Central extensions of higher groups: Green-Schwarz mechanism and 2-connections

We study the smooth $2$-group structure arising in the presence of quantum field theory with one-form symmetry. We acquire $2$-group structures obtained by a central extension of the zero-form symmetry by the one-form symmetry. We determine that the existence of a $2$-group structure is guaranteed by Chern--Simons levels. We further verify how we will be able to provide a fix to the current $2$-group problems by using the bibundle model. We outline the principal $2$-connection theory with respect to such $2$-group and compare it with the ansatz obtained from the Green--Schwarz mechanism. We further propose the existence of smooth $\infty$-group symmetries in quantum field theory.