BCS-Pairing and Nuclear Vibrations

Matsuyanagi, Kenichi; Hinohara, Nobuo; Sato, Koichi

doi:10.1142/9789814412490_0009

Cited by 8 publications

(9 citation statements)

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“…Low-frequency quadrupole vibrations of the nucleus may be regarded as collective surface excitations of a finite superfluid system. Accordingly, pairing correlations and varying shell structure of the self-consistent mean field play essential roles in their emergence ( Åberg et al, 1990;Bender et al, 2003;Bohr and Mottelson, 1975;Matsuyanagi et al, 2013;Rowe and Wood, 2010). For nuclei in the transitional region from spherical to deformed, amplitudes of quantum shape fluctuation remarkably increase.…”

Section: Characteristics Of Quadrupole Excitation Spectra In Low-lyin...mentioning

confidence: 99%

Time-dependent density-functional description of nuclear dynamics

et al. 2016

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We present the basic concepts and recent developments in the time-dependent density functional theory (TDDFT) for describing nuclear dynamics at low energy. The symmetry breaking is inherent in nuclear energy density functionals (EDFs), which provides a practical description of important correlations at the ground state. Properties of elementary modes of excitation are strongly influenced by the symmetry breaking and can be studied with TDDFT. In particular, a number of recent developments in the linear response calculation have demonstrated their usefulness in description of collective modes of excitation in nuclei. Unrestricted real-time calculations have also become available in recent years, with new developments for quantitative description of nuclear collision phenomena. There are, however, limitations in the real-time approach; for instance, it cannot describe the many-body quantum tunneling. Thus, we treat the quantum fluctuations associated with slow collective motions assuming that time evolution of densities are determined by a few collective coordinates and momenta. The concept of collective submanifold is introduced in the phase space associated with the TDDFT and used to quantize the collective dynamics. Selected applications are presented to demonstrate the usefulness and quality of the new approaches. Finally, conceptual differences between nuclear and electronic TDDFT are discussed, with some recent applications to studies of electron dynamics in the linear response and under a strong laser field.

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Section: Characteristics Of Quadrupole Excitation Spectra In Low-lyin...mentioning

confidence: 99%

Time-dependent density-functional description of nuclear dynamics

et al. 2016

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“…Pairing correlations are essential for describing lowenergy vibrational modes of excitation [24] and are a key to understanding the collective nature. Therefore, in this arXiv:2105.03128v1 [nucl-th] 7 May 2021 article, I am going to investigate the role of the pairing correlations in both the static and dynamic aspects, as done in the studies in exotic nuclei in the neutron-rich region [25][26][27].…”

Section: Introductionmentioning

confidence: 99%

Pairing and nonaxial-shape correlations in N=150 isotones

Yoshida

2021

Phys. Rev. C

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Background: Rotational bands have been measured around 250 Fm associated with strong deformed-shell closures. The K π = 2 − excited band emerges systematically in N = 150 isotones raging from plutonium to nobelium with even-Z numbers, and a sharp drop in energies was observed in californium.Purpose: I attempt to uncover the microscopic mechanism for the appearance of such a low-energy 2 − state in 248 Cf. Furthermore, I investigate the possible occurrence of the low-energy K π = 2 + state, the γ vibration, to elucidate the mechanism that prefers the simultaneous breaking of the reflection and axial symmetry to the breaking of the axial symmetry alone in this mass region.Method: I employ a nuclear energy-density functional (EDF) method: the Skyrme-Kohn-Sham-Bogoliubov and the quasiparticle random-phase approximation are used to describe the ground state and the transition to excited states. Results:The Skyrme-type SkM* and SLy4 functionals reproduce the fall in energy but not the absolute value of the K π = 2 − state at Z = 98 where the proton two-quasiparticle excitation [633]7/2 ⊗ [521]3/2 plays a decisive role for the peculiar isotonic dependence. I find interweaving roles by the pairing correlation of protons and the deformed-shell closure at Z = 98. The SkM* model predicts the K π = 2 − state appears lower in energy in 246 Cf than in 248 Cf as the Fermi level of neutrons is located in between the [622]5/2 and the [734]9/2 orbitals. Except for 250 Fm in the SkM* calculation, the K π = 2 + state is predicted to appear higher in energy than the K π = 2 − state because the quasiproton [521]1/2 orbital is located above the [633]7/2 orbital. Conclusions:A systematic study of low-lying collective states in heavy actinide nuclei provides a rigorous testing ground for microscopic nuclear models. The present paper shows a need for improvements in the EDFs to describe pairing correlations and shell structures in heavy nuclei, that are indispensable in predicting the heaviest nuclei.

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“…There are also dynamical effects of pairing correlations seen in the moment of inertia associated with nuclear rotation and large amplitude collective motion [3,4,5]. The Hartree-Fock (HF)+BCS method and HartreeFock-Bogoliubov (HFB) method have been commonly used to study the ground state properties of superfluid nuclei in a broad mass region [6,7,8,9].…”

Section: Introductionmentioning

confidence: 99%

Role of T=0 pairing in Gamow–Teller states in N=Z nuclei

et al. 2013

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Gamow-Teller (GT) states in N=Z nuclei with the mass number A from 48 to 64 are studied by using Hartree-Fock-Bogoliubov + quasi-particle random phase approximation (HFB+QRPA) with Skyrme interactions. The isoscalar spin-triplet (T=0,S=1) pairing interaction is taken into account in QRPA calculations. It is found in the context of SU(4) symmetry in the spin-isospin space that the GT strength of lower energy excitations is largely enhanced by the T=0 pairing interaction which works cooperatively with the T=1 pairing interaction in the ground state. A two-peaked structure observed recently in (p, n) reaction on 56 Ni can be considered as a manifestation of the role of T=0 pairing in the GT collective states. Keywords:Gamow Teller states, T=0 pairing interaction, SU(4) supermultipletThe most prominent evidence of pairing correlation in nuclei is found in the odd-even staggering in binding energies and the gap in the excitation spectrum of even-even nuclei in contrast to the compressed quasi-particle spectrum in odd-A nuclei [1,2,3]. There are also dynamical effects of pairing correlations seen in the moment of inertia associated with nuclear rotation and large amplitude collective motion [3,4,5]. The Hartree-Fock (HF)+BCS method and HartreeFock-Bogoliubov (HFB) method have been commonly used to study the ground state properties of superfluid nuclei in a broad mass region [6,7,8,9]. For the study of excited spectra, quasiparticle random phase approximation (QRPA) has often been adopted as a basic method [10,11,12,13].The strong attraction between nucleons is the basic ingredient for the pairing correlations. So far, the pairing interactions of like-nucleons with the isovector spin-singlet (T=1, S=0) channel has been mainly discussed. In fact, the attraction between protons and neutrons is even stronger in the isoscalar spin-triplet (T=0, S=1) channel [14], which gives rise to the deuteron bound state. However the role of T=0 pairing is limited in nuclei because of large imbalance between neutron and proton numbers, and also the two-body spin-orbit interaction which breaks the S=1 pair more effectively than the S=0 pair [4,15,16]. Nevertheless, the isoscalar pairing causes extra binding energies in nuclei with N=Z and has been considered as one of the origins of the Wigner energy [17].Gamow-Teller (GT) states have been studied both experimentally and theoretically intensively in the last three decades. Many interesting nuclear structure information has been reEmail address: sagawa@u-aizu.ac.jp (H. Sagawa) vealed by these studies, for example, the quenching of sum rule strength [18] and the role of GT strength in the astrophysical processes such as neutrino-nucleus reactions [19]. Because of recent development of modern radioactive beam accelerator, it becomes feasible to observe GT states in exotic nuclei near the proton and neutron drip lines. Recently, the GT transition strength was studied in a N=Z nucleus 56 Ni which has an important impact on late stellar evolution through electron capture and β deca...

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BCS-Pairing and Nuclear Vibrations

Cited by 8 publications

References 42 publications

Time-dependent density-functional description of nuclear dynamics

Time-dependent density-functional description of nuclear dynamics

Pairing and nonaxial-shape correlations in N=150 isotones

Role of T=0 pairing in Gamow–Teller states in N=Z nuclei

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