1,717 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 $m(L)$ 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

### 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

- â€¦