arXiv 0910.07852009-10-05hep-ph

QCD手性临界表面的确定

Towards a determination of the chiral critical surface of QCD

Owe Philipsen

备注：: 8 pages, 6 figures; Invited talk given at CPOD 2009, June 8-12 2009, Brookhaven, NY
发表信息：: PoS CPOD2009:026,2009

摘要：

手征临界面是{ m_{u,d}，m_s，μ}参数空间中小质量夸克的一阶手征相变区域的边界。QCD（T，μ）-相图的潜在临界端点被广泛认为是这个表面的一部分。由于对于μ=0且具有物理夸克质量的QCD已知会表现出解析交叉，因此这种期望要求手征跃迁的区域随着μ而扩展，以使手征临界端点存在。相反，在N_t=4的粗晶格上，我们发现手征跃迁的面积随着μ的减小而减小，这就排除了在中等化学势μ_B < 500 MeV时QCD的手征临界点。在N_t=6的较细晶格上的初步结果表明临界曲面的曲率与零和不变的结论一致。我们还评述了N_f=2和N_f=2+1理论之间相图的相互作用及其对物理QCD的影响。

英文摘要：

The chiral critical surface is a surface of second order phase transitions bounding the region of first order chiral phase transitions for small quark masses in the {m_{u,d}, m_s,μ} parameter space. The potential critical endpoint of the QCD (T,μ)-phase diagram is widely expected to be part of this surface. Since for μ=0 with physical quark masses QCD is known to exhibit an analytic crossover, this expectation requires the region of chiral transitions to expand with μfor a chiral critical endpoint to exist. Instead, on coarse N_t=4 lattices, we find the area of chiral transitions to shrink with μ, which excludes a chiral critical point for QCD at moderate chemical potentials μ_B < 500 MeV. First results on finer N_t=6 lattices indicate a curvature of the critical surface consistent with zero and unchanged conclusions. We also comment on the interplay of phase diagrams between the N_f=2 and N_f=2+1 theories and its consequences for physical QCD.

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