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标题：The curvature of the critical surface (m_ud,m_s)^{crit}(mu): a progress report
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作者：P. de-Forcrand
期刊名称：PoS - Proceedings of Science
印刷版ISSN：1824-8039
出版年度：2008
卷号：2008
出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：At zero chemical potential m, the order of the temperature-driven quark-hadron transition depends on the quark masses mu,d and ms. Along a critical line bounding the region of first-order chiral transitions in the (mu,d,ms) plane, this transition is second order. When the chemical potential is turned on, this critical line spans a surface, whose curvature at m = 0 can be determined without any sign or overlap problem. Our past measurements on Nt = 4 lattices suggest that the region of quark masses for which the transition is first order shrinks when m is turned on, which makes a QCD chiral critical point at small m/T unlikely. We present results from two complementary methods, which can be combined to yield information on higher-order terms. It turns out that the O(m4) term reinforces the effect of the leading O(m2) term, and there is strong evidence that the O(m6) and O(m8) terms do as well. We also report on simulations underway, where the strange quark is given its physical mass, and where the lattice spacing is reduced.