PI-NNN-NNN PROBLEM - CONNECTEDNESS, TRANSITION AMPLITUDES, AND QUASI-PARTICLE APPROXIMATION

In this paper we review the present status of the pi NNN-NNN problem. In particular, we reconsider the chain-labeled approach recently propo sed by us, and identify a class of graphs, previously overlooked, whic h prevents the kernel of the corresponding pi NNN-NNN equations from b eing connected. We propose some approximate schemes, yielding connecte d-kernel equations. A generalization of the residue method allows us t o relate the transition amplitudes for the coupled pi NNN-NNN system t o the chain-labeled formalism. The quasiparticle approach is extended to the present situation, where emission/absorption of particles is al lowed. The open problems for the pi NNN-NNN system in light of the pre sent and of previous approaches are finally discussed.