Self-consistent separable random-phase approximation for Skyrme forces: Giant resonances in axial nuclei

Abstract

We formulate the self-consistent separable random-phase-approximation (SRPA) method and specify it for Skyrme forces with pairing for the case of axially symmetric deformed nuclei. The factorization of the residual interaction allows to avoid diagonalization of high-rank RPA matrices, which dramatically reduces the computational expense. This advantage is crucial for the systems with a huge configuration space, first of all for deformed nuclei. SRPA takes self-consistently into account the contributions of both time-even and time-odd Skyrme terms as well as of the Coulomb force and pairing. The method is implemented to description of isovector E1 and isoscalar E2 giant resonances in a representative set of deformed nuclei: 154 Sm, 238 U, and 254 No. Four different Skyrme parameterizations (SkT6, SkM*, SLy6, and SkI3) are employed to explore dependence of the strength distributions on some basic characteristics of the Skyrme functional and nuclear matter. In particular, we discuss the role of isoscalar and isovector effective masses and their relation to time-odd contributions. High sensitivity of the right flank of E1 resonance to different Skyrme forces and the related artificial structure effects are analyzed.

Testing Skyrme energy-density functionals with the quasiparticle random-phase approximation in low-lying vibrational states of rare-earth nuclei

“…Since calculation A uses a larger pairing strength, it produces higher energies for low-lying quasiparticles than does calculation B. In the separable approximation [57,58], the forward QRPA amplitudes can be written as…”

Finite amplitude method applied to the giant dipole resonance in heavy rare-earth nuclei

“…Especially in the case where the spherical symmetry is broken, one often needs to employ an additional truncation on the two-quasiparticle model space in order to reduce the numerical cost [11,13,22,23]. Another approach to reduce the computational cost of the QRPA is the separable approximation for the residual interaction [15,[24][25][26]. Such a truncation or approximation, however, may invoke spurious excitations due to the broken self-consistency between the Hartree-Fock-Bogoliubov (HFB) ground state and the QRPA solution.…”

Skyrme RPA description ofγ-vibrational states in rare-earth nuclei

“…The calculations have been performed within the separable QRPA [15] based on the Skyrme functional [1]. The method is fully self-consistent since i) both the mean field and residual interaction are obtained from the same Skyrme functional, ii) the residual interaction includes all terms of the functional as well as the Coulomb direct and exchange terms.…”