Center for Theoretical Physics of the Universe (CTPU)

# Higher-form symmetries and 3-group in axion electrodynamics

## by Dr Ryo Yokokura (KEK)

Asia/Seoul
On-line seminar

### On-line seminar

Description
We study higher-form symmetries in a low-energy effective theory of a massless axion coupled with a photon in $(3+1)$ dimensions. It is shown that the higher-form symmetries of this system are accompanied by a semistrict 3-group (2-crossed module) structure, which can be found by the correlation functions of symmetry generators of the higher-form symmetries. We argue that the Witten effect and anomalous Hall effect in the axion electrodynamics can be described in terms of 3-group transformations.