Title: QCD Shear Viscosity at (almost) NLO Show Chinese title

Title: QCD 剪切粘度在（几乎）NLO

Abstract: We compute the shear viscosity of QCD with matter, including almost all next-to-leading order corrections -- that is, corrections suppressed by one power of $g$ relative to leading order. We argue that the still missing terms are small. The next-to-leading order corrections are large and bring $\eta/s$ down by more than a factor of 3 at physically relevant couplings. The perturbative expansion is problematic even at $T \simeq 100$ GeV. The largest next-to-leading order correction to $\eta/s$ arises from modifications to the qhat parameter, which determines the rate of transverse momentum diffusion. We also explore quark number diffusion, and shear viscosity in pure-glue QCD and in QED. Show Chinese abstract

Abstract: 我们计算了包含几乎所有次领头阶修正的QCD的剪切粘度——即相对于领头阶修正被一个幂次抑制的修正，也就是相对于$g$的修正。 我们认为仍然缺失的项是小的。 次领头阶修正很大，并且在物理相关的耦合常数下将$\eta/s$降低了超过三倍。 即使在$T \simeq 100$GeV 时微扰展开也是有问题的。 对$\eta/s$的最大次领头阶修正来自于 qhat 参数的修改，该参数决定了横向动量扩散的速率。 我们还研究了夸克数扩散以及纯胶子QCD和QED中的剪切粘度。