Soft modes in the proton–neutron pairing channel as precursors of deuteron condensate in N=Z nuclei

Литвинова, Елена; Robin, Caroline; Егорова, И. А.

doi:10.1016/j.physletb.2017.11.026

Cited by 15 publications

(15 citation statements)

References 59 publications

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“…At zero temperature the inclusion of the PVC effects in the time blocking approximation leads to a consistent refinement of the calculated spectra in both neutral [10,16,17,53,54,[70][71][72][73][74][75][76] and charge-exchange [67][68][69][77][78][79] channels, as compared to the (Q)RPA approaches, due to the spreading effects. In this work we adopt the Matsubara Green's function formalism for the finite-temperature generalization of the relativistic time blocking approximation (RTBA) [51].…”

Section: Introductionmentioning

confidence: 84%

Nuclear dipole response in the finite-temperature relativistic time-blocking approximation

Wibowo

Литвинова

2019

Phys. Rev. C

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Background:The radiative neutron capture reaction rates of the r-process nucleosynthesis are immensely affected by the microscopic structure of the low-energy spectra of compound nuclei. The relativistic (quasiparticle) time blocking approximation (R(Q)TBA) has successfully provided a good description of the lowenergy strength, in particular, the strength associated with pygmy dipole resonance, describing transitions from and to the nuclear ground state. The finite-temperature generalization of this method is designed for thermally excited compound nuclei and has the potential to enrich the fine structure of the dipole strength, especially in the low-energy region. Purpose: To formulate the thermal extension of RTBA, i.e., finite-temperature relativistic time blocking approximation (FT-RTBA) for the nuclear response, and to implement it numerically for calculations of the dipole strength in medium-light and medium-heavy nuclei. Methods: The FT-RTBA equations are derived using the Matsubara Green's function formalism. We show that with the help of a temperature-dependent projection operator on the subspace of the imaginary time it is possible to reduce the Bethe-Salpeter equation for the nuclear response function to a single frequency variable equation also at finite temperatures. The approach is implemented self-consistently in the framework of quantum hadrodynamics and keeps the ability of connecting the high-energy scale of heavy mesons and the low-energy domain of nuclear medium polarization effects in a parameter-free way. Results: The method was applied to the medium-light 48 Ca, 68 Ni and to the medium-heavy 100,120,132 Sn nuclei. The excitation energies E * of the considered compound nuclei were calculated and found to increase quickly starting from temperatures 0.5 ≤ T ≤ 1.0 MeV. The nucleonic single-particle energies and occupancies change accordingly because of the increasing diffuseness of the Fermi-Dirac distribution with the temperature increase. The dipole response of these nuclei was computed in the FT-RTBA and compared to the finite-temperature relativistic RPA (FT-RRPA). It was found that the giant dipole resonance (GDR) undergoes additional fragmentation (i) due to the thermal unblocking of the transitions between single-particle states located on the same side of the Fermi surface and (ii) because of the general reinforcement of the particle-vibration coupling (PVC) with the temperature growth. The low-energy part of the dipole strength distribution is moderately enhanced at temperatures T ≤ 4.0 MeV and increases dramatically above this temperature range. The width of the strength distribution grows rapidly with temperature at T ≥ 1.0 MeV. The energy-weighted sum rule (EWSR) in a wide finite energy interval remains nearly flat as the temperature increases. The traditional view of the PDR as an oscillation of the weakly bound neutron excess against the isospin-saturated core is nearly maintained up to the temperature T = 5.0 MeV and changes to the GDR-like pattern above this temperature. The col...

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Section: Introductionmentioning

confidence: 84%

Nuclear dipole response in the finite-temperature relativistic time-blocking approximation

Wibowo

Литвинова

2019

Phys. Rev. C

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“…Since D 22 can be obtained in the same equation (B10) by simply replacing ω to −ω, we will not distinguish these two matrix explicitly and simply write p 1 h 1 |D(ω)|p 2 h 2 λ nL . In the end, the full spreading term (34) in the jj-coupled form can be written as…”

Section: Acknowledgmentsmentioning

confidence: 99%

“…with W ↓ p ′ h ′ ,ph (ω) given in Eq. (34). When the PVC equation is solved in the RPA phonon basis, one can transform this matrix to the phonon representation by…”

Section: Appendix A: Effective Hamiltonian In Q1 Subspacementioning

confidence: 99%

“…Two main effects were identified to contribute to the width, the escape of a nucleon from the nucleus (escape width) and the spreading of the excitation energy into more complicated configurations (spreading width) [18]. Different efforts have been made to take into account these effects, for example: continuum RPA [19,20]; second RPA (SRPA) [21][22][23][24][25]; quasiparticlephonon model [26][27][28][29] quasiparticle-phonon model based on time-blocking approximation (TBA) [30][31][32]; TBA in the relativistic framework [33][34][35].…”

Section: Introductionmentioning

confidence: 99%

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Particle-vibration coupling for giant resonances beyond the diagonal approximation

Shen¹,

Roca-Maza²

2020

Phys. Rev. C

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A fully self-consistent particle-vibration coupling (PVC) model is presented. The main novelty stands in releasing the so-called diagonal approximation that neglects completely the interaction between the doorway states. As applications, isoscalar giant monopole, dipole, and quadrupole resonances in 16 O are investigated based on the use of Skyrme functionals. The diagonal approximation is found to clearly impact on the strength distribution of the giant quadrupole resonance, and the description of the experimental data is improved when we perform the full calculation. The impact of the diagonal approximation is analyzed in detail, especially its effect on the eigenenergies and the induced coupling between neutron and proton particle-hole configurations. The latter is a direct and physically sound effect of the improvement on our formalism. The importance of using self-consistently the full effective interaction in the PVC vertex, and the effect of its renormalization via the subtraction method are also discussed. For completness, we also analyze the dependence on the Skyrme parameterization in our results.PACS numbers:

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“…The calculations are based on the NL3 meson-exchange interaction [45] and free-space pion-nucleon coupling with the zero-range Landau-Migdal term, see Ref. [44] for more details. The pn-pp-RRPA results with various values of the strength of the repulsive Landau-Migdal interaction are shown by blue, green and orange curves.…”

Section: Pos(inpc2016)045mentioning

confidence: 99%

Effects Of Meson-nucleon Dynamics In A Relativistic Approach To Medium-mass Nuclei

Литвинова¹,

Robin²

2017

Proceedings of the 26th International Nuclear Physics Conference — PoS(INPC2016)

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Recent developments in the relativistic nuclear field theory (RNFT) are reviewed. Based on the covariant meson-nucleon Lagrangian of quantum hadrodynamics, RNFT connects consistently the high-energy scale of heavy mesons, medium-energy range of pion and the low-energy domain of emergent collective vibrations (phonons) in a parameter-free way. Mesons and phonons build up the effective interaction in various channels, in particular, the phonon-exchange part takes care of the retardation effects, which are of great importance for the fragmentation of single-particle states, spreading of collective giant resonances and soft modes, quenching and beta-decay rates with significant consequences for astrophysics and for the theory of weak processes in nuclei. As examples, the recently discovered impact of isospin dynamics on the nuclear shell structure and the isospin-flip pairing vibrations are discussed.

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Soft modes in the proton–neutron pairing channel as precursors of deuteron condensate in N=Z nuclei

Cited by 15 publications

References 59 publications

Nuclear dipole response in the finite-temperature relativistic time-blocking approximation

Nuclear dipole response in the finite-temperature relativistic time-blocking approximation

Particle-vibration coupling for giant resonances beyond the diagonal approximation

Effects Of Meson-nucleon Dynamics In A Relativistic Approach To Medium-mass Nuclei

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