2,159 research outputs found
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 in the non--linear --model. No cut--off effect
of the type is seen for any . 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 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 , but
become significant for intermediate values of . 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 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 .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 ). 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 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 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 where the string tension is measured from the
torelon mass . We measure on lattices of fixed physical
volume and varying lattice spacing (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 . 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 . With two independent quantum Monte Carlo algorithms and a
finite-size-scaling technique, we explore correlation lengths up to 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
, and smoothly connects with other approaches to modeling
the AFHM at smaller correlation lengths.Comment: 4 pages plus 3 EPS figures, submitted to PR
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