Domain-Wall Fermions at Strong Coupling

The DWF formulation becomes increasingly problematic at gauge couplings for which $a^{-1}<2$ GeV, where the roughness of the gauge field leads to increased explicit chiral symmetry breaking (\mres). This problem becomes especially severe for sufficiently strong coupling where the underlying 4-dimensional Wilson theory is in the Aoki phase. We review our attempts to find a suitable modification of the gauge and/or the fermion action which would allow the DWF method to work reliably at stronger coupling.Comment: 4 pages, 4 figures, Lattice2004(chiral

Staggered Fermion Thermodynamics using Anisotropic Lattices

Numerical simulations of full QCD on anisotropic lattices provide a convenient way to study QCD thermodynamics with fixed physics scales and reduced lattice spacing errors. We report results from calculations with 2-flavors of dynamical fermions where all bare parameters and hence the physics scales are kept constant while the temperature is changed in small steps by varying only the number of the time slices. The results from a series of zero-temperature scale setting simulations are used to determine the Karsch coefficients and the equation of state at finite temperatures.Comment: Lattice2002(nonzerot), 3 pages, 2 figure

Improving Dynamical Domain-Wall Fermion Simulations

We report on studies of the chiral properties of dynamical domain wall fermions combined with the DBW2 gauge action for different gauge couplings and fermion masses. For quenched theories, the DBW2 action gives a residual chiral symmetry breaking much smaller than what was found with more traditional choices for the gauge action. Our goal is to investigate the possibilities which this and further improvements provide for the study of QCD thermodynamics and other simulations at stronger couplings.Comment: 3 pages, 4 figures, 3 tables, Lattice2003(improve

Anisotropic Lattices and Dynamical Fermions

We report results from full QCD calculations with two flavors of dynamical staggered fermions on anisotropic lattices. The physical anisotropy as determined from spatial and temporal masses, their corresponding dispersion relations, and spatial and temporal Wilson loops is studied as a function of the bare gauge anisotropy and the bare velocity of light appearing in the Dirac operator. The anisotropy dependence of staggered fermion flavor symmetry breaking is also examined. These results will then be applied to the study of 2-flavor QCD thermodynamics.Comment: Lattice2001(spectrum

QCD thermodynamics with nonzero chemical potential at Nt=6N_t=6 and effects from heavy quarks

We extend our work on QCD thermodynamics with 2+1 quark flavors at nonzero chemical potential to finer lattices with $N_t=6$. We study the equation of state and other thermodynamic quantities, such as quark number densities and susceptibilities, and compare them with our previous results at $N_t=4$. We also calculate the effects of the addition of the charm and bottom quarks on the equation of state at zero and nonzero chemical potential. These effects are important for cosmological studies of the early Universe.Comment: 27 pages, 17 figures. Some small text and figure change

Charmonium mass splittings at the physical point

We present results from an ongoing study of mass splittings of the lowest lying states in the charmonium system. We use clover valence charm quarks in the Fermilab interpretation, an improved staggered (asqtad) action for sea quarks, and the one-loop, tadpole-improved gauge action for gluons. This study includes five lattice spacings, 0.15, 0.12, 0.09, 0.06, and 0.045 fm, with two sets of degenerate up- and down-quark masses for most spacings. We use an enlarged set of interpolation operators and a variational analysis that permits study of various low-lying excited states. The masses of the sea quarks and charm valence quark are adjusted to their physical values. This large set of gauge configurations allows us to extrapolate results to the continuum physical point and test the methodology.Comment: 7 pp, 6 figs, Lattice 201