We consider the $U(1)$ gauge theory on a four-dimensional torus, where the instanton number is restricted to an integral multiple of $p$. This theory possesses the nontrivial higher-group structure, which can be regarded as a generalization of the Green--Schwarz mechanism, between $\mathbb{ Z}_q$ $1$-form and $\mathbb{ Z}_{ pq}$ $3$-form symmetries. Here, $\mathbb{ Z}_q$ is a subgroup of the center of~$U(1)$. Following the recent study of the lattice construction of the $U(1)/\mathbb{ Z}_q$ principal bundle, we examine how such a structure is realized on the basis of lattice regularization.
Categories: hep-th hep-lat