Physics Division Colloquium - 8 Oct 1999

Hadron physics is the study of the spectroscopy and electromagnetic and mutual interactions of mesons and baryons, under normal conditions and also at extreme conditions of high temperature and density. A primary goal is an elucidation of the role that the quarks and gluons of Quantum Chromodynamics (QCD) play in determining these hadronic properties, and all the world's high-energy accelerator facilities host experiments focusing on this task. Global symmetries can provide constraints and relations between observables but they cannot open up hadrons and expose the QCD degrees of freedom. That requires a nonperturbative theoretical framework whose primary elements are those quarks and gluons and, of particular importance in QCD, one that can provide a unified description of short- and large-distance phenomena. I will describe the application of one such contemporary framework: the Dyson-Schwinger equations. The simplest of these equations is familiar to all as the Gap Equation in the BCS theory of superconductivity, while another familiar member of the family is the relativistic Bethe-Salpeter bound state equation. The complex of equations appears formidable but nevertheless its analysis facilitates an intuitive understanding and correlation of phenomena as diverse as the low mass and weak interactions between pions and the deconfinement of quarks in the core of dense astrophysical objects.

ANL Physics Division Colloquium Schedule