1,717 research outputs found

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

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    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

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    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

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    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)m(L) in the non--linear σ\sigma--model. No cut--off effect of the type g4(a/L)ng^4\left(a/L\right)^n is seen for any nn. 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

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    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

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

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    In this paper (the second of a series) we extend our calculation of a classical fixed point action for lattice SU(3)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=Lσ(L)G = L \sqrt{\sigma(L)} where the string tension σ(L)\sigma(L) is measured from the torelon mass μ=Lσ(L)\mu = L \sigma(L). We measure GG on lattices of fixed physical volume and varying lattice spacing aa (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 1/2aTc1/6 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

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    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 S1/2S \geq 1/2. With two independent quantum Monte Carlo algorithms and a finite-size-scaling technique, we explore correlation lengths up to ξ105\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 ξ/a=O(100)\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