Dual models and relativistic quantum strings

C Rebbi

The string picture of the dual resonance model is reviewed. It is shown that, if we assume for a relativistic string propagating through space time an action proportional to the area of the surface of evolution, the spectrum of states of the corresponding quantum system coincides with the spectrum of states of the conventional dual resonance model and contains only transverse excitations if suitable consistency conditions are met. It is shown also how an interaction among strings can be introduced so as to obtain the dual amplitudes as quantum mechanical transition amplitudes. The main properties of the spectrum of the closed string (Pomeron sector of the conventional dual model) and a generalization to include spin degrees of freedom are discussed. Throughout the article, the results obtained in the theory of the string are compared with the results obtained in the conven- conventional approach to dual models. The reader is assumed to have some familiarity with the general properties of dual models. The review of G. Veneziano in Physics Reports, for instance, may provide the required introduction.