U nirxr.sity, Fukui § 1. Introduction As was stressed in Part I and the preceding chapters, the structure of the c6mposite particles seem. to be intimately connected with the nature of more fundamental dynamical laws which will reveal themselves beyond the limit of applicability of the point model. In fact, in the preceding chapters, we have confined our discussions to the problems of the .symmetry properties and of the mass relations among composite particles without entering into the details

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... f dynan;:tic;:al aspects pf the pre,sent model. Nevertheless, it would be a necessary task to examine how the composite particles could be described in the frame-work of the orthodqx qm;mtum field. theories as far as one intends to clarify .the physical implications of the limit of applicability of the present-day theory. In this chapter, we shall construct a general formalism of treating the Sakata model by means of quantum field theory and ·derive several con· sequences, bearing in mind that our theory applied to the present model would have a physical reliability only in the corresponding" theoretical sense. For this purpose, it may be natural to separate our investigations into two steps. In the first place, we shall formulate our problem in a general form on the basis of the general principles usually adopted in quantum field theory and make clear the main features of composite 'particles in connection with their propagation charact~rs ( §2 a~d §3). The res~lts. thus obtained may provide a clue to the future development of the theory of the Sakata model. The second step· is to examine in detail: the dynamical aspects of the theory by taking some trial forms of interaction among fundamental particles. In this approach, however, we shall meet with the well-known difficulty of treating strong interactions because of the lack of any useful method of calculation for such interaction; we have to be satisfied 'with less reliable results based on rough approximation s ( §4).