The aim of these notes is to provide an elementary introduction to some of the basic elements of exact S-matrix theory. This is a large subject, and only the beginnings will be covered here. A particular omission is any serious discussion of the Yang-Baxter equation; instead, the focus will be on questions of analytic structure, and the bootstrap equations. Even then, what I have to say will only be a sketch of the simpler aspects. The hope is to give a hint of the many curious features of… CONTINUE READING