Nonperturbative effects from gauging higher-form symmetries

Higher-form symmetries are pivotal in understanding the global structure of quantum field theory. In this talk, I review the notion of higher-form symmetry in Yang-Mills theory and demonstrate that gauging it is associated with fractional instantons that lead to non-perturbative effects. Time permitting, I will discuss two examples. First, the Standard Model possesses a 1-form global symmetry, and gauging it gives rise to new baryon- and lepton-number-violating processes. Second, the axion-Yang-Mills system features an emergent 2-form symmetry, and gauging it results in a 3-form gauge theory that accurately captures the interplay between the light (axion) and heavy (hadronic) degrees of freedom in the infrared.