标题： 场论和弦论中一类没有群作用的选择规则 显示英文标题

标题： On a class of selection rules without group actions in field theory and string theory

摘要： 我们讨论了一类选择规则，这些规则满足以下条件：i) 不来自场的群作用；ii) 在微扰理论的树级上精确成立；iii) 随着圈阶数的提高而越来越被违反；iv) 最终会归结为与普通群对称性相关的选择规则。 我们从基本的场论例子开始，其中场由共轭类而非群表示标记，并讨论了使用融合代数或超群的一般化情况。 我们还讨论了这类选择规则如何在弦理论中自然出现，例如对于非阿贝尔 orbifold 或其他具有非可逆世界面对称性的案例。 显示英文摘要

摘要： We discuss a class of selection rules which i) do not come from group actions on fields, ii) are exact at tree level in perturbation theory, iii) are increasingly violated as the loop order is raised, and iv) eventually reduce to selection rules associated with an ordinary group symmetry. We start from basic field-theoretical examples in which fields are labeled by conjugacy classes rather than representations of a group, and discuss generalizations using fusion algebras or hypergroups. We also discuss how such selection rules arise naturally in string theory, such as for non-Abelian orbifolds or other cases with non-invertible worldsheet symmetries.