HEP Lattice·hep-lat
9 papers—8 primary·1 cross-listed·reconstructed*
Kazuo Fujikawa🇯🇵 · Masato Ishibashi🇯🇵
A new class of lattice Dirac operators have been recently proposed on the basis of the generalized Ginsparg-Wilson relation, , where is a non-negative integer. We discuss the index theorem and locality properties for this general class of lattice Dirac operators.
K. Langfeld🇩🇪 · E.-M. Ilgenfritz🇯🇵 · H. Reinhardt🇩🇪 · G. Shin🇩🇪
The continuum limit of SU(2) lattice gauge theory is carefully investigated at zero and at finite temperatures. It is found that the continuum gauge field has singularities originating from center degrees of freedom being discovered in Landau gauge. Our numerical results show that the density of these singularities properly extrapolates to a non-vanishing continuum limit. The action density of the non-trivial Z_2 links is tentatively identified with the gluon condensate. We find for temperatures larger than the deconfinement temperature that the thermal fluctuations of the embedded Z_2 gauge theory result in an increase of the gluon condensate with increasing temperature.
K. Langfeld🇩🇪 · H. Reinhardt🇩🇪 · J. Gattnar🇩🇪
The gluon propagator in Landau gauge is calculated on the lattice for SU(2) gauge theory. In particular the manifestation of confinement in the gluon propagator is studied. Removing the confining center vortices from the Yang-Mills ensemble leads to a drastic reduction of the gluonic form factor in the intermediate momentum regime.
L. Dittmann🇩🇪 · T. Heinzl🇩🇪 · A. Wipf🇩🇪
We perform a lattice analysis of the Faddeev-Niemi effective action conjectured to describe the low energy sector of SU(2) Yang-Mills theory. We generalize the effective action such that it contains all operators built from a unit color vector field n with O(3)-symmetry and maximally four derivatives. To avoid the presence of Goldstone bosons, we include explicit symmetry breaking terms parametrized by an external field h of mass-dimension two. We find a mass gap of the order of 1.5 GeV.
In the presence of a non-vanishing chemical potential the eigenvalues of the Dirac operator become complex. We use a random matrix model approach to calculate analytically all correlation functions at weak and strong non-Hermiticity for three-dimensional QCD with broken flavor symmetry and four-dimensional QCD in the bulk.
P.H. Damgaard🇨🇭 · U.M. Heller🇺🇸 · R. Niclasen🇩🇰 · B. Svetitsky🇮🇱
It has been conjectured that spontaneous chiral symmetry breaking in strongly coupled vectorlike gauge theories falls into only three different classes, depending on the gauge group and the representations carried by the fermions. We test this proposal by studying SU(2), SU(3) and SU(4) lattice gauge theories with staggered fermions in different irreducible representations. Staggered fermions away from the continuum limit should, for all complex representations, still belong to the continuum class of spontaneous symmetry breaking. But for all real and pseudo-real representations we show that staggered fermions should belong to incorrect symmetry breaking classes away from the continuum, thus generalizing previous results. As an unambiguous signal for whether chiral symmetry breaks, and which breaking pattern it follows, we look at the smallest Dirac eigenvalue distributions. We find that the patterns of symmetry breaking are precisely those conjectured.
Derek J. Hepburn · UKQCD Collaboration
I present results of recent work for the UKQCD Collaboration on the light hadron spectrum using a non-perturbatively O(a)-improved Wilson action with two degenerate flavours of dynamical quarks on a 16^3x32 lattice. Values of the bare gauge coupling and bare dynamical quark mass were chosen to keep the lattice spacing fixed at two distinct values in physical units as determined through the Sommer scale parameter, r0. I also include results for a quenched ensemble with a lattice spacing matching one of these dynamical sets and results from an exploratory run at lighter bare quark mass.
C. Bernard🇺🇸 · T. Burch🇺🇸 · S. Datta🇺🇸 · T.A. DeGrand🇺🇸 · C.E. DeTar🇺🇸 · Steven Gottlieb🇺🇸 · U.M. Heller🇺🇸 · K. Orginos🇺🇸 · R.L. Sugar🇺🇸 · D. Toussaint🇺🇸
We present preliminary results from exploring the phase diagram of finite temperature QCD with three degenerate flavors and with two light flavors and the mass of the third held approximately at the strange quark mass. We use an order Symanzik improved gauge action and an order improved staggered quark action. The improved staggered action leads to a dispersion relation with diminished lattice artifacts, and hence better thermodynamic properties. It decreases the flavor symmetry breaking of staggered quarks substantially, and we estimate that at the transition temperature for an to lattice {\em all} pions will be lighter than the lightest kaon. Preliminary results on lattices with , 6 and 8 are presented.
The present status of the theoretical estimates of the difference between the widths of the neutral Bs-mesons and of the B-meson lifetime ratios is reviewed. In particular, the lattice results for the matrix elements of the relevant (delta B=2)-operators are updated and the first lattice QCD results for the matrix elements of (delta B=0)-operators are presented. In both cases, the NLO perturbative QCD corrections in the coefficient functions have been included. The theoretically updated results are: (delta Gamma/Gamma)_{Bs} = (7 +/- 4) %, tau(B+)/tau(Bd) = 1.07(3) and tau(Bs)/tau(Bd) = 1.00(2).
* 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.