New Topological Aspects of $BF$ Theories
  $BF$ theories defined over non trivial line bundles are studied. It is shown that such theories describe a realization of a non trivial higher order bundle. The partition function differs from the usual one -in terms of the Ray Singer Torsion- by a factor that arises from the non triviality of the line bundles. 
M. I. Caicedo and A. Restuccia