标题： 带奇异夸克的QCD在有限温度下的相变：用格点上的威尔逊费米子进行研究 显示英文标题

标题： FINITE TEMPERATURE PHASE TRANSITION IN QCD WITH STRANGE QUARK: STUDY WITH WILSON FERMIONS ON THE LATTICE

摘要： 奇异夸克在QCD有限温度相变中的影响是在格点上研究的。 使用单元格规范作用量和威尔逊夸克作用量，显示在手征极限下，对于简并的两种味道的情况，$N_F=2$，相变是连续的，而对于$N_F \geq 3$则是第一类的。 对于更现实的情况，即无质量的上夸克和下夸克以及轻的奇异夸克，$N_F=2+1$，在$m_s \simeq 150$和400 MeV时都观察到了明显的两态信号。 与之前使用交错夸克的结果相反，这表明在现实世界中存在第一类相变。 为了了解这些结果对连续极限的影响，我们开始使用改进的作用量来研究这些问题。 首先给出了使用RG改进的规范作用量结合标准威尔逊夸克作用量的情况$N_F=2$的第一批结果：通过这种作用量，在手征极限下有限温度相变被证明是连续的，确认了标准作用量的结果。 此外，与标准作用量的情况不同，在标准作用量中，格点效应使得在跳跃参数 $K$ 的中间值时转变非常强烈，出现在 $N_t=4$ 和 6 格点上，当我们将 $1/K-1/K_c$ 增加时，改进的作用量发现了一个平滑的交叉，这与对有限 $m_q$ 下二阶手征转变命运的直观预期一致。 显示英文摘要

摘要： The effect of the strange quark in the finite temperature phase transition of QCD is studied on the lattice. Using the one-plaquette gauge action and the Wilson quark action, the transition in the chiral limit is shown to be continuous for the case of degenerate two flavors, $N_F=2$, while it is of first order for $N_F \geq 3$. For a more realistic case of massless up and down quarks and a light strange quark, $N_F=2+1$, clear two state signals are observed both for $m_s \simeq 150$ and 400 MeV. In contrast to a previous result with staggered quarks, this suggests a first order transition in the real world. In order to see the implication of these results to the continuum limit, we started to study these issues using improved actions. First results using a RG improved gauge action combined with the standard Wilson quark is presented for the case of $N_F=2$: With this action the finite temperature transition is shown to be continuous in the chiral limit confirming the result of the standard action. Furthermore, not like the case of the standard action where lattice artifacts make the transition once very strong at intermediate values of the hopping parameter $K$ on $N_t=4$ and 6 lattices, a smooth crossover is found for the improved action when we increase $1/K-1/K_c$, in accord with a naive expectation about the fate of second order chiral transition at finite $m_q$.