It is shown that the anomalously large double binding energy differences for even-even N = Z nuclei are a consequence of Wigner's SU(4) symmetry. These, and similar quantities for odd-mass and odd-odd nuclei, provide a simple and distinct signature of this symmetry in N≃Z nuclei
The nucleus is a unique laboratory in physics — a quantum many-body system comprising two types of fermion, the neutron and proton, differing in charge but otherwise essentially identical in their behaviour. The fact that the strong interaction between these fermions is largely independent of charge results in striking symmetries in nuclei. This neutron–proton exchange invariance is encompassed in the elegant concept and formalism of Wigner's isotopic spin — or isospin. The impact of isospin symmetry is maximal near the N=Z line where nuclei have equal numbers of neutrons and protons, and studies involving isospin effects have undergone a resurgence in recent years as such nuclei become more readily accessible. In this review we discuss three isospin-related phenomena: the elegant isospin symmetry of excited analogue states in nuclei, the origin of the extra binding for nuclei with equal numbers of neutrons and protons and the exotic phenomenon of neutron–proton pairing. These three topics, all of considerable current interest, demonstrate the power, simplicity and modern relevance of the isospin concept
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.