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arXiv 0803.1092hep-lat
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SU(N)格点规范理论中裸耦合的运行

On the running of the bare coupling in SU(N) lattice gauge theories

Chris Allton, Michael Teper, Aurora Trivini

摘要:

解释SU(3)裸格点耦合随格点间距变化的方式是复杂的,因为存在一个光滑的交叉区域,在这个区域中强耦合展开转变为弱耦合展开。然而,对于N > 4,存在一级体跃迁,其清楚地分离强耦合和弱耦合区域。我们发现,在这种情况下,计算出的弦张力可以很容易地安装在整个弱耦合区域由一个标准的3圈表达式修改晶格间距修正的预期形式。虽然我们的拟合要求后者的存在,但它们不足以约束微扰耦合方案,使我们能够以Lambda_MSbar为单位提取有用的准确值。为了解决这种模糊性,我们转向SU(3),其中我们使用薛定谔泛函耦合方案来提取r_0 x Lambda_SF的值作为基准。然后,我们发现,Parisi平均场改进的耦合方案密切再现这一结果。我们还开发了不同的方案之间的比较,不依赖于任何物理量的计算,因此可以进一步应用到弱耦合。同样,Parisi方案优于我们比较的其他方案。利用平均场方法,我们拟合了在N=2 ~ N=8的情况下计算出的弦张力值,得到λ_MSbar/sqrt(sigma)= 0.503(2)(40)+ 0.33(3)(3)/N^2(N > 2),其中第一个误差是统计误差,第二个误差是我们对所有来源的系统误差的估计。

英文摘要:

Interpreting the way that the SU(3) bare lattice coupling runs with the lattice spacing is complicated by the fact that there is a smooth cross-over region in which the strong coupling expansion transforms into a weak-coupling one. For N > 4, however, there is a first order bulk transition that cleanly separates the strong and weak coupling regimes. We find that in this case the calculated string tension can be readily fitted throughout the weak coupling region by a standard 3-loop expression modified by lattice spacing corrections of the expected form. While our fits demand the presence of the latter, they do not constrain the perturbative coupling scheme enough to enable us to extract a usefully accurate value of a(beta) in units of Lambda_MSbar. To resolve this ambiguity we turn to SU(3) where we use the Schrodinger Functional coupling scheme to extract a value of r_0 x Lambda_SF as a benchmark. We then find that the Parisi mean-field improved coupling scheme closely reproduces this result. We also develop a comparison between different schemes that does not rely on the calculation of any physical quantity and which can therefore be applied much further into weak coupling. Again the Parisi scheme is favoured over the others that we compare. Using the mean-field scheme we have fitted the values of the string tension that have been calculated for N=2 to N=8, to obtain Lambda_MSbar/sqrt(sigma) = 0.503(2)(40) + 0.33(3)(3)/N^2 for N > 2, where the first error is statistical and the second is our estimate of the systematic error from all sources.

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