Orbifolds of topological quantum field theories

Abstract: The orbifold construction via topological defects in quantum field theory can either be understood as a state sum construction internal to a given ambient theory, or as the procedure of (identifying and) gauging ordinary and "non-invertible" symmetries. Here we explain how this is rigorously understood in the case of topological QFTs. We provide various examples and outline general features, also of relevance for full QFT.