NUMERICAL STUDY OF LATTICE QCD WITH THREE DYNAMICAL QUARKS

三动态夸克晶格QCD的数值研究

基本信息

批准号：
13640259
负责人：
UKAWA Akira
金额：
$ 1.79万
依托单位：
UNIVERSITY OF TSUKUBA
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-13640259/
关键词：
LATTICE GAUGE THEORY LATTICE QCD NUMERICAL SIMULATIONS QUARK PHASE TRANSITION CLOVER ACTION MONTE CARLO METHOD PERTURBATIVE EXPANSION

项目摘要

This work aimed to develop methods for lattice QCD simulations including dynamical strange quark in addition to dynamical up and down quarks. The main results we have obtained are as follows.1. Algorithm developmentTreating odd number of dynamical quarks requires an algorithmic development. We have shown that the polynomial HMC, in which the inverse of a single Dirac operator needed for the strange quark is approximated by a polynomial, provides a viable method for this purpose. We have also extended the algorithm to the Kogut-Susskind action, and has formulated an exact PHMC algorithm for it; such an exact algorithm had not been known before.2. phase structure of three-flavor lattice QCDWe have applied the algorithm to study the phase structure for three-flavor lattice QCD at finite lattice spacings. It was found that the combination of the plaquette and clover quark action develops a line of first-order phase transition which is a lattice artifact. While the transition terminates bef … More ore reaching the continuum limit, the lattice spacing at the termination point turned out to be about 4GeV. Since we need to start simulations closer to the continuum limit to avoid unphysical effects of such phase transitions, the plaquette-clover combination appears impractical for carrying out actual simulations. Switching the gauge action to an RG-improved action, it was found that the phase transition disappears, presumably because gauge field fluctuation becomes more continuum-like for improved actions.3. Determination of the clover coefficient for RG-improved gauge actionTo carry out a continuum extrapolation using lattice spacing 1/a=1-2GeV, an O (a) improved action is needed. Since the clover coefficient for the RG-improved gauge action is not known, we have decided to apply the Schrodinger functional method for this purpose. It turned out that O(a/L) errors need to be controlled precisely for this purpose, since bare gauge coupling is large. We treated this problem through simulations with a fixed L(in physical units), and determined the clover coefficient as a function of the bare gauge coupling.4. Physics runsAs a first step toward realistic three flavor QCD simulations, we have started runs at l/a=2GeV using 16^3x32 lattices. We plan to carry out the light hadron spectrum run, followed by determinations of light quark masses and the QCD coupling constant. Further work on heavy quark physics shall utilize gauge configurations generated in those studies. Less

这项工作旨在开发除动态上夸克和下夸克之外的晶格 QCD 模拟方法。我们获得的主要结果如下： 1. 处理奇数个动态夸克需要算法开发。多项式 HMC（其中奇异夸克所需的单个狄拉克算子的逆是用多项式近似的）为此目的提供了一种可行的方法，我们还扩展了算法对Kogut-Susskind作用，并为其制定了一种精确的PHMC算法；这种精确的算法是以前未知的。2．三味格子QCD的相结构我们应用该算法来研究三味格子的相结构。有限晶格间距下的味晶格 QCD 发现，斑块和三叶草夸克作用的结合产生了一条一级相变线，这是一种晶格伪影。相变在达到连续体极限之前终止，终点处的晶格间距约为 4GeV，因为我们需要在接近连续体极限的地方开始模拟，以避免此类相变的非物理效应，即“板状三叶草”。组合对于进行实际模拟似乎不切实际，将规范动作切换为 RG 改进的动作，发现相变消失，大概是因为规范场波动变得更大。 3.确定RG改进规范作用的三叶草系数为了使用晶格间距1/a=1-2GeV进行连续统外推，需要O(a)改进的作用，因为三叶草系数。由于 RG 改进的规范作用未知，我们决定为此应用薛定谔泛函方法，事实证明需要控制 O(a/L) 误差。正是出于这个目的，因为裸规范耦合很大，我们通过使用固定 L（以物理单位表示）的模拟来处理这个问题，并确定三叶草系数作为裸规范耦合的函数。4。现实的三味 QCD 模拟，我们已经开始使用 16^3x32 晶格在 l/a=2GeV 下运行，我们计划进行轻强子谱运行，然后确定轻夸克质量和 QCD 耦合常数。关于重夸克物理的研究应利用这些研究中产生的规范配置。