Chew-Frautschi plots

Geoffrey Chew and Steven Frautschi, in 1961, will propose that mesons, when plotted with their angular momentum, against the squared of their masses, will fall into straight line trajectories. These are called Regge trajectories.

This school of thought, from which string theory emerged, was led by Geoffrey Chew. The theory relied on the self consistency of the S-matrix. Remember, the S-matrix is a mathematical description of the collision of particles. This S-matrix in Chew's theory obeyed a rigorous set of mathematical properties. In fact, they were so restrictive, that only one solution could be possible. This was known as the "bootstrap approach." Chew's theory was based entirely on the S-matrix, hence, it was called S-matrix theory. This is to distinguish it from the actual S-matrix itself, which is used more broadly by physicists. The S-matrix theory was a distinct framework from quantum field theory. The notion of an elementary particle is different in each of these theories. In quantum field theory, an elementary particle is fundamental. However, in the S-matrix theory, there are an infinite series of particles, hence, none can be truly fundamental. However, it should be noted that the S-matrix theory is extremely difficult to calculate with. It is hard to extract usable data from the S-matrix theory.