Multichannel quantum-defect theory for anisotropic interactions

We present a general formulation of multichannel quantum-defect theory (MQDT) for anisotropic long-range potentials. The theory greatly expands the types of interactions, including complex interactions involving molecules, that can be treated and understood systematically. It promotes MQDT into a general theory of interactions and establishes a foundation for new classes of quantum theories for chemical reactions, few-body systems, and many-body systems.