LAGRANGIAN APPROACH OF THE FIRST-CLASS CONSTRAINED SYSTEMS

We show how to systematically derive the exact form of local symmetrie s for the Abelian Proca and CS models, which are converted into first- class constrained systems by the BFT formalism, in the Lagrangian form alism. As a result, without resorting to a Hamiltonian formulation we obtain the well-known U(1) symmetry for the gauge-invariant Proca mode l, while showing that for the CS model there exist novel symmetries as well as the usual symmetry transformations.