This volume grew from a Special Session in }~thematical Physics organized as a part of the 774th Heeting of the American }~thematical Society in Boulder, Colorado, ,27-29 l~rch, 1980. The organizers attempted to include a mix of mathematicians, physi­ cists and chemists. As interest in the session increased and as it became clear that a significant number of leading contributors would be here, we were offered the opportunity to have these pro­ ceedings published by Plenum Press. We would like first to express our thanks to Plenum Press, to the American Hathematical Society, and to the University of Colorado Graduate School, and in particular, respectively, to James Busis, Dr. William LeVeque, and Vice Chancellor Hilton Lipetz, for their help in this undertaking. We would also like to thank Burt Rashbaum and }~rtha Troetschel of the Department of l~thematics and Karen Dirks, Donna Falkenhein, Lorraine Volsky, Gwendy Romey, and Leslie Haas of the Joint Institute for labora­ tory Astrophysics for their excellent help in the preparation of these proceedings. The session took on an international character, representing the countries Federal Republic of Germany, India, Belgium, Peoples Republic of China, Switzerland, Iran, Hexico, GerPlan Democratic Republic, England, and the United States. In all there were fi­ nally 37 speakers and all have contributed to this volume. The success of the meeting is above all due to them.