Quasiparticle time blocking approximation within the framework of generalized Green function formalism

Tselyaev, V.

doi:10.1103/physrevc.75.024306

Cited by 129 publications

(239 citation statements)

References 27 publications

(59 reference statements)

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“…The residual interaction for the (Q)RPA and QTBA calculations is derived as the second derivative of the Skyrme functional [38]. Although the QTBA model [4] was originally formulated in terms of the general basis, several simplifications are performed in our calculations. Namely, the QTBA approach is designed to use the BCSbased quasiparticle basis and we use the HFB approach to extract the quasiparticle characteristics and corresponding wave functions (i.e., the occupation numbers are treated as per the BCS approximation).…”

Section: A Methodsmentioning

confidence: 99%

“…The other feature of our calculation scheme is the so-called subtraction procedure [4,7] which should avoid a PC double counting from the effective interaction. This procedure is a direct continuation of the phenomenological refinement philosophy used in the first formulations of the ETFFS [3,47].…”

Section: A Methodsmentioning

confidence: 99%

“…This is one of the main reasons to use some additional procedures to exclude ghost states; in particular, the spurious isoscalar 1 − state. This is achieved through a specific fit of the force parameters [5,6,8], the use of the so-called subtraction procedure in the QTBA model [4], or of the so-called forced consistency method [11,12]. Nevertheless, accounting for PC and self-consistency increases, beyond any doubt, the quality of the microscopic nuclear theory and is absolutely necessary to simultaneously describe the structure of ground and excited states for unstable nuclei.…”

Section: Introductionmentioning

confidence: 99%

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Self-consistent calculations of the strength function and radiative neutron capture cross section for stable and unstable tin isotopes

Авдеенков

Goriely²,

Kamerdzhiev

et al. 2011

Phys. Rev. C

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The E1 strength function for 15 stable and unstable Sn even-even isotopes from A = 100 to A = 176 are calculated using a self-consistent microscopic theory which, in addition to the standard (quasiparticle) randomphase approximation [(Q)RPA] approach, takes into account phonon coupling and the single-particle continuum (by means of the discretization procedure) with a cutoff of 100 MeV. Our analysis shows two distinct regions for which the integral characteristics of both the giant and pygmy resonances behave rather differently. For neutron-rich nuclei, starting from 132 Sn, we obtain a giant E1 resonance which significantly deviates from the widely used systematics extrapolated from experimental data in the β-stability valley. We show that the inclusion of phonon coupling is necessary for a proper description of the low-energy pygmy resonances and the corresponding transition densities for A < 132 nuclei, while in the A > 132 region the influence of phonon coupling is significantly smaller. The radiative neutron capture cross sections leading to the stable 124 Sn and unstable 132 Sn and 150 Sn nuclei are calculated with both the (Q)RPA and the beyond-(Q)RPA strength functions and shown to be sensitive to both the predicted low-lying strength and the phonon-coupling contribution. The comparison with the widely used phenomenological generalized Lorentzian approach shows considerable differences both for the strength function and the radiative neutron capture cross section. In particular, for the neutron-rich 150 Sn, the reaction cross section is found to be increased by a factor greater than 20. We conclude that the present approach may provide a complete and coherent description of the γ -ray-strength function for astrophysics applications. In particular, such calculations are highly recommended for a reliable estimate of the electromagnetic properties of exotic nuclei.

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Section: A Methodsmentioning

confidence: 99%

Section: A Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Self-consistent calculations of the strength function and radiative neutron capture cross section for stable and unstable tin isotopes

Авдеенков

Goriely²,

Kamerdzhiev

et al. 2011

Phys. Rev. C

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“…The coupling of particles and phonons has also been derived from Nuclear Field Theory (NFT) and its extensions [26,27,28]. Many aspects of the coupling between the quasi-particles and the collective vibrations have been investigated with these techniques [29,30,31,32,33,34,35,36,37,38] as well as with other kinds of approaches beyond RPA [39,40] over the years.…”

Section: Introductionmentioning

confidence: 99%

Particle-vibration coupling within covariant density functional theory

2007

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Covariant density functional theory, which has so far been applied only within the framework of static and time dependent mean field theory is extended to include Particle-Vibration Coupling (PVC) in a consistent way. Starting from a conventional energy functional we calculate the lowlying collective vibrations in Relativistic Random Phase Approximation (RRPA) and construct an energy dependent self-energy for the Dyson equation. The resulting Bethe-Salpeter equation in the particle-hole (ph) channel is solved in the Time Blocking Approximation (TBA). No additional parameters are used and double counting is avoided by a proper subtraction method. The same energy functional, i.e. the same set of coupling constants, generates the Dirac-Hartree singleparticle spectrum, the static part of the residual ph-interaction and the particle-phonon coupling vertices. Therefore a fully consistent description of nuclear excited states is developed. This method is applied for an investigation of damping phenomena in the spherical nuclei with closed shells 208 Pb and 132 Sn. Since the phonon coupling terms enrich the RRPA spectrum with a multitude of ph⊗phonon components a noticeable fragmentation of the giant resonances is found, which is in full agreement with experimental data and with results of the semi-phenomenological non-relativistic approach.

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“…In particular, the Extended Theory of Finite Fermi Systems (ETFFS) [1] includes both PC and the single-particle continuum, the latter being absolutely necessary for nuclei with the nucleon separation energy near zero. This approach has been recently generalized to include pairing in the quasiparticle time-blocking approximation [2], (ETFFS(QTBA)). This and other approaches developed with the PC have been supplemented with consideration of the self-consistency between the mean field and the effective interaction [3,4,5].…”

Section: Introductionmentioning

confidence: 99%

Impact of the Phonon Coupling on the Dipole Strength and Radiative NeutronCapture

Авдеенков¹,

Goriely²,

Kamerdzhiev³

2011

J. Korean Phy. Soc.

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The E1 strength functions and radiative capture cross sections for several compound Sn isotopes, including unstable 132 Sn and 150 Sn, have been calculated using the self-consistent microscopic theory. In addition to the standard RPA or QRPA approaches, the method includes the quasiparticle-phonon coupling and the single-particle continuum. The results obtained show that the phonon contribution significantly affects the pygmy dipole resonance, which is of particular relevance for a proper description of the radiative neutron capture. The impact of the phonon coupling on the pygmy dipole resonance and the radiative neutron capture cross sections increases with the (N − Z) difference. For example, in the (0-10) MeV interval the full theory gives 17% of the energy-weighted sum rule for 150 Sn and 2.8% for 124 Sn, whereas the continuum QRPA approach gives 5.1% and 1.7%, respectively. These results indicate the importance the self-consistent calculation can have, especially when applied to neutron-rich nuclei of astrophysical interest. The comparison with the widely-used phenomenological Generalized Lorentzian approach shows that the (Q)RPA approach gives an increase in the neutron capture cross section by a factor of 2 for 132 Sn and a factor of 10 for 150 Sn and that the inclusion of the phonon coupling still increases these cross sections even furhter, by a factor of 2-3.

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Quasiparticle time blocking approximation within the framework of generalized Green function formalism

Cited by 129 publications

References 27 publications

Self-consistent calculations of the strength function and radiative neutron capture cross section for stable and unstable tin isotopes

Self-consistent calculations of the strength function and radiative neutron capture cross section for stable and unstable tin isotopes

Particle-vibration coupling within covariant density functional theory

Impact of the Phonon Coupling on the Dipole Strength and Radiative NeutronCapture

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