Abstract

Just as conventional global symmetries result in a conserved particle number, higher-form global symmetries are associated with a conserved density of higher dimensional objects, such as strings or branes. Many well-known systems possess such symmetries. I will present an overview of the applications of such symmetries and discuss the prospect of using them to enlarge the usual Landau classification of the phases of matter. I will then describe the construction of a continuum Landau-Ginzburg theory to describe the spontaneous breaking of a higher-form symmetry. As the order parameter is an operator that creates a string, the framework can be thought of as a kind of “mean string field theory” that provides a non-perturbative description where effective strings can be created and destroyed. I will argue that many aspects of higher form symmetries — including the phase structure, the behavior of line operators, and the dynamics of Goldstone modes — can be transparently understood in this framework.