论文标题
离散的theta角度，对称性和异常
Discrete Theta Angles, Symmetries and Anomalies
论文作者
论文摘要
在各个维度上的仪表理论通常接收离散的theta角，这是由于用额外的对称性受保护的拓扑（SPT）阶段测量全局对称性而产生的。我们讨论了通过将量规理论与拓扑量子场理论（TQFT）耦合，全局对称性和't Hooft异常如何取决于离散的theta角度。我们观察到，衡量参与对称扩展的Abelian亚组对称性，额外的SPT阶段会导致一种新理论，并具有出现的Abelian Symmetry，也参与了对称性扩展。仪表理论的对称扩展由来自SPT阶段的离散theta角控制。我们发现，离散的theta角可以通过$ su（n），su（n）/\ mathbb {z} _k $或$ so（n）$ gauge组以及各种3D和2D量学理论导致4D QCD中的两组对称性。
Gauge theories in various dimensions often admit discrete theta angles, that arise from gauging a global symmetry with an additional symmetry protected topological (SPT) phase. We discuss how the global symmetry and 't Hooft anomaly depends on the discrete theta angles by coupling the gauge theory to a topological quantum field theory (TQFT). We observe that gauging an Abelian subgroup symmetry, that participates in symmetry extension, with an additional SPT phase leads to a new theory with an emergent Abelian symmetry that also participates in a symmetry extension. The symmetry extension of the gauge theory is controlled by the discrete theta angle which comes from the SPT phase. We find that discrete theta angles can lead to two-group symmetry in 4d QCD with $SU(N),SU(N)/\mathbb{Z}_k$ or $SO(N)$ gauge groups as well as various 3d and 2d gauge theories.
