On 3-dimensional Homotopy Quantum Field Theory, I
  Given a discrete group G and a spherical G-fusion category whose neutral component has invertible dimension, we use the state-sum method to construct a 3-dimensional Homotopy Quantum Field Theory (HQFT) with target the Eilenberg-MacLane space K(G,1). 
Vladimir Turaev, Alexis Virelizier
math.QA math.GT