ar X iv : h ep - l at / 9 90 80 22 v 1 1 8 A ug 1 99 9 KANAZAWA 99 – 17 HUB - EP - 99 / 37
نویسنده
چکیده
Decorrelation of the topological charge in Hybrid Monte Carlo (HMC) simulations of QCD with dynamical fermions is a long standing problem. For staggered fermions an insufficient tunneling rate of the topological charge Qt has been observed [1,2]. For Wilson fermions the tunneling rate is adequate in many cases [3,4]. However on large lattices and for large values of κ near the chiral limit the distribution of Qt is not symmetric even after more than 3000 trajectories (see Figure 1 of [3] and similar observations by CP-PACS [5]). The idea of parallel tempering is to improve transitions in parameter regions where tunneling is suppressed by opening ways through parameter regions with little suppression. In QCD the method has been applied successfully for staggered fermions [6]. In [7] parallel tempering has been used to simulate QCD with O(a)-improved Wilson fermions without finding any gain, however, with only two ensembles which does not take advantage of the main idea of the method. Here we use parallel tempering in conjunction with HMC to simulate QCD with (standard) Wilson fermions in a parameter range close to the critical region, where the method is expected to be most advantageous. The gain achieved is demonstrated by studying time series and histograms of the topological charge.
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