Description
There is by now a beautiful theory of generalized symmetries for 2D QFTs based in the physics of topological line defects and the mathematics of tensor categories. I will sketch a generalization of this theory to the setting of relative 2D QFTs (i.e. QFTs which live at the boundary of a bulk 3D topological order), emphasizing various new algebraic structures that arise, such as hypergroups. This theory is particularly rich when applied to the chiral half of a CFT, and I will spend most of the time unpacking this special case and discussing applications.