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arXiv 1108.5697astro-ph.COgr-qc
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早期粘性宇宙中的夸克-强子相变

Quark-Hadron Phase Transitions in Viscous Early Universe

A. Tawfik, T. Harko

备注：
27 pages, 17 figures, revtex style (To appear in Phys. Rev. D). arXiv admin note: text overlap with arXiv:gr-qc/0404045
发表信息：
Phys. Rev. D 85, 084032 (2012)
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摘要：

基于热大爆炸理论，我们假设宇宙在$1-10 μ$ s年龄时，宇宙物质经历了QCD相变。在本工作中，我们考虑了体粘滞效应，研究了夸克-强子相变。我们分析了早期宇宙的物理描述，即能量密度$ρ$，温度$T$，哈勃参数$H$和比例因子$a$相变之前，期间和之后的相关量的演变。为了研究宇宙动力学和时间演化，我们使用解析和数值方法。通过假设相变可以描述的有效成核理论（提示{\it一阶}相变），我们也考虑的情况下，宇宙通过一个小的初始过冷和单调增长的强子气泡的混合相演变。例如，对宇宙学参数$a$和$H$的数值估计清楚地表明，时间演化随相位而变化。随着量子色动力学时代在高能实验和格点量子色动力学模拟中的逐渐接近，量子色动力学状态方程得到了很好的定义。基于此，我们系统地研究了{\it cross-over}夸克-强子相变，并对哈勃参数的时间演化进行了估计。

英文摘要：

Based on hot big bang theory, the cosmological matter is conjectured to undergo QCD phase transition(s) to hadrons, when the universe was about $1-10 μ$s old. In the present work, we study the quark-hadron phase transition, by taking into account the effect of the bulk viscosity. We analyze the evolution of the quantities relevant for the physical description of the early universe, namely, the energy density $ρ$, temperature $T$, Hubble parameter $H$ and scale factor $a$ before, during and after the phase transition. To study the cosmological dynamics and the time evolution we use both analytical and numerical methods. By assuming that the phase transition may be described by an effective nucleation theory (prompt {\it first-order} phase transition), we also consider the case where the universe evolved through a mixed phase with a small initial supercooling and monotonically growing hadronic bubbles. The numerical estimation of the cosmological parameters, $a$ and $H$ for instance, makes it clear that the time evolution varies from phase to phase. As the QCD era turns to be fairly accessible in the high-energy experiments and the lattice QCD simulations, the QCD equation of state is very well defined. In light of this, we introduce a systematic study of the {\it cross-over} quark-hadron phase transition and an estimation for the time evolution of Hubble parameter.

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