Wed·Sep 17, 2003Wednesday·September 17, 2003

1. 01*

   Lattice Theories with Nonlinearly Realized Chiral Symmetry

   S. Chandrasekharan🇺🇸 · M. Pepe🇨🇭 · F. D. Steffen🇨🇭 · U.-J. Wiese🇨🇭

   We present the lattice formulation of effective Lagrangians in which chiral symmetry is realized nonlinearly on the fermion fields. In this framework both the Wilson term removing unphysical doubler fermions and the fermion mass term do not break chiral symmetry. Our lattice formulation allows us to address non-perturbative questions in effective theories of baryons interacting with pions and in models involving constitutent quarks interacting with pions and gluons. With the presented methods, a system containing a non-zero density of static baryons interacting with pions can be studied on the lattice without encountering a complex action problem. This might lead to new insights into the phase diagram of strongly interacting matter at non-zero chemical potential.

   hep-lathep-phnucl-thNucl.Phys.B Proc.Suppl.(2004)·7 citations
2. 02*

   Quark mass dependence of pseudoscalar masses and decay constants

   qq+q Collaboration · F. Farchioni (Munster U., ITP) · C. Gebert · I. Montvay · E. Scholz · L. Scorzato (DESY)

   The dependence of pseudo-scalar masses and decay constants on the sea and valence quark masses is investigated in the pseudo-Goldstone boson sector of QCD with two light quark flavours. The sea quark masses are at present in the range $1/3m_s\le m_{ud}\le 2/3m_s$ whereas the valence quark masses satisfy $1/2m_{sea}\le m_{val}\le 2m_{sea}$. The values of the Gasser-Leutwyler low energy constants $L_4$, $L_5$, $L_6$ and $L_8$ are estimated. The computation is done with the Wilson-quark lattice action at gauge coupling $\beta =5.1$ on $16^4$ lattices. $\mathcal{O}(a)$ effects are taken into account by applying chiral perturbation theory for the Wilson lattice action as proposed by Rupak and Shoresh.

   hep-latNucl.Phys.B Proc.Suppl.(2004)·4 citations
3. 03*

   Quantum chaos and regularity in ${\Phi }^4$ theory

   Helmut Kroeger🇨🇦 · Xiang-Qian Luo🇨🇳 · Harald Markum🇦🇹 · Rainer Pullirsch🇦🇹

   We check the eigenvalue spectrum of the ${\Phi }_{1+1}^4$ Hamiltonian against Poisson or Wigner behavior predicted from random matrix theory. We discuss random matrix theory as a tool to discriminate the validity of a model Hamiltonian compared to an analytically solvable Hamiltonian or experimental data.

   hep-latNucl.Phys.B Proc.Suppl.(2004)·0 citations
4. 04*

   Hardware and software status of QCDOC

   P.A. Boyle🇬🇧 · D. Chen · N.H. Christ🇺🇸 · M. Clark🇬🇧 · S.D. Cohen🇺🇸 · C. Cristian🇺🇸 · Z. Dong🇺🇸 · A. Gara🇺🇸 · B. Joo🇬🇧 · C. Jung🇺🇸 · C. Kim🇰🇷 · L. Levkova🇺🇸 and 7 other authors

   QCDOC is a massively parallel supercomputer whose processing nodes are based on an application-specific integrated circuit (ASIC). This ASIC was custom-designed so that crucial lattice QCD kernels achieve an overall sustained performance of 50% on machines with several 10,000 nodes. This strong scalability, together with low power consumption and a price/performance ratio of $1 per sustained MFlops, enable QCDOC to attack the most demanding lattice QCD problems. The first ASICs became available in June of 2003, and the testing performed so far has shown all systems functioning according to specification. We review the hardware and software status of QCDOC and present performance figures obtained in real hardware as well as in simulation.

   hep-latNucl.Phys.B Proc.Suppl.(2004)·15 citations
5. 05*

   Theory and Phenomenology of the Polyakov loop in QCD Thermodynamics

   Peter N. Meisinger🇺🇸 · Travis R. Miller🇺🇸 · Michael C. Ogilvie🇺🇸

   A synthesis of Polyakov loop models of the deconfinement transition and quasiparticle models of gluon plasma thermodynamics leads to a class of models in which gluons move in a non-trivial Polyakov loop background. These models are successful candidates for explaining both critical behavior and the equation of state for the SU(3) gauge theory at finite temperature. Two sensitive lattice probes which can discriminate between models are the Polyakov loop P and e-3p.

   hep-lathep-phnucl-thNucl.Phys.B Proc.Suppl.(2004)·7 citations
6. 06*

   Chiral and Critical Behavior in Strong Coupling QCD

   Shailesh Chandrasekharan🇺🇸

   We use a cluster algorithm to study the critical behavior of strongly coupled lattice QCD in the chiral limit. We show that the finite temperature chiral phase transition belongs to the O(2) universality class as expected. When we compute the finite size effects of the chiral susceptibility in the low temperature phase close to the transition, we find clear evidence for chiral singularities predicted by chiral perturbation theory (ChPT). On the other hand it is difficult to reconcile the quark mass dependence of various quantities near the chiral limit with ChPT.

   hep-latNucl.Phys.B Proc.Suppl.(2004)·0 citations
7. 07*

   Recent Developments in Lattice Supersymmetry

   David B. Kaplan🇺🇸

   I discuss a new approach to constructing lattices for gauge theories with extended supersymmetry. The lattice theories themselves respect certain supersymmetries, which in many cases allows the target theory to be obtained in the continuum limit without fine-tuning.

   hep-latNucl.Phys.B Proc.Suppl.(2004)·59 citations
8. 08*

   Four-momentum boosted Fermion fields

   P. Boyle🇬🇧

   A formulation of the fermion action is discussed which includes an explicit four momentum boost on the field prior to discretisation. This is used to shift the zero of lattice momentum to lie near one of the on-shell quark poles. The positive pole is selected if we wish to describe a valence quark, and negative pole for a valence anti-quark. Like NRQCD, the typical lattice momenta involved in hadronic correlation functions can be kept small: of order $O(a{\Lambda }_{\mathrm{QCD}})$, rather than $O(a{m}_Q)$ even when describing heavy quarks. If we expand around the particle pole, the anti-particle correlator will be poorly described for large $a{m}_Q$. However, in that case the anti-particle will be far off shell and will only affect unphysical, renormalization factors. The formulation produces the correct continuum limit, and preliminary results have been obtained (for an unimproved action) of both the one-loop self energy and a non-perturbative correlation function.

   hep-latNucl.Phys.B Proc.Suppl.(2004)·9 citations
9. 09*

   Analytic estimates of quenched penguins

   Maarten Golterman (SFSU)🇺🇸 · Santi Peris (UAB)🇪🇸

   When we embed the strong penguin operator Q_6 in the quenched theory, it does not remain a singlet under right-handed chiral transformations. As a consequence, more low-energy constants associated with this operator appear than in the unquenched theory. We give analytic estimates of the leading constants. The results suggest that the effects of quenching on this operator are large.

   hep-latNucl.Phys.B Proc.Suppl.(2004)·5 citations
10. 10*

    MEM Analysis of Glueball Correlators at T>0

    Noriyoshi Ishii (Wako, RIKEN)🇯🇵 · Hideo Suganuma (Tokyo Inst. Tech.)🇯🇵

    Maximum Entropy Method (MEM) is applied to glueball correlators at finite temperature constructed by using 5,500-9,900 gauge field configurations generated in SU(3) quenched lattice QCD with the lattice parameter beta = 2N_c/g^2 = 6.25 and the renormalized anisotropy a_s/a_t = 4. The results support the thermal width broadening of the 0++ glueball near the critical temperature.

    hep-latNucl.Phys.B Proc.Suppl.(2004)·6 citations
11. 11*

    Positivity and Fermionic Dense Matter

    Deog Ki Hong (Pusan Nat'l U.)🇰🇷 · Stephen D. H. Hsu (U. of Oregon)🇺🇸

    Euclidean dense matter generically suffers from the fermion sign problem. However, we argue that the sign problem is absent if one considers only low-energy degrees of freedom. Specifically, the low energy effective theory of dense QCD has positive Euclidean path integral measure, which allows one to establish rigorous inequalities showing that the color-flavor locked (CFL) phase is the true vacuum of three flavor, massless QCD. We then describe a method for simulating dense QCD on the lattice. We also discuss applications to electronic systems in condensed matter, such as generalized Hubbard models.

    hep-lathep-phhep-thNucl.Phys.B Proc.Suppl.(2004)·3 citations
12. 12*

    Lattice Study of the Massive Schwinger Model with a $\theta$ term under Lüscher's "Admissibility" condition

    Hidenori Fukaya🇯🇵 · Tetsuya Onogi (YITP, Kyoto Univ.)🇯🇵

    We present a numerical study of the massive two-flavor QED in two dimensions with the gauge action proposed by Lüscher, which allows only ``admissible'' gauge fields. We find that the admissibility condition does not allow any topology changes by the local updation in Hybrid Monte Carlo algorithm so that the configurations in each topological sector can be generated separately. By developing a new method to sum over different topological sectors, we investigate $\theta$ vacuum effects. Combining with domain-wall fermion action, we obtain the fermion mass dependence and $\theta$ dependence of the meson masses, which are consistent with the analytic results by mass perturbation in the continuum theory.

    hep-latNucl.Phys.B Proc.Suppl.(2004)·0 citations
13. 13*

    Calculating weak matrix elements using HYP staggered fermions

    T.Bhattacharya🇺🇸 · G.T.Fleming🇺🇸 · G.Kilcup🇺🇸 · R.Gupta🇺🇸 · W.Lee🇰🇷 · S.Sharpe🇺🇸

    We present preliminary results of weak matrix elements relevant to CP violation calculated using the HYP (II) staggered fermions. Since the complete set of matching coefficients at the one-loop level became available recently, we have constructed lattice operators with all the $g^2$ corrections included. The main results include both $\Delta I=3/2$ and $\Delta I=1/2$ contributions.

    hep-latNucl.Phys.B Proc.Suppl.(2004)·5 citations
14. 14*

    Searching for KvBLL calorons in SU(3) lattice gauge field ensembles

    Christof Gattringer🇩🇪 · Ernst-Michael Ilgenfritz🇩🇪 · Boris V. Martemyanov🇷🇺 · Michael Müller-Preussker🇩🇪 · Dirk Peschka🇩🇪 · Rainer Pullirsch🇩🇪 · Stefan Schaefer🇩🇪 · Andreas Schäfer🇩🇪

    We discuss Kraan - van Baal - Lee - Lu (KvBLL) solutions of the classical Yang-Mills equations with temperature in the context of SU(3) lattice gauge theory. We present discretized lattice versions of KvBLL solutions and other dyonic structures, obtained by cooling in order to understand their variety and signature. An analysis of the zero modes of the lattice Dirac operator for different fermionic boundary conditions gives clear evidence for a KvBLL-like background of finite T lattice subensembles with Q = +/-1. Using APE-smearing we are able to study the topological charge density q(x) of the configurations and to corroborate this interpretation.

    hep-latNucl.Phys.B Proc.Suppl.(2004)·32 citations
15. 15*

    Semileptonic decays of $D$ mesons in unquenched lattice QCD

    Masataka Okamoto🇯🇵 · Massimo di Pierro🇺🇸 · Aida X. El-Khadra🇺🇸 · Steven Gottlieb🇺🇸 · Andreas S. Kronfeld🇺🇸 · Paul B. Mackenzie🇺🇸 · Damian P. Menscher🇺🇸 · Mehmet B. Oktay🇺🇸 · James N. Simone🇺🇸

    We present our preliminary results for semileptonic form factors of $D$ mesons in unquenched lattice QCD. Simulations are carried out with $n_f=2+1$ dynamical quarks using gauge configurations generated by the MILC collaboration. For the valence quarks, we adopt an improved staggered light quark action and the clover heavy quark action. Our results for $D\to K$ and $D\to \pi$ form factors at $q^2=0$ are in agreement with the experimental values.

    hep-latNucl.Phys.B Proc.Suppl.(2004)·33 citations
16. 16*

    Preliminary results in unquenched Numerical Stochastic Perturbation Theory

    F. Di Renzo🇮🇹 · A. Mantovi🇮🇹 · V. Miccio (Parma Univ.)🇮🇹 · L. Scorzato (DESY)🇩🇪

    Introducing fermionic loops contributions in Numerical Stochastic Perturbation Theory was mainly motivated by the proposal to compute 2-3 loops for renormalization constants (and improvement coefficients). This is feasible because the computational overhead of unquenching NSPT is by far lower than for non perturbative simulations. We report on first, preliminary results for the quark propagator (basically the third loop for the critical mass) and discuss the status of the computation of other quantities.

    hep-latNucl.Phys.B Proc.Suppl.(2004)·0 citations
17. 17*

    The phase diagram of N_f=3 QCD for small baryon densities

    Ph. de Forcrand (CERN, ETH Zurich)🇨🇭 · O. Philipsen (MIT)🇺🇸

    We demonstrate how to locate the critical endpoint of the QCD phase transition by means of simulations at imaginary \mu. For the three flavor theory, we present numerical results for the pseudo-critical line as a function of chemical potential and bare quark mass, as well as the bare quark mass dependence of the endpoint.

    hep-latNucl.Phys.B Proc.Suppl.(2004)·37 citations
18. 18*

    SU(2) Glueballs, diquarks and mesons in dense matter

    M.-P. Lombardo🇮🇹 · M. L. Paciello🇮🇹 · S. Petrarca🇮🇹 · B. Taglienti🇮🇹

    We present preliminary results from a high statistics study of 2-color QCD at low temperature and non-zero baryon density. The simulations are carried out on a 6^3*12 lattice and use a standard hybrid molecular dynamics algorithm for staggered fermions for two values of quark mass. Observables include glueball correlators evaluated via a multi-step smearing procedure as well as scalar and vector mesons and diquarks.

    hep-latNucl.Phys.B Proc.Suppl.(2004)·6 citations
19. 19*

    Four loop stochastic perturbation theory in 3d SU(3)

    F. Di Renzo🇮🇹 · A. Mantovi🇮🇹 · V. Miccio (Parma Univ.)🇮🇹 · Y. Schroder (MIT-CTP)🇺🇸

    Dimensional reduction is a key issue in finite temperature field theory. For example, when following the QCD Free Energy from low to high scales across the critical temperature, ultrasoft degrees of freedom can be captured by a 3d SU(3) pure gauge theory. For such a theory a complete perturbative matching requires four loop computations, which we undertook by means of Numerical Stochastic Perturbation Theory. We report on the computation of the pure gauge plaquette in 3d, and in particular on the extraction of the logarithmic divergence at order g^8, which had already been computed in the continuum.

    hep-latNucl.Phys.B Proc.Suppl.(2004)·5 citations
20. 20*

    Tackling the infrared problem of thermal QCD

    Y. Schroder (MIT, LNS)🇺🇸

    Perturbative calculations of corrections to the behavior of an ideal gas of quarks and gluons, the limit that is formally realized at infinite temperature, are obstructed by severe infrared divergences. The limits to computability that the infrared problem poses can be overcome in the framework of dimensionally reduced effective theories. Here, we give details on the evaluation of the highest perturbative coefficient needed for this setup, in the continuum.

    hep-lathep-phNucl.Phys.B Proc.Suppl.(2004)·16 citations
21. 21*

    Nucleon axial charge and structure functions with domain wall fermions

    Shigemi Ohta (1 and 2)🇯🇵 · Kostas Orginos (2) (for the RBCK Collaboration) ((1) Institute of Particle and Nuclear Studies, KEK, (2) RIKEN BNL Research Center, BNL)🇺🇸

    We report the current status of RBCK calculations on nucleon structure with both quenched and unquenched lattice QCD. The combination of domain wall fermions and DBW2 gauge action works well for isovector vector and axial charges, and moments of structure functions <x>_q, d_1, and <1>_{\delta q}.

    hep-latNucl.Phys.B Proc.Suppl.(2004)·11 citations
22. 22*

    QCD Critical Region and Quark Gluon Plasma from an Imaginary mu_B

    Massimo D'Elia🇮🇹 · Maria-Paola Lombardo🇮🇹

    We discuss the imaginary chemical potential approach to the study of QCD at nonzero temperature and density, present results for the four flavor model in the different phases and show that this method is ideally suited for a comparison between lattice data and phenomenological models.

    hep-latNucl.Phys.B Proc.Suppl.(2004)·8 citations
23. 23*

    Baryons and confining strings

    Oliver Jahn (ETH Zurich & MIT)🇨🇭 · Philippe de Forcrand (ETH Zurich & CERN)🇨🇭

    The subleading term of the heavy quark potential (the analogue of the Luscher term) is computed in a string model for the case of three quarks. It turns out to be positive in 2+1 dimensions, making the potential non-concave as a function of the scale for fixed geometry. The results are compared to numerical simulations of the lattice gauge theory.

    hep-latNucl.Phys.B Proc.Suppl.(2004)·35 citations
24. 24*

    Where is the chiral critical point in 3-flavor QCD?

    F. Karsch🇩🇪 · C.R. Allton🇬🇧 · S. Ejiri🇩🇪 · S.J. Hands🇬🇧 · O. Kaczmarek🇩🇪 · E. Laermann🇩🇪 · C. Schmidt🇩🇪

    We determine the location of the second order endpoint of the line of first order chiral phase transition in 3-flavor QCD at vanishing chemical potential. Using Ferrenberg-Swendsen reweighting for two values of the quark mass we determine the dependence of the transition line on the chemical potential and locate the chiral critical point. For both quantities we find a significant quark mass dependence.

    hep-latNucl.Phys.B Proc.Suppl.(2004)·179 citations
25. 25*

    Matrix Model and Ginsparg-Wilson Relation

    Keiichi Nagao🇯🇵

    We discuss that the Ginsparg-Wilson relation, which has the key role in the recent development of constructing lattice chiral gauge theory, can play an important role to define chiral structures in finite matrix models and noncommutative geometries.

    ↳ hep-thhep-latNucl.Phys.B Proc.Suppl.(2004)·9 citations
26. 26*

    Dimensional Reduction of Fermions in Brane Worlds of the Gross-Neveu Model

    W. Bietenholz🇩🇪 · A. Gfeller🇨🇭 · U.-J. Wiese🇨🇭

    We study the dimensional reduction of fermions, both in the symmetric and in the broken phase of the 3-d Gross-Neveu model at large N. In particular, in the broken phase we construct an exact solution for a stable brane world consisting of a domain wall and an anti-wall. A left-handed 2-d fermion localized on the domain wall and a right-handed fermion localized on the anti-wall communicate with each other through the 3-d bulk. In this way they are bound together to form a Dirac fermion of mass m. As a consequence of asymptotic freedom of the 2-d Gross-Neveu model, the 2-d correlation length \xi = 1/m increases exponentially with the brane separation. Hence, from the low-energy point of view of a 2-d observer, the separation of the branes appears very small and the world becomes indistinguishable from a 2-d space-time. Our toy model provides a mechanism for brane stabilization: branes made of fermions may be stable due to their baryon asymmetry. Ironically, our brane world is stable only if it has an extreme baryon asymmetry with all states in this ``world'' being completely filled.

    ↳ hep-thhep-latJHEP(2003)·23 citations
27. 27*

    Extracting physics from an unphysical situation: light mesons in a small box

    W. Bietenholz🇩🇪 · S. Capitani🇦🇹 · T. Chiarappa🇩🇪 · M. Hasenbusch🇩🇪 · K. Jansen🇩🇪 · M. Muller-Preussker🇩🇪 · K.-I. Nagai🇩🇪 · M. Papinutto🇩🇪 · S. Shcheredin🇩🇪 · A. Shindler🇩🇪 · C. Urbach🇩🇪 · I. Wetzorke🇩🇪

    Quantum Chromo Dynamics is considered in a setup where the light mesons are squeezed into unphysically small boxes. We show how such a situation can be used to determine the couplings of the low energy chiral Lagrangian from lattice simulations, applying chirally invariant formulations of lattice fermions.

    ↳ physics.comp-phhep-lathep-ph1 citation

* 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.