论文标题
半经典近似符合Keldysh-Schwinger图解技术：标量$φ^4 $
Semiclassical Approximation meets Keldysh-Schwinger diagrammatic technique: Scalar $φ^4$
论文作者
论文摘要
我们在两种方法中研究了非平衡量子场从高度激发的初始状态中的演变：标准的Keldysh-Schinginger图技术和半经典膨胀。我们明确证明，如果耦合恒定$ g $和木板常数$ \ hbar $同时同时小，则这两种方法是重合的。另外，我们讨论了扰动方法的循环图，这些图是通过半经典扩展的主要顺序概述的。例如，我们考虑在领先的半经典顺序下对标量场理论的剪切粘度。我们介绍了统一半经典和图形方法的新技术，并打开了执行半经典贡献的可能性。
We study the evolution of the non-equilibrium quantum fields from a highly excited initial state in two approaches: the standard Keldysh-Schwinger diagram technique and the semiclassical expansion. We demonstrate explicitly that these two approaches coincide if the coupling constant $g$ and the Plank constant $\hbar$ are small simultaneously. Also, we discuss loop diagrams of the perturbative approach, which are summed up by the leading order term of the semiclassical expansion. As an example, we consider shear viscosity for the scalar field theory at the leading semiclassical order. We introduce the new technique that unifies both semiclassical and diagrammatic approaches and open the possibility to perform the resummation of the semiclassical contributions.
