Title: Tensor correlations and nuclear structure

Speaker: Prof. Hiroyuki Sagawa (University of Aizu, Aizu-Wakamatsu, Fukushima, Japan)

We study the effect of tensor correlations on the isotope and the isotone dependence of single-particle energies in N="82" isotones and Z="50" isotopes. The importance of the tensor correlations is pointed out to reproduce the isospin dependence of empirical energy splitting around the Fermi surface. As spin dependent excitation mode, the Magnetic dipole (M1), charge-exchange Gamow-Teller and spin-dipole (SD) excitations are studied by using a fully self-consistent Skyrme Hartree-Fock plus Random Phase Approximation (HF+RPA) formalism which includes the tensor interaction. It is found that the tensor correlations have a unique, multipole-dependent effect on the SD excitations,that is, they produce softening of 1^- states, but hardening of 0^- and 2^- states. We compare our results with recent measurements, showing that our choice of tensor terms improves the agreement with experiment. The robustness of our results is supported by the analytic form of the tensor matrix elements. The spin and spin-isospin instabilities of nuclear matter are also studied with the Skyrme energy density fuctionals plus the tensor interactions.

Even at zero temperature, we still ignore many features of the equation of state of nuclear matter, namely, of the relation between pressure and density of a system made up with nucleons. The problem is not merely academic, in keeping with its impact for compact astrophysical objects like neutron stars. In this seminar we discuss to what extent the equation of states can be determined by studying the vibrational modes of atomic nuclei. We also briefly compare with other approaches. The emphasis is put on basic ideas that can link together nuclear theory, nuclear experiments, and astrophysical applications.