手征核力简介

A brief introduction to chiral nuclear forces

论文的主旨是为从事核结构理论研究的青年物理学家介绍基于手征有效场论的微观核力.论文将侧重解释手征有效场论的基本概念,以达核结构与少体核物理两个研究领域相互交流之目的.我从静电学的多极展开出发,指出有效场论本质是近似理论,是以低、高两个能标之比为小量的泰勒展开,而该例子中体现的power counting(数幂规则)是任何有效场论的基石.接着,Weinberg对手征理论中的费曼图作power counting的一般方法被引入,量子色动力学的手征对称性及其自发破缺对这种power counting方法的成功起到很重要的作用.在剩下的篇幅中,重整化与power counting的关系将是讨论的重点.我将阐述重整化如何帮助我们更好地理解短程核力.

The present manuscript is based on the lecture given at the ＂Seventh symposium on covariant density functional theory in atomic nuclear physics＂. It serves as a very brief introduction to the development of nucleon-nucleon interactions from chiral effective field theory, with the targeted audience being young nuclear physicists working on many-body nuclear theory. I start with the basic idea of effective field theory that separation of scales facilitates the expansion in the small ratio of a low-energy scale to a high-energy one. This idea will be illustrated by the classical example of multipole expansion in electrostatics. In the course of doing that, the concept of power counting is broug- ht up, which is one of the pillar stones of any effective field theory. In the presence of quantum effects, a general tool due to Weinberg is introduced, whose goal is to estimate the size of quantum fluctuations that are often manifested by Feynman diagrams. Spontaneous breaking of chiral symmetry in quantum chromodynamics makes this tool particu- larly useful in counting diagrams in powers of external momenta, because the pions always couple to each other and to non-Goldstone particles in powers of momenta. But the presumption of this counting rule is renormalizability of all diagrams at the same order. The reset of the paper focuses on the interplay between renormalization and power counting, in the context of chiral nuclear forces.