Correlations and Strong Interactions

Abstract

Although Quantum Chromodynamics (QCD) is considered at present to be the best candidate for a theory of strong interactions, it is not directly applicable to the most interesting and important aspects of strong interactions, i.e. to multiparticle production, which is a \soft" process. Instead one uses lattice QCD which predicts in principle the hadronic mass spectrum. The fact that the main content of Hagedorn's statistical bootstrap is also the mass spectrum proves the intuitive power of this approach, developed many years before the advent of QCD.Why is the mass spectrum so essential for the understanding of strong interactions? In the Hagedorn theory the answer lies in the very derivation of this spectrum. The bootstrap \closes" only for a speci c analytical form of this spectrum (the exponential one) and the fact that the bootstrap closes is the re ection of the strong nature of the interaction.In the following I shall provide a further argument for the importance of the mass spectrum by relating it to another important phenomenological characteristic of strong interactions,namely the multiplicity distribution P(n). I shall then show that the knowledge of this distribution is equivalent with the knowledge of correlations. The remainder of the talk will be devoted to a short review of the most important developments in the eld of correlations in the last 5 years.