Wed·Oct 10, 2007Wednesday·October 10, 2007

1. 01*

   Vacuum Expectation Values of Twisted Mass Fermion Operators

   Abdou Abdel-Rehim🇺🇸 · Randy Lewis🇨🇦 · Walter Wilcox🇺🇸

   Using noise methods on a quenched $20^3\times 32$ lattice at $\beta =6.0$, we have investigated vacuum expectation values and relative linear correlations among the various Wilson and twisted mass scalar and pseudoscalar disconnected loop operators. We show results near the maximal twist lines in $\kappa$, $\mu$ parameter space, either defined as the absence of parity mixing or the vanishing of the PCAC quark mass.

   hep-latPoS(2007)·0 citations
2. 02*

   Toward a precise determination of Tc with 2+1 flavors of quarks

   Carleton DeTar (U. Utah)🇺🇸 · Rajan Gupta (LANL) (for the HotQCD Collaboration)🇺🇸

   We present a status report on a new high statistics study of the high temperature transition in full QCD at zero chemical potential. Our simulations use both improved asqtad and p4 staggered quarks on lattices with a temporal extent N_t = 8 and light quark masses approximately one tenth the strange quark mass. In this report we describe the setup of our calculations and present a preliminary analysis of a variety of sources of systematic error and ambiguity in the determination of the crossover temperature. We propose to present our final analysis with double the current statistics. These calculations were carried out on the IBM BlueGene/L supercomputer at Lawrence Livermore National Laboratory.

   hep-latPoS(2007)·27 citations
3. 03*

   Sharing lattices throughout the world: an ILDG status report

   Carleton DeTar (U. Utah)🇺🇸

   The international lattice data grid, a system for sharing gauge configuration files throughout the world, is operational for the most part. I give a status report, give some pointers on accessing lattice files, and highlight some of the available gauge configurations.

   hep-latPoS(2007)·14 citations
4. 04*

   Excited State Spectroscopy in the Lattice Gross-Neveu Model

   Julia Danzer🇦🇹 · Christof Gattringer🇦🇹

   We present preliminary results of an excited state spectroscopy calculation in the 2-d lattice Gross-Neveu model. We address the construction of suitable interpolators for the variational method and their overlap with excitations. We comment on the role of the eigenvectors as a tool for matching scattering states on lattices with different volumes.

   hep-latPoS(2007)·8 citations
5. 05*

   An update in monopole condensation in two-flavour Adjoint QCD

   G. Lacagnina🇮🇹 · G. Cossu🇮🇹 · M. D'Elia🇮🇹 · A. Di Giacomo🇮🇹 · C. Pica🇺🇸

   QCD with fermions in the adjoint representation (aQCD) is a model for which a deconfinement and a chiral phase transition take place at different temperatures. In this work, we present a study of the deconfinement transition in the dual superconductor picture based on the evaluation of an operator which carries magnetic charge. The expectation value of this operator signals monopole condensation and is an order parameter for deconfinement as in the case of fermions in the fundamental representation. We find a sharp first order deconfinement transition. We also study the effects of the chiral transition on the monopole order parameter and find them negligible.

   hep-latPoS(2007)·0 citations
6. 06*

   Layered Phase Investigations

   S. Nicolis🇫🇷

   The extra dimensional defects that are introduced to generate the lattice chiral zero modes are not simply a computational trick, but have interesting physical consequences. After reviewing what is known about the layered phase they can generate, I argue how it is possible to simulate Yang-Mills theories with reduced systematic errors and speculate on how it might be possible to study the fluctuations of the layers' topological charge.

   hep-latPoS(2007)·5 citations
7. 07*

   Meson mass spectrum at finite temperature and density in the strong coupling limit of lattice QCD for color SU(3)

   Noboru Kawamoto🇯🇵 · Kohtaroh Miura🇯🇵 · Akira Ohnishi🇯🇵

   We investigate the meson mass spectrum in the strong coupling limit of lattice QCD with one species of staggered fermion for the SU(N_c) color gauge group, including N_c=3. We analytically derive meson masses as functions of temperature and chemical potential via chiral condensates. We show that meson masses quickly decrease to zero when the chemical potential or the temperature approaches to the critical value.

   hep-latnucl-thPoS(2007)·10 citations
8. 08*

   Pseudoscalar Flavor-Singlet Physics with Staggered Fermions

   Eric B. Gregory🇬🇧 · Alan Irving🇬🇧 · Chris M. Richards🇬🇧 · Craig McNeile🇬🇧 · Alistair Hart🇬🇧

   Accurately calculating the mass of flavor-singlet meson states from numerical lattice simulations is an important milestone for lattice QCD. Careful measurement of the full pseudoscalar flavor-singlet propagator is also a crucial step in understanding the dynamics of the fermion sea on the lattice, in particular for potentially non-trivial formulations such as with 2+1-flavor staggered fermions. We briefly describe details of a dynamical QCD calculation using improved staggered fermions, with 30,000 trajectories, that was run for our studies of flavour singlet mesons.

   hep-latPoS(2007)·5 citations
9. 09*

   Semileptonic D-decays and Lattice QCD

   Damir Becirevic🇫🇷 · Benjamin Haas🇫🇷 · Federico Mescia🇮🇹

   We explore four different strategies to extract the D-meson semileptonic decay form factors from the Green functions computed in QCD numerically on the lattice. From our numerical tests we find that two such strategies, based on the use of double ratios of 3-point correlation functions, lead to an appreciable reduction of systematic uncertainties. This is an important step in reducing the overall uncertainty in the lattice QCD results for the D-decay form factors which are needed to determine the CKM entries |Vcd| and |Vcs| experimentally, that are nowadays known by imposing the unitarity of the CKM matrix.

   hep-lathep-phPoS(2007)·12 citations
10. 10*

    Effective string theory description of the interface free energy

    M.Billo🇮🇹 · M.Caselle🇮🇹 · L.Ferro🇮🇹 · M.Hasenbusch🇮🇹 · M.Panero🇩🇪

    We compare the predictions of the Nambu-Goto effective string model with a set of high precision Monte Carlo results for interfaces with periodic boundary conditions in the 3D Ising model. We compute the free energy in the covariant gauge exactly, up to the inclusion of the Liouville mode. The perturbative expansion of this result agrees both with the result evaluated several years ago by Dietz and Filk in the physical gauge and with a recent calculation with the Polchinski-Strominger action. We also derive the effective string spectrum which, because of the different boundary conditions, is very different from the well known one of Arvis. Taking into proper account the effective string corrections and exploiting some technical improvements in the simulations we obtain precise estimate of the amplitude ratios T_c/\sqrt{sigma}, m_{0++}/\sqrt{\sigma} and sigma xi_{2nd}^2. We also discuss the behaviour of the effective string free energy in the dimensional reduction limit (i.e., near the deconfinement transition of the dual 3d gauge Ising model) and its relationship with the 2d Ising model interfaces

    hep-latPoS(2007)·5 citations
11. 11*

    Static potential for the quark-antiquark-gluon hybrid system in lattice QCD

    Marco Cardoso🇵🇹 · Pedro Bicudo🇵🇹 · Orlando Oliveira🇵🇹

    The static gluon-quark-antiquark interaction is investigated using lattice QCD techniques. A Wilson loop adequate to the static hybrid three-body system is developed and, using a $24^3\times 48$ periodic lattice with $\beta =6.2$, the potential energy of the system is measured for different geometries. For the medium range behaviour, when the quarks are far apart, we find a string tension which is compatible with two fundamental strings. On the other hand, when the quark and antiquark are nearby, the string tension is larger than two fundamental strings and is compatible with the Casimir scaling.

    hep-latPoS(2007)·9 citations
12. 12*

    Dynamical overlap fermions with increased topological tunnelling

    N. Cundy🇩🇪 · S. Krieg🇩🇪 · T. Lippert🇩🇪 · A Schaefer🇩🇪

    We present two improvements to our previous dynamical overlap HMC algorithm. We introduce a new method of differentiating the eigenvectors of the Kernel operator, which removes an instability in the fermionic force. Secondly, by simulating part of the fermion determinant exactly, without pseudo-fermions, we are able to increase the rate of topological tunnelling by a factor of more than ten, reducing the auto-correlation.

    hep-latPoS(2007)·11 citations
13. 13*

    Deflation Methods in Fermion Inverters

    Walter Wilcox🇺🇸

    I will review recent developments in matrix deflation methods, by Ronald Morgan/Walter Wilcox, Andreas Stathopoulos/Konstantinos Orginos, and Martin Lüscher, with application to lattice QCD fermion inversion. I will begin with a short review of deflation-related work in the field. The Morgan/Wilcox algorithms using GMRES and BiCGStab for deflation will be described. Typical results for quenched (Wilson and twisted mass) and dynamical configurations (CP-PACS and ETMC) will be displayed and discussed. I will outline how inclusion of multiple right-hand sides and multiple shifts can be accommodated within versions of these methods. I will also review deflation methods based on Conjugate Gradient introduced by Stathopoulos and Orginos for hermitian systems with multiple right-hand sides as well as Lüscher's non-hermitian domain decomposition algorithm using Generalized Conjugate Residual.}

    hep-latmath-phmath.MPPoS(2007)·19 citations
14. 14*

    Multi-Pion Systems in Lattice QCD and the Three-Pion Interaction

    Silas R. Beane🇺🇸 · William Detmold🇺🇸 · Thomas C. Luu🇺🇸 · Kostas Orginos🇺🇸 · Martin J. Savage🇺🇸 · Aaron Torok🇺🇸

    The ground-state energies of 2, 3, 4 and 5 \pi^+'s in a spatial volume V (2.5 fm)^3 are computed with lattice QCD. By eliminating the leading contribution from three-\pi^+ interactions, particular combinations of these n-\pi^+ ground-state energies provide precise extractions of the \pi^+\pi^+ scattering length in agreement with that obtained from calculations involving only two \pi^+'s. The three-\pi^+ interaction can be isolated by forming other combinations of the n-\pi^+ ground-state energies. We find a result that is consistent with a repulsive three-\pi^+ interaction for m_\pi < 352 MeV.

    hep-lathep-phnucl-thPRL(2008)·148 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.