Transport coefficients can be obtained from 2-point correlators using the Kubo formulae. It has been shown that the full leading order result for electrical conductivity and (QCD) shear viscosity is contained in the re-summed 2-point function that is obtained from the 3-loop 3PI re-summed effective action. The theory produces all leading order contributions without the necessity for power counting, and in this sense it provides a natural framework for the calculation. In this article we study the 4-loop 4PI effective action for a scalar theory with cubic and quartic interactions in the presence of spontaneous symmetry breaking. We obtain a set of integral equations that determine the re-summed 2-point vertex function. A next-to-leading order contribution to the viscosity could be obtained from this set of coupled equations.
Renormalized O(N) model at next-to-leading order of the 1/N expansion: Effects of the Landau pole
利用可重整化性重新分析了O（N）模型中1/N展开式次首阶的显收敛贡献。与前一篇文章[G]相比，Fejos等人，Rev. D 80，025015（2009）]，进行额外的减法。我们的数值计算表明，这是必不可少的减少的截断灵敏度的朗道极点的规模以下的一些积分。按照我们的前一篇文章的方法，一个改进的反项拉格朗日构造在两粒子不可约形式主义，使用和不使用辅助场制定。
The Standard Model prediction for $μ$-$e$ scattering at Next-to-Next-to-Leading Order (NNLO) contains non-perturbative QCD contributions given by diagrams with a hadronic vacuum polarization insertion in the photon propagator. By taking advantage of the hyperspherical integration method, we show that the subset of hadronic NNLO corrections where the vacuum polarization appears inside a loop, the irreducible diagrams, can be calculated employing the hadronic vacuum polarization in the space-like region, without making use of the $R$ ratio and time-like data. We present the analytic expressions …
The relation between the specific shear viscosity $η/s$ and the dimensionless jet quenching parameter $\hat{q}/T^3$ in perturbative QCD is explored at next-to-leading order in the coupling constant. It is shown that the relation changes little, although both transport coefficients independently are subject to large modifications at the NLO level. This finding confirms that the relationship is robust.
Based on an extended Skyrme interaction that includes the terms in relative momenta up to sixth order, corresponding to the so-called Skyrme pseudopotential up to next-to-next-to-next-to leading order (N3LO), we derive the expressions of Hamiltonian density and single nucleon potential under general non-equilibrium conditions which can be applied in transport model simulations of heavy-ion collisions induced by neutron-rich nuclei. While the conventional Skyrme interactions, which include the terms in relative momenta up to second order, predict an incorrect behavior as a function of energy fo…
Next-to-leading-order electroweak corrections to $pp \to W^+W^-\to$ 4 leptons at the LHC
我们提出的第一次计算的次到领先的顺序电弱修正的W玻色子对生产的LHC，充分考虑轻子W玻色子衰变和离壳效应。采用现实的事件选择，我们讨论的情况下，是典型的W-玻色子对作为一个信号过程或希格斯玻色子衰变$H\to W W^*$，其中W-玻色子对生产代表一个不可约的背景研究的校正。特别是，我们比较完整的离壳结果，获得治疗的W-玻色子共振在复杂的质量计划，以前的结果在所谓的双极近似，这是基于一个扩展的环路振幅约W共振极点。在小尺度和中等尺度上，特别是在角分布和快度分布上，这两种方法在百分之几的水平上显示出预期的一致性，但在TeV范围内出现了较大的差异。对于横动量分布，差异甚至可以超过10%的水平，在TeV范围内，“背景图”与一个而不是两个共振W玻色子增益的重要性，因为反冲效应。
We perform a complete next-to-leading order calculation of the non-Abelian electric field correlator in a SU($N_c$) plasma, which encodes properties of the plasma relevant for heavy particle bound state formation and dissociation, and is different from the correlator for the heavy quark diffusion coefficient. The calculation is carried out in the real-time formalism of thermal field theory and includes both vacuum and finite temperature contributions. By working in the $R_ξ$ gauge, we explicitly show the results are gauge independent, infrared and collinear safe. The renormalization group equa…
