Covariant Hamiltonian formalisms for particles and antiparticles

The hyperplane and proper time formalisms are discussed mainly for the spin-half particles in the quantum case. A connection between these covariant Hamiltonian formalisms is established. It is showed that choosing the space-like hyperplanes instantaneously orthogonal to the direction of motion of the particle the proper time formalism is retrieved on the mass shell. As a consequence, the relation between the St"uckelberg-Feynman picture and the standard canonical picture of quantum field theory is clarified.