Boundary conditions as Dirac constraints

In this article we show that boundary conditions call be treated as Lagrangian and Hamiltonian constraints, Using the Dirac method: we find that boundary conditions are equivalent tu all infinite chain of second class constraints. which is a new feature ill the context of constrained systems. Constructing the Dirac brackets and the reduced phase space structure for different boundary conditions, we show why mode expanding and then quantizing a field theory with boundary conditions is the proper wag. We also show that ill a quantized field theory subjected to the mixed boundary conditions, the field components are non-commutative.