Self-Consistent Covariant Descriptions of Spin-Isospin Resonances

At present, spin-isospin excitations in nuclei become one of the central topics in nuclear physics and astrophysics. Basically, a systematic pattern of the energy and collectivity of these resonances could provide direct information on the spin and isospin properties of the in-medium nuclear interaction, and the equation of state of asymmetric nuclear matter. Furthermore, a basic and critical quantity in nuclear structure, the neutron skin thickness, can be determined indirectly by the sum rule of spin-dipole resonances (SDR) or the excitation energy difference between isobaric analog states (IAS) and Gamow-Teller resonances (GTR). More generally, spin-isospin resonances allow one to attack other kinds of problems outside the realm of nuclear structure, like the description of neutron star and supernova evolutions, the β-decay of nuclei which lie on the r-process path of stellar nucleosynthesis, and so on. In this work [1], a fully self-consistent charge-exchange relativistic random phase approximation (RPA) based on the relativistic Hartree-Fock (RHF) approach [2,3] is established. The self-consistency is verified by the so-called IAS check. The excitation properties and the non-energy weighted sum rules of the GTR and SDR are well reproduced in the doubly magic nuclei 48Ca, 90Zr and 208Pb without any readjustment of the particle-hole residual interaction. Furthermore, the importance of exchange diagram contributions is demonstrated.(author)