AI 中文总结
本文综述QCD的对称性，重点阐述对低能核物理重要的手征对称性及其破缺，说明其为描述低能π介子与核子的手征微扰论提供基础，揭示QCD对称性对强子相互作用的约束作用。
AI 中文摘要
量子色动力学（QCD）是描述强相互作用的理论，其以夸克和胶子为基本自由度；而低能核物理研究的是质子、中子、π介子等强子。对称性在这两种强相互作用系统的描述之间建立了系统联系。本文旨在综述QCD的对称性，并解释这些对称性如何约束强子相互作用。手征对称性在夸克质量为零的极限下于QCD中显现，对低能核物理尤为重要。结合其明显对称性破缺与自发对称性破缺，手征对称性为手征微扰论奠定了基础，该理论是描述低能下π介子与核子的有效场论。
英文摘要
QCD, the theory of the strong interactions, is formulated in terms of quarks and gluons, while low-energy nuclear physics deals with hadrons such as protons, neutrons, and pions. Symmetries establish a systematic connection between these two descriptions of strongly-interacting systems. The objective of this article is to review the symmetries of QCD and to explain how they constrain hadronic interactions. Chiral symmetry, which emerges in QCD in the limit of massless quarks, is of particular importance for low-energy nuclear physics. Together with its explicit and spontaneous breaking, chiral symmetry provides the basis for chiral perturbation theory, the effective field theory describing pions and nucleons at low energies.
Comments25 pages, 7 figures. Contribution to the Encyclopedia of Nuclear Physics
