Global Structure, Non-Invertible PQ Symmetry, and the DFSZ Domain Wall Problem

by Dr Sungwoo Hong (KAIST)

Thursday 7 May 2026, 16:00 → 17:30 Asia/Seoul

Room 1423 (KIAS)

Title: Global Structure, Non-Invertible PQ Symmetry, and the DFSZ Domain Wall Problem

Speaker: Sungwoo Hong

Abstract: 

In this talk, I will introduce the notion of global aspects in the physics of particles and topological defects by taking a concrete example of DFSZ axion model. In particular, I will describe how various global structures play important roles in the domain wall problem of the DFSZ axion model. A precise identification of the axion string–domain wall network—and hence the true nature of the domain wall problem—becomes possible by recognizing a discrete overlap between the Peccei-Quinn symmetry and the SM gauge group.

An elegant solution to the domain wall problem can also be realized by introducing another global structure shared between the color and family gauge groups, which gives rise to discrete non-invertible Peccei-Quinn symmetries. This discrete non-invertible symmetry can then be slightly broken by small instanton effects in a UV completion in the form of an SU(9) color–flavor unification. In this part of talk, if time is permitted, I will discuss construction of non-invertible symmetry defect operator and its action on both local and line operators in the language of "partial gauging".