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arXiv 1201.0445hep-ph
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QCD解围相界的临界点

Critical Point on the QCD Deconfining Phase Boundary

P. K. Srivastava, C. P. Singh

摘要:

关于QCD相界上的物理性质和临界点(CP)的存在仍然存在着歧义,而关于QCD相界的模糊性还没有澄清。在本文中,我们扩展了我们以前的研究,我们建立了一个退凝相边界后,使用准粒子状态方程(EOS)的夸克-胶子等离子体(QGP)和一个排除体积状态方程的强子气体(HG)的吉布斯平衡条件,并发现存在一个临界点的一级相变终止在这个相边界。在本文中,我们绘制了HG和QGP相之间的归一化熵密度($s/T^{3}$)的差异沿退细化相边界,并发现它消失在CP。进一步,我们分别给出了HG和QGP的声速平方($c_{s}^{2}$)的变化,发现它们之间的差($Δc_{s}^{2}$)沿退细化相界在边界CP处又消失了。在不同的重子化学势($μ_{B}$)下,我们还分别绘制了HG相和QGP相的剪切粘滞熵密度比($η/s$)随温度的变化曲线。在$η/s$中尖点状结构的存在再次证实了某些作者所预测的在去澄清相界上CP的存在。因此,这些研究坚定地表明CP作为二阶相变点的精确位置。

英文摘要:

Ambiguities regarding the physics and the existence of the critical point (CP) on the QCD phase boundary still exist and the mist regarding the conjectured QCD phase boundary has not yet cleared. In this paper we extend our earlier study where we constructed a deconfining phase boundary using Gibbs' equilibrium conditions after using a quasiparticle equation of state (EOS) for quark gluon plasma (QGP) and an excluded volume EOS for the hadron gas (HG) and find the presence of a critical point on this phase boundary where the first order phase transition terminates. In this paper, we plot the difference in the normalized entropy density ($s/T^{3}$) between HG and QGP phases along the deconfining phase boundary and find that it vanishes at CP. Further we have shown the variation of the square of speed of sound ($c_{s}^{2}$) for the HG and QGP separately and find that the difference ($Δc_{s}^{2}$) between them along the deconfining phase boundary again vanishes at the CP of the boundary. We also plot the variation of shear viscosity to entropy density ratio ($η/s$) in HG as well as in QGP phases separately with respect to temperature at different baryonic chemical potential ($μ_{B}$). The presence of a cusp like structure in $η/s$ again confirms the existence of CP on the deconfining phase boundary as predicted by some authors. These studies thus firmly indicate the precise location of CP as a second order phase transition point.

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