标题： 微扰理论与模拟在纯规范理论中 tadpole 改进因子的比较 显示英文标题

标题： Perturbation theory vs. simulation for tadpole improvement factors in pure gauge theories

摘要： 我们使用两环微扰理论和蒙特卡罗模拟，采用加速朗之万算法，计算了威尔逊和改进的SU(3)各向异性规范作用下的平均链接，在兰道规范中。 采用了扭曲边界条件，在所有四个晶格方向上的扭曲显著提高了（傅里叶加速的）对改进的格点兰道规范的收敛性。 观察到两环微扰理论即使在通常模拟的规范耦合区域也能非常准确地预测平均链接，因此可以用来消除对自洽泡顶改进因子的数值调整的需要。 从模拟中推断出一个三环微扰系数，发现其值较小。 我们表明有限尺寸效应很小，并同样论证了（格点）格里布夫副本和双狄拉克片的影响也很小。 显示英文摘要

摘要： We calculate the mean link in Landau gauge for Wilson and improved SU(3) anisotropic gauge actions, using two loop perturbation theory and Monte Carlo simulation employing an accelerated Langevin algorithm. Twisted boundary conditions are employed, with a twist in all four lattice directions considerably improving the (Fourier accelerated) convergence to an improved lattice Landau gauge. Two loop perturbation theory is seen to predict the mean link extremely well even into the region of commonly simulated gauge couplings and so can be used remove the need for numerical tuning of self-consistent tadpole improvement factors. A three loop perturbative coefficient is inferred from the simulations and is found to be small. We show that finite size effects are small and argue likewise for (lattice) Gribov copies and double Dirac sheets.