Bulk viscosity is an important transport coefficient that exists in the hydrodynamical limit only when the underlying theory is non-conformal. One example being thermal QCD with large number of colors. We study bulk viscosity in such a theory at low energies and at weak and strong ’t Hooft couplings when the temperature is above the deconfinement temperature. The weak coupling analysis is based on Boltzmann equation from kinetic theory whereas the strong coupling analysis uses non-conformal holographic techniques from string and M-theories. Using these, many properties associated with bulk viscosity may be explicitly derived.

中文翻译：

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弱和强 't Hooft 联轴器的体积粘度

体积粘度是一个重要的输运系数，仅在基础理论非保形时才存在于流体动力学极限中。一个例子是具有大量颜色的热 QCD。当温度高于去限制温度时，我们在这种理论中研究低能和弱和强 't Hooft 耦合下的体积粘度。弱耦合分析基于动力学理论的玻尔兹曼方程，而强耦合分析使用弦理论和 M 理论的非共形全息技术。使用这些，可以明确导出与体积粘度相关的许多特性。