HEP Lattice·hep-lat

Fri·Sep 30, 2005Friday·September 30, 2005

12 papers—11 primary·1 cross-listed·reconstructed*

01*
Testing Topology Conserving Gauge Actions for Lattice QCD
K.-i. Nagai🇩🇪 · K. Jansen (NIC/DESY-Zeuthen)🇩🇪 · W. Bietenholz🇩🇪 · L. Scorzato (Humboldt Univ. zu Berlin)🇩🇪 · S. Necco (CPT, Marseille)🇫🇷 · S. Shcheredin (Univ. Bielefeld)🇩🇪
We explore gauge actions for lattice QCD, which are constructed such that the occurrence of small plaquette values is strongly suppressed. Such actions originate from the admissibility condition in order to conserve the topological charge. The suppression of small plaquette values is expected to be advantageous for numerical studies in the $ϵ$ -regime and also for simulations with dynamical quarks. Performing simulations at a lattice spacing of about 0.1 fm, we present numerical results for the static potential, the physical scale $r_{0}$ , the stability of the topological charge history, the condition number of the kernel of the overlap operator and the acceptance rate against the step size in the local HMC algorithm.
hep-latPoS(2006)·3 citations
02*
Topological clusters in SU(2) gluodynamics at finite temperature and the evidence for KvB calorons
E.-M.Ilgenfritz🇩🇪 · P. Gerhold🇩🇪 · M. Müller-Preussker (Humboldt Universität Berlin)🇩🇪 · B.V. Martemyanov🇷🇺 · A.I. Veselov (ITEP Moscow)🇷🇺
We report on our search for Kraan-van Baal calorons in finite temperature SU(2) lattice ensembles. We also discuss recent progress made in developing a caloron-anticaloron gas model decribing confinement and deconfinement in the context of trivial and non-trivial holonomy.
hep-latPoS(2006)·2 citations
03*
Pseudoscalar Mass and Decay Constant in Lattice QCD with Exact Chiral Symmetry
Ting-Wai Chiu🇹🇼 · Tung-Han Hsieh🇹🇼 · Jon-Yu Lee🇹🇼 · Pei-Hua Liu🇹🇼 · Hsiu-Ju Chang🇹🇼
The masses and decay constants of pseudoscalar mesons $D$ , $D_{s}$ , and $K$ are determined in quenched lattice QCD with exact chiral symmetry. For 100 gauge configurations generated with single-plaquette action at $β = 6.1$ on the $2 0^{3} \times 40$ lattice, we compute point-to-point quark propagators for 30 quark masses in the range $0.03 \leq m_{q} a \leq 0.80$ , and measure the time-correlation functions of pseudoscalar and vector mesons. The inverse lattice spacing $a^{- 1}$ is determined with the experimental input of $f_{π}$ , while the strange quark bare mass ( $m_{s} a = 0.08$ ), and the charm quark bare mass ( $m_{c} a = 0.80$ ) are fixed such that the masses of the corresponding vector mesons are in good agreement with $ϕ (1020)$ and $J / ψ (3097)$ respectively. Our results of pseudoscalar-meson decay constant are: $f_{K} = 152 (6) (10)$ MeV, $f_{D} = 235 (8) (14)$ MeV, and $f_{D_{s}} = 266 (10) (18)$ MeV [hep-ph/0506266]. The latest experimental result of $f_{D^{+}}$ from CLEO [hep-ex/0508057] is in good agreement with our prediction.
hep-lathep-exhep-phPoS(2006)·3 citations
04*
A quenched study of m_b in HQET beyond the leading order
Michele Della Morte🇩🇪 · Nicolas Garron🇩🇪 · Rainer Sommer🇩🇪 · Mauro Papinutto🇩🇪
A non perturbative method to compute the mass of the b quark including the 1/m term in HQET has been presented in a companion talk. Following this strategy, we find in the MS bar scheme m_b^{stat}(m_b) = 4.350(64) GeV for the leading term, and m_b^{(1)}(m_b) = -0.049(29) GeV for the next to leading order correction. This method involves several steps, including the simulation of the relativistic theory in a small volume, and of the effective theory in a big volume. Here we present some numerical details of our calculations.
hep-latPoS(2006)·4 citations
05*
Testing Fermion Actions: Scaling in the Schwinger Model
Nils Christian🇩🇪 · Karl Jansen🇩🇪 · Kei-ichi Nagai🇩🇪 · Beatrix Pollakowski🇩🇪
We test the scaling behaviour of Wilson, hypercube, maximally twisted mass and overlap fermion actions in dynamical simulations of the 2-dimensional massive Schwinger model. We also present possibilities to simulate overlap fermions dynamically by replacing the exact overlap operator by an approximate version. This approximation is used either as only the guidance Hamiltonian, keeping the exact overlap operator as the accept/reject Hamiltonian or for both, the guidance and accept/reject Hamiltonian in the Hybrid Monte Carlo algorithm. In the latter case we test whether the approximation error can be corrected for by computing the determinant ratio of the exact and the approximate overlap operators stochastically.
hep-latPoS(2006)·6 citations
06*
Mass Spectra of Pentaquarks -- Overlap versus Wilson Fermions
Ting-Wai Chiu🇹🇼 · Tung-Han Hsieh🇹🇼
We investigate the mass spectra of $Θ^{+} (u d u d s ˉ)$ in quenched lattice QCD, with overlap and Wilson fermions respectively. Using three different interpolating operators, we measure their correlation matrix, and extract the mass spectra in even and odd parity channels, for 100 gauge configurations generated with single plaquette action at $β = 6.1$ on the $2 0^{3} \times 40$ lattice. The lowest $1/ 2^{-}$ state agrees with the $K N$ s-wave scattering state, for both fermion schemes. On the other hand, for the lowest $1/ 2^{+}$ state, it is different from any hadron scattering states for the overlap fermion, while it seems to agree with $K N^{*}$ s-wave for the Wilson fermion.
hep-lathep-exhep-phPoS(2006)·3 citations
07*
The locality of the fourth root of staggered fermion determinant in the interacting case
C. Bernard (1)🇺🇸 · C. DeTar (2)🇺🇸 · Steven Gottlieb (3)🇺🇸 · U. Heller (4)🇺🇸 · J.E. Hetrick (5)🇺🇸 · L. Levkova (3)🇺🇸 · F. Maresca (2)🇺🇸 · D. Renner (6)🇺🇸 · R. Sugar (7)🇺🇸 · D. Toussaint (6) ((1) Wash. U., (2) U. Utah., (3) Indiana U., (4) APS, (5) U. Pacific, (6) U. Arizona, (7) UCSB)
The fourth root approximation in LQCD simulations with dynamical staggered fermions requires justification. We test its validity numerically in the interacting theory in a renormalization group framework.
hep-latPoS(2006)·20 citations
08*
The Index Theorem and Random Matrix Theory for Improved Staggered Quarks
E. Follana🇬🇧 · A. Hart🇬🇧 · C.T.H. Davies🇬🇧
We study various improved staggered quark Dirac operators on quenched gluon backgrounds in lattice QCD. We find a clear separation of the spectrum of eigenvalues into high chirality, would-be zero modes and others, in accordance with the Index Theorem. We find the expected clustering of the non-zero modes into quartets as we approach the continuum limit. The predictions of random matrix theory for the epsilon regime are well reproduced. We conclude that improved staggered quarks near the continuum limit respond correctly to QCD topology.
hep-latPoS(2006)·4 citations
09*
Probing the chiral limit of M_pi and f_pi in 2+1 flavor QCD with domain wall fermions from QCDOC
Meifeng Lin (RBC and UKQCD Collaborations)🇺🇸
We present results for the pseudoscalar meson masses and decay constants on 2+1 flavor DWF configurations with different sea quark masses and an inverse lattice spacing of 1.6(1) GeV, with a focus on chiral fits at small quark masses. The calculation is done on 16^3x32x8 lattices generated with the DBW2 gauge action.
hep-latPoS(2006)·6 citations
10*
Combining Quark and Link Smearing to Improve Extended Baryon Operators
Adam Lichtl🇺🇸 · Subhasish Basak🇺🇸 · Robert Edwards🇺🇸 · George T. Fleming🇺🇸 · Urs M. Heller🇺🇸 · Colin Morningstar🇺🇸 · David Richards🇺🇸 · Ikuro Sato🇺🇸 · Stephen Wallace🇺🇸
The effects of Gaussian quark-field smearing and analytic stout-link smearing on the correlations of gauge-invariant extended baryon operators are studied. Gaussian quark-field smearing substantially reduces contributions from the short wavelength modes of the theory, while stout-link smearing significantly reduces the noise from the stochastic evaluations. The use of gauge-link smearing is shown to be crucial for baryon operators constructed of covariantly-displaced quark fields. Preferred smearing parameters are determined for a lattice spacing a_s ~ 0.1 fm.
hep-latPoS(2006)·30 citations
11*
Lattice QCD at Finite Temperature and Density
M.P. Lombardo🇮🇹
A general introduction into the subject aimed at a general theoretical physics audience. We introduce the sign problem posed by finite density lattice QCD, and we discuss the main methods proposed to circumvent it, with emphasis on the imaginary chemical potential approach. The interrelation between the Taylor expansion and the analytic continuation from imaginary chemical potential is discussed in detail. The main applications to the calculation of the critical line, and to the thermodynamics of the hot and the hadronic phase are reviewed.
hep-latMod.Phys.Lett.A(2007)·12 citations
12*
On the regularization ambiguities in loop quantum gravity
Alejandro Perez🇫🇷
One of the main achievements of LQG is the consistent quantization of the Wheeler-DeWitt equation which is free of UV problems. However, ambiguities associated to the intermediate regularization procedure lead to an apparently infinite set of possible theories. The absence of an UV problem is intimately linked with the ambiguities arising in the quantum theory. Among these ambiguities there is the one associated to the SU(2) unitary rep. used in the diffeomorphism covariant pointsplitting regularization of nonlinear funct. of the connection. This ambiguity is labelled by a halfinteger m and, here, it is referred to as the m-ambiguity. The aim of this paper is to investigate the important implications of this ambiguity./ We first study 2+1 gravity quantized in canonical LQG. Only when the regularization of the quantum constraints is performed in terms of the fundamental rep. of the gauge group one obtains the usual TQFT. In all other cases unphysical local degrees of freedom arise at the level of the regulated theory that conspire against the existence of the continuum limit. This shows that there is a clear cut choice in the quantization of the constraints in 2+1 LQG./ We then analyze the effects of the ambiguity in 3+1 gravity exhibiting the existence of spurious solutions for higher unit. rep. quantizations of the Hamiltonian constraint. Although the analysis is not complete in D=3+1--due to the difficulties associated to the definition of the physical inner product--it provides evidence supporting the definitions quantum dynamics of loop quantum gravity in terms of the fundamental representation of the gauge group as the only consistent possibilities. If the gauge group is SO(3) we find physical solutions associated to spin-two local excitations.
↳ gr-qchep-lathep-thPRD(2006)·101 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.