Improving the Partial-Global Stochastic Metropolis Update for Dynamical Smeared Link Fermions

We discuss several methods that improve the partial-global stochastic Metropolis (PGSM) algorithm for smeared link staggered fermions. We present autocorrelation time measurements and argue that this update is feasible even on reasonably large lattices.Comment: 3 pages, 3 figures, Lattice2002(algor

The role of heavy fermions

Heavy dynamical fermions with masses around the cut-off do not change the low energy physics apart from a finite renormalization of the gauge coupling. In this paper we study how light the heavy fermions have to be to cause more than this trivial renormalization.Comment: uuencoded 3 page postscript contribution to Lattice 93, COLO-HEP-33

The absence of cut--off effects for the fixed point action in 1--loop perturbation theory

In order to support the formal renormalization group arguments that the fixed point action of an asymptotically free model gives cut--off independent physical predictions in 1--loop perturbation theory, we calculate the finite volume mass--gap $m(L)$ in the non--linear $\sigma$--model. No cut--off effect of the type $g^4\left(a/L\right)^n$ is seen for any $n$. The results are compared with those of the standard and tree level improved Symanzik actions.Comment: 8 pages (latex) + 1 figure (Postscript), uuencode

Using Approximating Polynomials in Partial-Global Dynamical Simulations

Smeared link fermionic actions can be straightforwardly simulated with partial-global updating. The efficiency of this simulation is greatly increased if the fermionic matrix is written as a product of several near-identical terms. Such a break-up can be achieved using polynomial approximations for the fermionic matrix. In this paper we will focus on methods of determining the optimum polynomials.Comment: 3 pages, 3 figures, Lattice2002(algor

Dynamical Simulations with Smeared Link Staggered Fermions

One of the most serious problems of the staggered fermion lattice action is flavor symmetry violation. Smeared link staggered fermions can improve flavor symmetry by an order of magnitude relative to the standard thin link action. Over the last few years different smearing transformations have been proposed, both with perturbatively and non-perturbatively determined coefficients. What hindered the acceptance and more general use of smeared link fermions until now is the relative difficulty of dynamical simulations and the lack of perturbative calculations with these actions. In both areas there have been significant improvement lately, that I will review in this paper.Comment: 9 pages,5 figures; Plenary talk contribution to Lattice'200

An Effective Action for Finite Temperature QCD with Fermions

Using lattice perturbation theory at finite temperature, we compute for staggered fermions the one-loop fermionic corrections to the spatial and temporal plaquette couplings as well as the leading $Z_N$ symmetry breaking coupling. Numerical and analytical considerations indicate that the finite temperature corrections to the zero-temperature calculation of A. Hasenfratz and T. DeGrand are small for small values of $\kappa = {1\over 2m_F}$, but become significant for intermediate values of $\kappa$. The effect of these finite temperature corrections is to ruin the agreement of the Hasenfratz-DeGrand calculation with Monte Carlo data. We conjecture that the finite temperature corrections are suppressed nonperturbatively at low temperatures, resolving this apparent disagreement. The $Z_N$ symmetry breaking coupling is small; we argue that it may change the order of the transition while having little effect on the critical value of $\beta$.Comment: 3 pages, 3 figures, latex, self-extracting, Lattice '94 contributio

Towards a perfect fixed point action for SU(3) gauge theory

We present an overview of the construction and testing of actions for SU(3) gauge theory which are approximate fixed points of renormalization group equations (at $\beta\rightarrow \infty$). Such actions are candidates for use in numerical simulations on coarse lattices.Comment: 6 pages, uuencoded compressed postscript file, contribution to LAT9

Fermion induced SU(N)(N) Yang-Mills Theory

We investigate the gauge interaction induced by heavy fermions using both dimensional and lattice regularization. We study the condition under which heavy fermions induce a continuum gauge theory.Comment: 4 pages; talk at Lattice '92, Amsterdam, requires , espcrc2.st

Non--perturbative tests of the fixed point action for SU(3) gauge theory

In this paper (the second of a series) we extend our calculation of a classical fixed point action for lattice $SU(3)$ pure gauge theory to include gauge configurations with large fluctuations. The action is parameterized in terms of closed loops of link variables. We construct a few-parameter approximation to the classical FP action which is valid for short correlation lengths. We perform a scaling test of the action by computing the quantity $G = L \sqrt{\sigma(L)}$ where the string tension $\sigma(L)$ is measured from the torelon mass $\mu = L \sigma(L)$. We measure $G$ on lattices of fixed physical volume and varying lattice spacing $a$ (which we define through the deconfinement temperature). While the Wilson action shows scaling violations of about ten per cent, the approximate fixed point action scales within the statistical errors for $1/2 \ge aT_c \ge 1/6$. Similar behaviour is found for the potential measured in a fixed physical volume.Comment: 28 pages (latex) + 11 figures (Postscript), uuencode

Reconciling the correlation length for high-spin Heisenberg antiferromagnets

We present numerical results for the antiferromagnetic Heisenberg model (AFHM) that definitively confirm that chiral perturbation theory, corrected for cutoff effects in the AFHM, leads to a correct field-theoretical description of the low-temperature behavior of the spin correlation length for spins $S \geq 1/2$. With two independent quantum Monte Carlo algorithms and a finite-size-scaling technique, we explore correlation lengths up to $\xi \approx 10^5$ lattice spacings a for spins S=1 and 5/2. We show how the recent prediction of cutoff effects by P. Hasenfratz is approached for moderate $\xi/a={\cal O}(100)$, and smoothly connects with other approaches to modeling the AFHM at smaller correlation lengths.Comment: 4 pages plus 3 EPS figures, submitted to PR