arXiv subjects

E. B. Gregory

Publications and source records attributed to E. B. Gregory.

27 records · Page 2Linked to original sources

arXiv2003

Pion and kaon physics with improved staggered quarks

We compute pseudoscalar meson masses and decay constants using staggered quarks on lattices with three flavors of sea quarks and lattice spacings $\approx 0.12$ fm and $\approx 0.09$ fm. We fit partially quenched results to ``staggered chiral perturbation theory'' formulae, thereby taking into account the effects of taste-symmetry violations. Chiral logarithms are observed. From the fits we calculate $f_π$ and $f_K$, extract Gasser-Leutwyler parameters of the chiral Lagrangian, and (modulo rather large perturbative errors) find the light and strange quark masses.

hep-lat↗

arXiv2003

High-Precision Lattice QCD Confronts Experiment

We argue that high-precision lattice QCD is now possible, for the first time, because of a new improved staggered quark discretization. We compare a wide variety of nonperturbative calculations in QCD with experiment, and find agreement to within statistical and systematic errors of 3% or less. We also present a new determination of alpha_msbar(Mz); we obtain 0.121(3). We discuss the implications of this breakthrough for phenomenology and, in particular, for heavy-quark physics.

hep-lat↗

arXiv2002

Exotic hybrid mesons from improved Kogut-Susskind fermions

We summarize our measurement of the mass of the exotic $1^{-+}$ hybrid meson using an improved Kogut-Susskind action. We show results from both quenched and dynamical quark simulations and compare with results from Wilson quarks. Extrapolation of these results to the physical quark mass allows comparison with experimental candidates for the $1^{-+}$ hybrid meson.

hep-lat↗

arXiv2002

Light hadron properties with improved staggered quarks

Preliminary results from simulations with 2+1 dynamical quark flavors at a lattice spacing of 0.09 fm are combined with earlier results at a=0.13 fm. We examine the approach to the continuum limit and investigate the dependence of the pseudoscalar masses and decay constants as the sea and valence quark masses are separately varied.

hep-lat↗

arXiv2002

Light Hadron Masses in QCD with Valence Wilson Quarks at beta=6.25 from a Parallel PC Cluster

We present results for $π$, $ρ$ and proton and $Δ$ masses from our recently built Pentium cluster. The previous results for quenched Wilson fermions by MILC and GF11 collaborations are compared at $β=6/g^2$=5.7 and 5.85 with the same parameters on the $8^3\times32$ lattice. New data are shown at $β$=6.25 on the $12^3\times36$ and $16^3\times32$ lattices. Such a larger $β$ value is useful for extrapolating the lattice results to the continuum limit. The smearing technique is systematically investigated and shown to greatly improve the spectrum data.

hep-lat↗

arXiv2001

Parallel Computing on a PC Cluster

The tremendous advance in computer technology in the past decade has made it possible to achieve the performance of a supercomputer on a very small budget. We have built a multi-CPU cluster of Pentium PC capable of parallel computations using the Message Passing Interface (MPI). We will discuss the configuration, performance, and application of the cluster to our work in physics.

cs.DC↗

arXiv2000

Parallel Computing for QCD on a Pentium Cluster

Motivated by the computational demands of our research and budgetary constraints which are common to many research institutions, we built a ``poor man's supercomputer'', a cluster of PC nodes which together can perform parallel calculations at a fraction of the price of a commercial supercomputer. We describe the construction, cost, and performance of our cluster.

hep-lat↗

arXiv2000

Hamiltonian lattice QCD at finite chemical potential

At sufficiently high temperature and density, quantum chromodynamics (QCD) is expected to undergo a phase transition from the confined phase to the quark-gluon plasma phase. In the Lagrangian lattice formulation the Monte Carlo method works well for QCD at finite temperature, however, it breaks down at finite chemical potential. We develop a Hamiltonian approach to lattice QCD at finite chemical potential and solve it in the case of free quarks and in the strong coupling limit. At zero temperature, we calculate the vacuum energy, chiral condensate, quark number density and its susceptibility, as well as mass of the pseudoscalar, vector mesons and nucleon. We find that the chiral phase transition is of first order, and the critical chemical potential is $μ_C =m_{dyn}^{(0)}$ (dynamical quark mass at $μ=0$). This is consistent with $μ_C \approx M_N^{(0)}/3$ (where $M_N^{(0)}$ is the nucleon mass at $μ=0$).

hep-lat↗

arXiv1998

The Renormalization Group and its Finite Lattice Approximations

We investigate finite lattice approximations to the Wilson Renormalization Group in models of unconstrained spins. We discuss first the properties of the Renormalization Group Transformation (RGT) that control the accuracy of this type of approximations and explain different methods and techniques to practically identify them. We also discuss how to determine the anomalous dimension of the field. We apply our considerations to a linear sigma model in two dimensions in the domain of attraction of the Ising Fixed Point using a Bell-Wilson RGT. We are able to identify optimal RGTs which allow accurate computations of quantities such as critical exponents, fixed point couplings and eigenvectors with modest statistics. We finally discuss the advantages and limitations of this type of approach.

cond-mat.stat-mech↗