. 11*

    Index Theorem and Random Matrix Theory for Improved Staggered Quarks

    E. Follana🇬🇧

    We study various improved staggered quark Dirac operators on quenched gluon backgrounds in lattice QCD generated using a Symanzik-improved gluon action. We find a clear separation of the spectrum of eigenvalues into would-be zero modes and others. The number of would-be zero modes depends on the topological charge as expected from the Index Theorem, and their chirality expectation value is large. The remaining modes have low chirality and show clear signs of clustering into quartets and approaching the random matrix theory predictions for all topological charge sectors. We conclude that improvement of the fermionic and gauge actions moves the staggered quarks closer to the continuum limit where they respond correctly to QCD topology.

    hep-latNucl.Phys.B Proc.Suppl.(2005)·9 citations
  12. 12*

    I=2 Pion Scattering Length from Two-Pion Wave Function

    CP-PACS Collaboration : S. Aoki🇯🇵 · M. Fukugita🇯🇵 · K-I. Ishikawa🇯🇵 · N. Ishizuka🇯🇵 · Y. Iwasaki🇯🇵 · K. Kanaya🇯🇵 · T. Kaneko🇯🇵 · Y. Kuramashi🇯🇵 · M. Okawa🇯🇵 · A. Ukawa🇯🇵 · T. Yamazaki🇺🇸 · T. Yoshié🇯🇵

    We present a report on a calculation of scattering length for I=2 -wave two-pion system from two-pion wave function. Calculations are made with an RG-improved action for gluons and improved Wilson action for quarks at on , and lattices. We investigate the validity of necessary condition for application of Lüscher's formula through the wave function. We find that the condition is satisfied for lattice volumes for the quark mass range . We also find that the scattering length can be extracted with a smaller statistical error from the wave function than with a time correlation function used in previous studies.

    hep-latNucl.Phys.B Proc.Suppl.(2005)·12 citations
  15. 15*

    Chiral perturbation theory for twisted mass QCD

    Gernot Münster🇩🇪 · Christian Schmidt (University of Muenster)🇩🇪 · Enno E. Scholz (DESY Hamburg)🇩🇪

    Quantum Chromodynamics on a lattice with Wilson fermions and a chirally twisted mass term for two degenerate quark flavours is considered in the framework of chiral perturbation theory. The pion masses and decay constants are calculated in next-to-leading order including terms linear in the lattice spacing a. We treat both unquenched and partially quenched QCD. We also discuss the phase structure of twisted mass lattice QCD.

    hep-latNucl.Phys.B Proc.Suppl.(2005)·14 citations
  16. 16*

    Lattice artefacts in SU(3) lattice gauge theory with a mixed fundamental and adjoint plaquette action

    Martin Hasenbusch🇬🇧 · Silvia Necco (CPT)🇫🇷

    We investigated SU(3) lattice gauge theory with a fundamental and adjoint plaquette term in the action. The purpose is to test whether the choice of a negative adjoint coupling can reduce lattice artefacts and improve the scaling b ehaviour. To this end, we have studied the finite temperature phase transition, the static potential and the mass of the 0^{++} glueball. We found that indeed the lattice artefacts in e.g. m_{0^{++}}/T_c can be reduced considerably compared with the pure Wilson (fundamental) gauge action at the same lattice spacing.

    hep-latNucl.Phys.B Proc.Suppl.(2005)·3 citations
  17. 17*

    Exact supersymmetry on the lattice: the Wess-Zumino model

    Marisa Bonini🇮🇹 · Alessandra Feo🇮🇹

    It is shown that the lattice Wess-Zumino model written in terms of Ginsparg-Wilson fermions is invariant under a generalized supersymmetry transformation which is determined by an iterative procedure in the coupling constant. This transformation is non-linear in the scalar fields and depends on the superpotential parameters. The implications of this lattice invariance are discussed.

    hep-latNucl.Phys.B Proc.Suppl.(2005)·4 citations
  18. 18*

    Improving Algorithms to Compute All Elements of the Lattice Quark Propagator

    Alan O Cais🇮🇪 · K.Jimmy Juge🇮🇪 · Mike J. Peardon🇮🇪 · Sinead M. Ryan🇮🇪 · Jon-Ivar Skullerud (TrinLat Collaboration)🇮🇪

    We present a new exact algorithm for estimating all elements of the quark propagator. The advantage of the method is that the exact all-to-all propagator is reproduced in a large but finite number of inversions. The efficacy of the algorithm is tested in Monte Carlo simulations of Wilson quarks in quenched QCD. Applications that are difficult to probe with point propagators are discussed.

    hep-latNucl.Phys.B Proc.Suppl.(2005)·25 citations
  19. 19*

    Dynamical overlap fermions, results with HMC algorithm

    Z. Fodor🇩🇪 · S.D. Katz🇩🇪 · K.K. Szabo🇩🇪

    We present results of a hybrid Monte-Carlo algorithm for dynamical, , four-dimensional QCD with overlap fermions. The fermionic force requires careful treatment, when changing topological sectors. The pion mass dependence of the topological susceptibility is studied on and lattices. The results are transformed into physical units.

    hep-latNucl.Phys.B Proc.Suppl.(2005)·25 citations
  20. 20*

    APENet: LQCD clusters a la APE

    R. Ammendola (1)🇮🇹 · M. Guagnelli (1)🇮🇹 · G. Mazza (1)🇮🇹 · F. Palombi (2)🇮🇹 · R. Petronzio (1 and 3)🇮🇹 · D. Rossetti (4)🇮🇹 · A. Salamon (1)🇮🇹 · P. Vicini (4) ((1) INFN RM2, (2) E. Fermi Research Center, (3) Tor Vergata University, (4) INFN RM1)🇮🇹

    Developed by the APE group, APENet is a new high speed, low latency, 3-dimensional interconnect architecture optimized for PC clusters running LQCD-like numerical applications. The hardware implementation is based on a single PCI-X 133MHz network interface card hosting six indipendent bi-directional channels with a peak bandwidth of 676 MB/s each direction. We discuss preliminary benchmark results showing exciting performances similar or better than those found in high-end commercial network systems.

    hep-latNucl.Phys.B Proc.Suppl.(2005)·6 citations
  21. 21*

    QCD at small baryon number

    Slavo Kratochvila (Zurich, ETH)🇨🇭 · Philippe de Forcrand (Zurich, ETH & CERN)🇨🇭

    We consider the difficulties of finite density QCD from the canonical formalism. We present results for small baryon numbers, where the sign problem can be controlled, in particular by supplementing the mu=0 sampling with imaginary mu ensembles. We initiate the thermodynamic study of few-nucleon systems, starting with the measurement of the free energy of a few baryons in the confined and deconfined phase. We present a simple model for the phase transition, whose results are in good agreement with the literature, but extend to lower temperatures.

    hep-latNucl.Phys.B Proc.Suppl.(2005)·31 citations
  22. 22*

    Testing a Topology Conserving Gauge Action in QCD

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

    We study lattice QCD with a gauge action, which suppresses small plaquette values. Thus the MC history is confined to a single topological sector over a significant time, while other observables are decorrelated. This enables the cumulation of statistics with a specific topological charge, which is needed for simulations of QCD in the -regime. The same action may also be useful for simulations with dynamical quarks. The update is performed with a local HMC algorithm.

    hep-latNucl.Phys.B Proc.Suppl.(2005)·12 citations
  23. 23*

    Study of the 2-d CP(N-1) models at \theta=0 and \pi

    B.B. Beard🇺🇸 · M. Pepe🇨🇭 · S. Riederer🇨🇭 · U.J. Wiese🇨🇭

    We present numerical results for 2-d CP(N-1) models at \theta=0 and \pi obtained in the D-theory formulation. In this formulation we construct an efficient cluster algorithm and we show numerical evidence for a first order transition for CP(N-1\geq 2) models at \theta = \pi. By a finite size scaling analysis, we also discuss the equivalence in the continuum limit of the D-theory formulation of the 2-d CP(N-1) models and the usual lattice definition.

    hep-latNucl.Phys.B Proc.Suppl.(2005)·1 citation
  24. 24*

    Sea quark effects in B_K from N_f=2 clover-improved Wilson fermions

    J. M. Flynn🇬🇧 · F. Mescia🇮🇹 · A. S. B. Tariq (for the UKQCD Collaboration)🇬🇧

    We report calculations of B_K using two flavours of dynamical clover-improved Wilson lattice fermions and look for dependence on the dynamical quark mass at fixed lattice spacing. We see some evidence for dynamical quark effects. In particular B_K decreases as the sea quark masses are reduced towards the up/down quark mass. Our meson masses are quite heavy and a firm prediction of B_K is a task for future simulations.

    hep-latNucl.Phys.B Proc.Suppl.(2005)·2 citations
  25. 25*

    Heavy meson chiral perturbation theory in finite volume

    C.-J. David Lin (University of Washington, Seattle)🇺🇸

    We present the first step towards the estimation of finite volume effects in heavy-light meson systems using heavy meson chiral perturbation theory. We demonstrate that these effects can be amplified in both light-quark and heavy-quark mass extrapolations (interpolations) in lattice calculations. As an explicit example, we perform a one-loop calculation for the neutral B meson mixing system and show that finite volume effects, which can be comparable with currently quoted errors, are not negligible in both quenched and partially quenched QCD.

    hep-lathep-phNucl.Phys.B Proc.Suppl.(2005)·1 citation
  26. 26*

    The lattice QCD simulation of the quark-gluon mixed condensate g<\bar{q} \sigma G q> at finite temperature and the phase transition of QCD

    Takumi Doi (1)🇺🇸 · Noriyoshi Ishii (2)🇯🇵 · Makoto Oka (2)🇯🇵 · Hideo Suganuma (2) ((1) RIKEN BNL, (2) Tokyo Inst. Tech)🇯🇵

    The thermal effects on the quark-gluon mixed condensate g<\bar{q} \sigma G q>, which is another chiral order parameter, are studied using the SU(3)c lattice QCD with the Kogut-Susskind fermion at the quenched level. We perform the accurate measurement of the mixed condensate as well as the quark condensate for 0MeV<=T<=500MeV. We observe the sharp decrease of both the condensates around T_c \simeq 280MeV, while the thermal effects below T_c are found to be weak. We also find that the ratio m_0^2 = g<\bar{q} \sigma G q>/<\bar{q}q> is almost independent of the temperature even in the very vicinity of T_c, which indicates that the two condensates have nontrivial similarity in the chiral behaviors. We also present the correlation between the condensates and the Polyakov loop to understand the vacuum structure of QCD.

    hep-lat2 citations
  27. 27*

    The two-grid algorithm confronts a shifted unitary orthogonal method

    Artan Borici🇦🇱

    In this paper I describe a new optimal Krylov subspace solver for shifted unitary matrices called the Shifted Unitary Orthogonal Method (SUOM). This algorithm is used as a benchmark against any improvement like the two-grid algorithm. I use the latter to show that the overlap operator can be inverted by successive inversions of the truncated overlap operator. This strategy results in large gains compared to SUOM.

    hep-latNucl.Phys.B Proc.Suppl.(2005)·3 citations
  28. 28*

    Correction-to-scaling exponents for two-dimensional self-avoiding walks

    Sergio Caracciolo🇮🇹 · Anthony J. Guttmann🇦🇺 · Iwan Jensen🇦🇺 · Andrea Pelissetto🇮🇹 · Andrew N. Rogers🇦🇺 · Alan D. Sokal🇺🇸

    We study the correction-to-scaling exponents for the two-dimensional self-avoiding walk, using a combination of series-extrapolation and Monte Carlo methods. We enumerate all self-avoiding walks up to 59 steps on the square lattice, and up to 40 steps on the triangular lattice, measuring the mean-square end-to-end distance, the mean-square radius of gyration and the mean-square distance of a monomer from the endpoints. The complete endpoint distribution is also calculated for self-avoiding walks up to 32 steps (square) and up to 22 steps (triangular). We also generate self-avoiding walks on the square lattice by Monte Carlo, using the pivot algorithm, obtaining the mean-square radii to ~0.01% accuracy up to N = 4000. We give compelling evidence that the first non-analytic correction term for two-dimensional self-avoiding walks is Delta_1 = 3/2. We compute several moments of the endpoint distribution function, finding good agreement with the field-theoretic predictions. Finally, we study a particular invariant ratio that can be shown, by conformal-field-theory arguments, to vanish asymptotically, and we find the cancellation of the leading analytic correction.

    ↳ cond-mat.stat-mechhep-latJ.Statist.Phys.(2005)·10 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.