arXiv 0911.46472009-11hep-ph

由维里展开计算夸克-胶子等离子体的剪切粘度

Shear viscosity of the Quark-Gluon Plasma from a virial expansion

S. Mattiello, W. Cassing

备注：: Published in Eur. Phys. J. C, 7 pages, 2 figures, 3 table
发表信息：: Eur.Phys.J.C70:243-249,2010
DOI：: 10.1140/epjc/s10052-010-1459-3

摘要：

我们用维里展开方法计算了夸克-胶子等离子体（QGP）相中的剪切粘滞系数$η$，特别关注$η$与熵密度$s$的比值，即$η/s$。维里展开的方法使我们能够包括部分子之间的相互作用在解除限制的阶段，并评估单粒子配分函数的修正。在后一种方法中，我们从一个有效的相互作用开始，参数固定，以再现QCD的物理量，如能量和/或熵密度。我们还直接提取了有效偶联物$\ga_{\rm V}$用于$η$的测定。我们的数值计算结果给出了在临界温度$T_{\rm c}$下的比率$η/s\approx 0.097$，这非常接近于$1/(4π)$的理论界限。此外，对于温度$T\leq 1.8 T_{\rm c}$，比率$η/s$在RHIC的当前实验估计值$0.1-0.3$的范围内。当结合我们的结果$η/s$在解除相与那些从手征微扰理论或共振气体模型在受限相，我们观察到一个明显的最小值$η/s$接近的临界温度$T_{\rm c}$。

英文摘要：

We calculate the shear viscosity $η$ in the quark-gluon plasma (QGP) phase within a virial expansion approach with particular interest in the ratio of $η$ to the entropy density $s$, i.e. $η/s$. The virial expansion approach allows us to include the interactions between the partons in the deconfined phase and to evaluate the corrections to a single-particle partition function. In the latter approach we start with an effective interaction with parameters fixed to reproduce thermodynamical quantities of QCD such as energy and/or entropy density. We also directly extract the effective coupling $\ga_{\rm V}$ for the determination of $η$. Our numerical results give a ratio $η/s\approx 0.097$ at the critical temperature $T_{\rm c}$, which is very close to the theoretical bound of $1/(4π)$. Furthermore, for temperatures $T\leq 1.8 T_{\rm c}$ the ratio $η/s$ is in the range of the present experimental estimates $0.1-0.3$ at RHIC. When combining our results for $η/s$ in the deconfined phase with those from chiral perturbation theory or the resonance gas model in the confined phase we observe a pronounced minimum of $η/s$ close to the critical temperature $T_{\rm c}$.

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