Universit\u00e9 de Caen Normandie
Experimental data on α\alpha-particle inelastic scattering for monopole excitations in 24^{24}Mg in the excitation-energy region ExE_{\rm x}==99-2525 MeV, obtained at the iThemba Laboratory for Accelerator Based Sciences (iThemba LABS), have been analyzed within a fully self-consistent quasiparticle random-phase approximation (QRPA) framework using two Skyrme parametrizations. A good overall agreement with the experimental data is achieved, particularly with the SkPδ^{\delta} force, which corresponds to a low nuclear incompressibility of KK_{\infty}==202202 MeV. Extraction of energy scales, by means of wavelet analysis, characterizing the observed fine structure of the isoscalar giant monopole resonance (ISGMR) as well as the low-energy region 1010-1818 MeV of the deformation-induced monopole-quadrupole coupling (MQC) in order to investigate the damping mechanism contributing to their decay widths. Characteristic energy scales are extracted from the fine structure using continuous wavelet transforms. The experimental results are compared to QRPA calculations employing the Skyrme parameterizations SkPδ^{\delta} and SVbas. A significant, if not decisive, impact of the MQC strength on the wavelet power spectra is observed across the entire excitation-energy range of 1010-2424 MeV. Wavelet features derived from the QRPA and from unperturbed two-quasiparticle (2qp) monopole strengths are compared. The results demonstrate that the residual interaction plays a key role in reproducing realistic wavelet powers and characteristic energy scales. Overall, a continuous range of scales δE\delta E==200200-10001000 keV is obtained rather than distinct isolated scales. The deformation softness of 24^{24}Mg is found to significantly influence both the monopole strength distribution and the wavelet characteristics.
In this work, we study the effects of Λ\Lambda-hyperons on neutron star properties employing a metamodel framework for the equation of state (EoS). Different choices for defining the hyperonic couplings with different levels of parametric freedom are discussed. In all models, the predicted NS maximum masses are reduced compared with the purely nucleonic composition as expected. In the case of relating hyperonic couplings via SU(6)SU(6)-symmetry arguments to the nucleonic ones, we find that NS radii for intermediate mass stars are shifted to higher values compared with purely nucleonic stars, in agreement with the existing literature. However, allowing for more freedom for the hyperonic couplings, the effect is strongly reduced, and the distributions in the NS mass-radius plane of models with and without hyperons become very close. We have also investigated how different nucleonic density functionals influence the hyperon matter composition and neutron star properties.
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