Orbifold in 3d TFT

If a field theory comes with a group action that is implemented by certain defects, orbifolding the theory means, in its most basic form, to pass to a fixed point theory. After reviewing the more general 2-dimensional case, where orbifolds of a TFT can be described as certain "internal Frobenius algebras", this talk focuses on orbifolds of 3d TFTs where data similar to internal spherical fusion categories becomes relevant. An example of Reshitikin-Turaev type will be discussed. This is ongoing work with Nils Carqueville and Ingo Runkel.