Abstract: We explore extensively new and old, but still unsolved, nuclear structure problems induced by the spin and isospin degree of freedom by using microscopic models which accommodate isoscalar (IS) and isovector (IV) pairing interactions, and also tensor correlations. For the attempt of universal theoretical framework for both nuclear and astrophysical phenomena, we adopt a selfconsistent Hartree-Fock (HF)+random phase approximation (RPA) models embedded the tensor interactions [1], and a state-of-the-art beyond mean field model, Subtracted Second RPA (SSRPA) [2] including the couplings to two-particle two-hole (2p-2h) states. Especially, we study magnetic dipole (M1) [1,2], charge-exchange Gamow-Teller (GT) [2] and spin-dipole excitations. We mention also pigmy and giant resonances induced by the tensor interaction. Our results give a new insight on the quenching of GT sum rule strengths without introducing any free parameters in the selfconsistent microscopic calculations. The SSRPA model is further applied to the β decay half-lives of four semi-magic and magic nuclei: 34Si, 68,78Ni and 132Sn [3]. We show that the inclusion of the 2p-2h configurations in SSRPA model shifts low-lying Gamow-Teller (GT) states downwards, and leads to an increase of the β decay phase space, and consequently reproduce the β decay half-lives dramatically close to the experimental observations. The effect of tensor interaction on the β decay half-life in SSRPA model is also pointed out to change largely the half-lives by about one to two orders of magnitude with respect to the ones obtained without tensor force.

We discuss also possible IS pair condensation in N=Z nuclei by using deformed proton-neutron BCS model taking into account both IS and IV pairing interactions.

References

[1] Shuai Sun, Li-Gang Cao, Feng-Shou Zhang, Hiroyuki Sagawa, and Gianluca Colò, Phys. Rev. C 109, 014321 (2024).

[2] M. J. Yang, H. Sagawa, C. L. Bai, and H. Q. Zhang, Phys. Rev. C 106, 014319 (2022), ; Phys. Rev. C 107, 014325 (2023).