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arXiv 0902.4829hep-ph
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手征微扰理论中介子气体的输运系数和共振态

Transport coefficients and resonances for a meson gas in Chiral Perturbation Theory

D. Fernandez-Fraile, A. Gomez Nicola

摘要:

我们提出了一个系统的方法来计算输运系数的介子气体(特别是,我们分析了π介子气体)在低温下的手征微扰理论(ChPT)的最新结果。我们的方法是基于费曼图的研究,考虑到在等离子体中的碰撞,通过非零的粒子宽度。这意味着标准ChPT功率计数方案的修改。我们讨论了么正性的重要性,它允许一个准确的高能量描述的散射振幅,动态生成的$ρ(770)$和$f_0(600)$介子。我们的结果是兼容的动力学理论的分析,无论是在非相对论性非常低的$T$制度和附近的过渡。我们显示的行为与温度的电导率和热导率,以及剪切和体积粘度。我们得到,体粘度是可以忽略不计的剪切粘度,除了附近的手征相变,共形异常可能会导致更大的体效应。研究了输运系数的不同渐近极限、大$N_c$标度以及在重离子碰撞中的应用。

英文摘要:

We present recent results on a systematic method to calculate transport coefficients for a meson gas (in particular, we analyze a pion gas) at low temperatures in the context of Chiral Perturbation Theory (ChPT). Our method is based on the study of Feynman diagrams taking into account collisions in the plasma by means of the non-zero particle width. This implies a modification of the standard ChPT power counting scheme. We discuss the importance of unitarity, which allows for an accurate high energy description of scattering amplitudes, generating dynamically the $ρ(770)$ and $f_0(600)$ mesons. Our results are compatible with analyses of kinetic theory, both in the non-relativistic very low-$T$ regime and near the transition. We show the behavior with temperature of the electrical and thermal conductivities as well as of the shear and bulk viscosities. We obtain that bulk viscosity is negligible against shear viscosity, except near the chiral phase transition where the conformal anomaly might induce larger bulk effects. Different asymptotic limits for transport coefficients, large-$N_c$ scaling and some applications to heavy-ion collisions are studied.

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