Vector-Tensor Duality
  A dynamical non-abelian two-form potential gives masses to vector bosons via a topological coupling. Unlike in the abelian case, the two-form cannot be dualized to Goldstone bosons. Duality is restored by coupling a flat connection to the theory in a particular way, and the new action is then dualized to a non-linear sigma model. The presence of the flat connection is crucial, which saves the original mechanism of Higgs-free topological mass generation from being dualized to a sigma model. 
Amitabha Lahiri (University of Sussex)