Unitarity and On-Mass-Shell Analyticity as a Basis for S-Matrix Theories. II

Sets of postulates for S-matrix theories are given and used to construct potentially complete dynamical theories for scattering of strongly interacting particles, based essentially on the unitarity relations and on-mass-shell analyticity of scattering amplitudes. In one formulation, the unitarity relations for stable particles are used to derive the corresponding relations for cuts associated with unstable particle states. In a second formulation, an attempt is made to treat stable and unstable particles on a more equal footing. Crossing symmetries and decomposition laws for single-particle poles appear as consequences of the postulates.