标题： 在存在破缺的 Z_2 对称性情况下的连通两点函数的方差缩减估计量 显示英文标题

标题： A variance reduced estimator of the connected two-point function in the presence of a broken Z_2 symmetry

摘要： 交换或几何簇算法使我们能够在存在破缺的Z_2对称性的情况下定义连接两点函数的方差降低估计量。我们对改进的Blume-Capel模型进行了首次数值测试，在简单立方晶格上进行。我们对临界等温线、零外场下的低温相进行了模拟，并为了比较，也对高温相进行了模拟。对于连接的两点函数，可以得到显著的方差减少，使我们能够以高精度计算关联长度。基于这些结果，计算了各种描述三维伊辛模型普适类的普遍振幅比的估计值。 显示英文摘要

摘要： The exchange or geometric cluster algorithm allows us to define a variance reduced estimator of the connected two-point function in the presence of a broken Z_2-symmetry. We present first numerical tests for the improved Blume-Capel model on the simple cubic lattice. We perform simulations for the critical isotherm, the low temperature phase at vanishing external field and, for comparison, also the high temperature phase. For the connected two-point function a substantial reduction of the variance can be obtained, allowing us to compute the correlation length with high precision. Based on these results, estimates for various universal amplitude ratios that characterise the universality class of the three-dimensional Ising model are computed.