...coordinates

These are often referred to as ``center of mass'' and ``relative'' coordinates, respectively. I feel that this is a misleading terminology, because it gives the incorrect impression that one is dealing with a two-body problem. We shall see below that the significance of these coordinates follows from their relationship to the superoperators 137#137 and 138#138 (2.10--2.10) generated by the position operator.

William R. Frensley
Thu Jun 8 17:53:37 CDT 1995