谱函数的一种变分方法
A variational method for spectral functions
摘要：
为了从格点量子色动力学中计算的含时欧几里德算符中可靠地提取能级，广义本征值问题（GEVP）在过去被广泛地应用。我们提出了一个公式的GEVP在频率空间。我们的方法包括应用模型无关的巴科斯-吉尔伯特方法的一组欧几里得两点函数与共同的量子数。然后，将频率空间中的GEVP分析应用于估计量矩阵，该估计量矩阵允许我们获得初始操作符集合的特定线性组合，该初始操作符集合最佳地重叠到频率中的不同局部区域。我们应用这种方法从NRQCD格点数据。这种方法对真空物理和有限温度问题都很有意义。
英文摘要：
The Generalized Eigenvalue Problem (GEVP) has been used extensively in the past in order to reliably extract energy levels from time-dependent Euclidean correlators calculated in Lattice QCD. We propose a formulation of the GEVP in frequency space. Our approach consists of applying the model-independent Backus-Gilbert method to a set of Euclidean two-point functions with common quantum numbers. A GEVP analysis in frequency space is then applied to a matrix of estimators that allows us, among other things, to obtain particular linear combinations of the initial set of operators that optimally overlap to different local regions in frequency. We apply this method to lattice data from NRQCD. This approach can be interesting both for vacuum physics as well as for finite-temperature problems.
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