Universal aspects of light halo nuclei

The theoretical status on universal aspects of weakly-bound neutron-rich light nuclei are reviewed, considering few-body approaches. We focus the review on the low-energy properties of light halo nuclei that can be treated within two- and three-body approaches (with one- and two-neutron halos), which are dominated by ss-wave two-body interactions. The representative works studying the large two-neutron halos in light exotic nuclei with short-range interactions show that the general properties associated with the halo neutrons are model independent and obey scaling laws, which are functions of the low-energy observables of the neutron–neutron and neutron–core subsystems, with one additional scale that represents the physics of the three-body system at short-ranges. The scaling laws for the ss-wave two-neutron halos are identified with limit-cycles in a renormalized zero-range three-body model. The necessary basic concepts for interpreting the physics of large halos, and also to treat the zero-range interaction in few-body systems, are given.