Quantum equivalence of the Freedman-Townsend model and the principal chiral $\sigma$-model

The Freedman-Townsend model is quantized using the Batalin-Vilkovisky approach to Lagrangian quantization of gauge theories with linearly dependent generators. Path integral arguments are then applied to demonstrate the quantum equivalence of the Freedman-Townsend model to the principal chiral $\sigma$-model.