nucl-th digest · Mar 23, 2017

Influence of complex configurations on properties of pygmy dipole resonance in neutron-rich Ca isotopes

Starting from the quasiparticle random phase approximation based on the Skyrme interaction SLy5, we study the effects of phonon-phonon coupling~(PPC) on the low-energy electric dipole response in

^{40 - 58}

Ca. Using the same set of parameters we describe available experimental data for

^{40, 44, 48}

Ca and give prediction for

^{50 - 58}

Ca. The inclusion of the PPC results in the formation of low-energy

1^{-}

states. There is an impact of the PPC effect on low-energy

E 1

~strength of

^{40, 44, 48}

Ca. The PPC effect on the electric dipole polarizability is discussed. We predict a strong increase of the summed

E 1

~strength below 10MeV, with increasing neutron number from

^{48}

Ca till

^{58}

Ca.

nucl-thPRC(2017)·18 citations

Third-order particle-hole ring diagrams with contact-interactions and one-pion exchange

N. Kaiser

The third-order particle-hole ring diagrams are evaluated for a NN-contact interaction of the Skyrme type. The pertinent four-loop coefficients in the energy per particle $E ˉ (k_{f}) \sim k_{f}^{5 + 2 n}$ are reduced to double-integrals over cubic expressions in euclidean polarization functions. Dimensional regularization of divergent integrals is performed by subtracting power-divergences and the validity of this method is checked against the known analytical results at second-order. The complete $O (p^{2})$ NN-contact interaction is obtained by adding two tensor terms and their third-order ring contributions are also calculated in detail. The third-order ring energy arising from long-range $1 π$ -exchange is computed and it is found that direct and exchange contributions are all attractive. The very large size of the pion-ring energy, $E ˉ (k_{f 0}) ≃ - 92$ MeV at saturation density, is however in no way representative for that of realistic chiral NN-potentials. Moreover, the third-order (particle-particle and hole-hole) ladder diagrams are evaluated with the full $O (p^{2})$ contact interaction and the simplest three-ring contributions to the isospin-asymmetry energy $A (k_{f}) \sim k_{f}^{5}$ are studied.

nucl-thEPJA(2017)·10 citations

Thursday·March 23, 2017

Influence of complex configurations on properties of pygmy dipole resonance in neutron-rich Ca isotopes

Third-order particle-hole ring diagrams with contact-interactions and one-pion exchange

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