Multichannel quantum defect and reduced R-Matrix

This work demonstrates that the Multichannel Quantum Defect Theory and the Reduced R-Matrix are formally related and physically equivalent; both theories describe not only the internal dynamics but also the interactions in space of eliminated channels. The Multichannel Quantum Defect Theory is, according to present approach, a general framework relating collision matrices of two reaction systems which differ only in dynamics of eliminated channels. (authors)