Comparison of point form and front form Hamiltonian methods

Interacting Poincare generators for both front form (FF) and point form (PF) are obtained by integrating interaction Lagragians over appropriate space-like surfaces. For finite degree of freedom systems mass operators in both FF and PF can be constructed using the Bakamjian-Thomas (BT) procedure. Velocity states are used to calculate matrix elements of the four-momentum operator in PF from which a mass operator is constructed. Moreover, velocity states keep the addition rules for angular momentum simple and allow the Fock space to be truncated in a covariant way. As an example we calculate the decay matrix element for the process Δ → Nπ in the constituent quark model