Correlations in nuclear collective observables
The evolution of structure in atomic nuclei with neutron and proton number depends on a competition of different interactiuons, primarily among the valence nucleons. The evolution will be discussed in the context of correlations among a set of observables reflecting both single particle and collective behavior. Following this, the roles of pairing and the proton-neutron interaction will be discussed, including experimental methods to extract the latter from binding energies. The implications of new mass measurements will be discussed. Simple theoretical ideas iwll be used to interpret the emperical p-n interactions, which will also be compared with recent density functional theory calculations.