Possible Born amplitude for pions

Considerable progress has been made during the last five years towards a possible theory of strong interactions based on real crossing- invariant Born amplitudes for linear Regge trajectories. One outstanding problem is to write, even for external spin-zero pions, a consistent Born amplitude with physically acceptable intercepts and mass spectrum. Recently a method of classifying Born amplitudes was developed by the author (see abstr. A54347 of 1973) making use of the symmetric group. At the same time it was pointed out how the symmetric group could be used to construct new amplitudes using this approach a possible multipion amplitude is constructed. The case of the four-pion amplitude is considered in detail. (12 refs).