HEP Lattice·hep-lat
22 papers—20 primary·2 cross-listed·reconstructed*
M. Nobes🇨🇦 · H. Trottier🇨🇦 · G.P. Lepage🇺🇸 · Q. Mason🇺🇸
We present the results of our perturbative calculations of the static quark potential, small Wilson loops, the static quark self energy, and the mean link in Landau gauge. These calculations are done for the one loop Symanzik improved gluon action, and the improved staggered quark action.
Shoichi Sasaki (Univ. of Tokyo)🇯🇵
Domain wall fermions (DWF) are a new fermion discretization scheme with greatly improved chiral symmetry. Our final goal is to study the nucleon spin structure through lattice simulation using DWF. In this paper, we present our current progress on two topics toward this goal: 1) the mass spectrum of the nucleon excited states and 2) the iso-vector vector and axial charges, and , of the nucleon.
Shoichi Sasaki (1 and 2)🇯🇵 · Tom Blum (2)🇺🇸 · Shigemi Ohta (3 and 2)🇯🇵 · Kostas Orginos(2) ((1) Univ. of Tokyo, (2) RIKEN BNL, (3) KEK)🇺🇸
In our previous DWF calculation with the Wilson gauge action at ( 1.9 GeV) on a lattice, we found that had a fairly strong dependence on the quark mass. A simple linear extrapolation of to the chiral limit yielded a value that was almost a factor of two smaller than the experimental one. Here we report our recent study of this issue. In particular, we investigate possible errors arising from finite lattice volume, especially in the lighter quark mass region. We employ a RG-improved gauge action (DBW2), which maintains very good chiral behavior even on a coarse lattice ( 1.3 GeV), in order to perform simulations at large physical volume (). Our preliminary results suggest that the finite volume effect is significant.
The deconfinement transition in SU(4) lattice gauge theory is studied on N_s^3 X N_t lattices with N_s = 8-16 and N_t = 4-8 using a modified Wilson action which is expected to have no bulk transitions. The peak of susceptibility \chi_{|L|} is found to increase linearly with spatial volume for N_t = 4, 5, and 6, indicating a first order deconfinement phase transition. The latent heat is estimated to be approximately 2/3 of the corresponding ideal gas energy density at T_c.
K. Langfeld🇩🇪 · E.-M. Ilgenfritz🇯🇵 · H. Reinhardt🇩🇪 · A. Schäfke🇩🇪
We consider a new cooling procedure which separates gluon degrees of freedom from singular center vortices in SU(2) LGT in a gauge invariant way. Restricted by a cooling scale fixing the residual SO(3) gluonic action relative to the string tension, the procedure is RG invariant. In the limit a pure Z(2) vortex texture is left. This {\it minimal} vortex content does not contribute to the string tension. It reproduces, however, the lowest glueball states. With an action density scaling like with , it defines a finite contribution to the action density at T=0 in the continuum limit. We propose to interpret this a mass dimension 4 condensate related to the gluon condensate. Similarly, this vortex texture is revealed in the Landau gauge.
Matteo Beccaria🇮🇹 · Massimo Campostrini🇮🇹 · Alessandra Feo🇩🇪
We study a Hamiltonian lattice version of the two-dimensional Wess-Zumino model. Preliminary results obtained by Quantum Monte Carlo with a many-parameter guiding wave function are presented. We analyze the pattern of supersymmetry breaking by measuring the ground state energy and a set of supersymmetric Ward identities. The algorithm is quite effective and allows very precise measurements.
M. Göckeler🇩🇪 · R. Horsley🇩🇪 · D. Pleiter🇩🇪 · P.E.L. Rakow🇩🇪 · S. Schaefer🇩🇪 · A. Schäfer🇩🇪 · G. Schierholz🇩🇪
It has been suggested to use the production of Lambda hyperons for investigating the nucleon spin structure. The viability of this idea depends crucially on the spin structure of the Lambda. Using nonperturbatively O(a) improved Wilson fermions in the quenched approximation we have studied matrix elements of two-quark operators in the Lambda. We present results for the axial vector current, which give us the contributions of the u, d, and s quarks to the Lambda spin.
J.M. Carmona🇪🇸 · M. D'Elia🇮🇹 · L. Del Debbio🇮🇹 · A. Di Giacomo🇮🇹 · B. Lucini🇬🇧 · G. Paffuti🇮🇹
A disorder parameter detecting dual superconductivity of the vacuum is measured across the chiral phase transition in full QCD with two flavours of dynamical staggered fermions. The observed behaviour is similar to the quenched case.
T. Suzuki🇯🇵 · Y. Koma🇯🇵 · S. Ito🇯🇵 · E.-M. Ilgenfritz🇯🇵 · T.W. Park🇯🇵 · M.I. Polikarpov🇷🇺 · T. Yazawa🇯🇵
Three topics of monopole dynamics in gluodynamics are presented. 1)Gauge (in)dependence of the monopole effective action (S.Ito, T.W.Park, T.Suzuki): Four different abelian projections are studied. MA and Laplacian abelian gauges show almost the same renormalization flow and renormalized trajectory. 2)The quantized dual abelian Higgs model (DAH) derived from SU(2) gluodynamics and its vacuum structure (Y.Koma, E.-M.Ilgenfritz, T.Suzuki,M.I.Polikarpov): Monte-Carlo analysis of DAH is done. The quantum average of the dual field strength shows a flux tube profile similar to the color-electric field profile measured in SU(2) gluodynamics. 3)Lattice instanton action from 3D SU(2) Georgi-Glashow model (GG) (T.Yazawa, T.Suzuki): (GG) is studied on the lattice in the London limit. We determine an effective instanton action both in unitary and MA gauges. For some range of parameters, we obtain almost perfect actions which look the same in both gauges (gauge independence) and which reproduce well the string tension.
The potential of a static quark-antiquark pair is studied in the range 0.05 fm r 0.8 fm, employing a sequence of lattices up to 64^4. The continuum quantities are evaluated by extrapolation of the data at finite lattice spacing. The results are compared with the perturbation theory predictions obtained from the solution of the renormalization group equation for the coupling. The renormalization scheme must be chosen carefully. No evidence for large non-perturbative effects at short distances is seen.
A. Di Giacomo🇮🇹 · G. Paffuti🇮🇹
We demonstrate that the disorder parameter to detect dual superconductivity in the confining phase of QCD is the v.e.v. of a magnetically charged, Dirac like, gauge invariant operator . We also show that the abelian projection on the lattice is determined up to terms O(a^2) (a = lattice spacing).
K. Kajantie🇫🇮 · M. Laine🇨🇭 · T. Neuhaus🇩🇪 · A. Rajantie🇬🇧 · K. Rummukainen🇸🇪
We study the critical behaviour of the three-dimensional U(1) gauge+Higgs theory (Ginzburg-Landau model) at large scalar self-coupling \lambda (``type II region'') by measuring various correlation lengths as well as the Abrikosov-Nielsen-Olesen vortex tension. We identify different scaling regions as the transition is approached from below, and carry out detailed comparisons with the criticality of the 3d O(2) symmetric scalar theory.
L.Bogacz🇩🇪 · Z.Burda🇩🇪 · J.Jurkiewicz🇵🇱 · A.Krzywicki🇫🇷 · C.Petersen🇩🇪 · B.Petersson🇩🇪
Lattice formulation of a fermionic field theory defined on a randomly triangulated compact manifold is discussed, with emphasis on the topological problem of defining spin structures on the manifold. An explicit construction is presented for the two-dimensional case and its relation with the Ising model is discussed. Furthermore, an exact realization of the Kramers-Wannier duality for the two-dimensional Ising model on the manifold is considered. The global properties of the field are discussed. The importance of the GSO projection is stressed. This projection has to be performed for the duality to hold.
Ferdinando Gliozzi🇮🇹 · Antonio Rago🇮🇹
The normal confining phase of gauge theories is characterised by the condensation of magnetic monopoles and center vortices. Sometimes in coupled gauge system one finds another phase with simultaneous condensation of electric and magnetic charges. In both phases the confining string breaks down at a given scale because of pair creation, however the mechanism is different. In the former case the string breaking is a mixing phenomenon which is invisible in the Wilson loop. On the contrary, in presence of both electric and magnetic condensates the string breaking can be observed even in the Wilson loops. Numerical experiments on a 3D gauge-Higgs system neatly show this new phenomenon.
To verify the conjecture that Yang-Mills theory in the infrared limit is equivalent to a spin system whose excitations are knot solitons, a numerical algorithm based on the inverse Monte Carlo method is proposed. To investigate the stability of the effective spin field action, numerical studies of the renormalization group flow for the coupling constants are suggested. A universality of the effective spin field action is also discussed.
Roman Bertle🇦🇹 · Michael Engelhardt🇩🇪 · Manfried Faber🇦🇹
We determine the topological susceptibility from center projected vortices and demonstrate that the topological properties of the SU(2) Yang-Mills vacuum can be extracted from the vortex content. We eliminate spurious ultraviolet fluctuations by two different smoothing procedures. The extracted susceptibility is comparable to that obtained from full field configurations.
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.
Sergio Caracciolo🇮🇹 · Andrea Pelissetto🇮🇹 · Antonio Rago🇮🇹
We test an algebraic algorithm based on the coordinate-space method, evaluating with high accuracy the critical mass for Wilson fermions in lattice QCD at two loops. We test the results by using different types of infrared regularization.
Sergio Caracciolo🇮🇹 · Andrea Montanari🇫🇷 · Andrea Pelissetto🇮🇹
We consider a two-dimensional sigma-model with discrete icosahedral/dodecahedral symmetry. We present high-precision finite-size numerical results that show that the continuum limit of this model is different from the continuum limit of the rotationally invariant O(3) sigma-model.
A. Borici🇬🇧 · A. D. Kennedy🇬🇧 · B. J. Pendleton🇬🇧 · U. Wenger🇬🇧
We use a continued fraction expansion of the sign-function in order to obtain a five dimensional formulation of the overlap lattice Dirac operator. Within this formulation the inverse of the overlap operator can be calculated by a single Krylov space method where nested conjugate gradient procedures are avoided. We show that the five dimensional linear system can be made well conditioned using equivalence transformations on the continued fractions. This is of significant importance when dynamical overlap fermions are simulated.
Ph. Boucaud🇫🇷 · J.P. Leroy🇫🇷 · J. Micheli🇫🇷 · H. Moutarde🇫🇷 · O. Pene🇫🇷 · J. Rodriguez-Quintero🇪🇸 · C. Roiesnel🇫🇷
We present preliminary results on the computation of the QCD running coupling constant in the MOM_tilde scheme and Landau gauge with two flavours of dynamical Wilson quarks. Gluon momenta range up to about 7 GeV (beta=5.6, 5.8 and 6.0) with a constant dynamical quark mass. This range already allows to exhibit some evidence for a sizeable 1/mu^2 correction to the asymptotic behaviour, as in the quenched approximation. We find Lambda_MS^(N_f=2) = 264(27) MeV x [a^{-1}(5.6,0.1560)/(2.19 GeV)], which leads to alpha_s(M_Z) = 0.113(3)(4). In view of the systematics error to be controlled, this encouraging result is more a preliminary indication than a real prediction.
D. Becirevic🇮🇹 · Ph. Boucaud🇫🇷 · F. De Soto🇪🇸 · A. Le Yaouanc🇫🇷 · J.P. Leroy🇫🇷 · J. Micheli🇫🇷 · O. Pène🇫🇷 · J Rodrí guez-Quintero🇪🇸 · C. Roiesnel🇫🇷
We show that QCD Green functions in Landau Gauge exhibit sizable corrections to the expected perturbative behavior at energies as high as 10 GeV. We argue that these are due to a -condensate which does not vanish in Landau gauge.
* 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.