ABSTRACT
There is a conserved current and a constant of the motion for each independent infinitesimal symmetry transformation. This represents a general feature of the canonical formalism, often referred to as Noether’s theorem: symmetries imply conservation laws. This theorem is cited in the original German and in the English translation, which Einstein is known to have encouraged strongly. This chapter describes the treatment of first and second class restraints and Dirac brackets. The main problem to deriving the Hamiltonian from the Lagrangian is the presence of constraints. Primary constraints are either imposed on the system or arise from the structure of the Lagrangian itself.
