Microscopic self-energy calculations and dispersive optical-model potentials

Waldecker, S. J.; Barbieri, C.; Dickhoff, W. H.

doi:10.1103/physrevc.84.034616

Cited by 58 publications

(109 citation statements)

References 47 publications

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“…While this step allows the interpretation of the optical potential as representing the nucleon self-energy, it was also shown that observables like the nuclear charge density cannot be described in detail. By analyzing theoretically calculated self-energies for Ca isotopes which include long-range [23] and short-range correlations [24], it was possible to clarify the importance of representing the imaginary part of the optical potential also in terms of non-local ingredients. These insights have recently led to an extension of the dispersive optical model formalism to explicitly include non-locality [25,26] in the real and imaginary part of the self-energy specifically for the 40 Ca nucleus.…”

Section: Introductionmentioning

confidence: 99%

Effects of nonlocal potentials on(p,d)transfer reactions

et al. 2015

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Background: Although local phenomenological optical potentials have been standardly used to interpret nuclear reactions, recent studies suggest the effects of non-locality should not be neglected. Purpose: In this work we investigate the effects of non-locality in (p, d) transfer reactions using non-local optical potentials. We compare results obtained with the dispersive optical model to those obtained using the Perey-Buck interaction. Method: We solved the scattering and bound-state equations for the non-local version of the dispersive optical model. Then, using the distorted wave Born approximation, we calculate the transfer cross section for (p, d) on 40 Ca at Ep=20, 35 and 50 MeV. Results: The inclusion of non-locality in the bound state has a larger effect than on the scattering states. The overall effect on the transfer cross section is very significant. We found an increase due to non-locality in the transfer cross section of ≈ 30 − 50% when using the Perey-Buck interaction and ≈ 15 − 50% when using the dispersive optical potential. Conclusions: Although the details of the non-local interaction can change the magnitude of the effects, our study shows that qualitatively the results obtained using the dispersive optical potential and the Perey-Buck interaction are consistent, in both cases the transfer cross sections are significantly increased.

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Section: Introductionmentioning

confidence: 99%

Effects of nonlocal potentials on(p,d)transfer reactions

et al. 2015

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“…Ab initio many-body methods based on coupled cluster (CC) [1][2][3][4][5][6][7][8][9][10], self-consistent Dyson-Green's function (SCDyGF) [11][12][13][14][15] and in-medium similarity renormalization group (IMSRG) [16,17] techniques have been intensively developed in the last ten years to address nuclei up to mass A ∼ 130 [18]. However, these important developments have been limited until recently to doubly closed-(sub)shell nuclei plus those accessible via the addition and removal of one or two nucleons.…”

Section: Introductionmentioning

confidence: 99%

Ab initioBogoliubov coupled cluster theory for open-shell nuclei

et al. 2015

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Background: Ab initio many-body methods have been developed over the past ten years to address closed-shell nuclei up to mass A ∼ 130 on the basis of realistic two-and three-nucleon interactions. A current frontier relates to the extension of those many-body methods to the description of open-shell nuclei.Purpose: Several routes to address open-shell nuclei are currently under investigation, including ideas which exploit spontaneous symmetry breaking. Singly open-shell nuclei can be efficiently described via the sole breaking of U (1) gauge symmetry associated with particle-number conservation, as a way to account for their superfluid character. While this route was recently followed within the framework of self-consistent Green's function theory, the goal of the present work is to formulate a similar extension within the framework of coupled cluster theory.Methods: We formulate and apply Bogoliubov coupled cluster (BCC) theory, which consists of representing the exact ground-state wavefunction of the system as the exponential of a quasiparticle excitation cluster operator acting on a Bogoliubov reference state. Equations for the ground-state energy and the cluster amplitudes are derived at the singles and doubles level (BCCSD) both algebraically and diagrammatically. The formalism includes three-nucleon forces at the normal-ordered two-body level. The first BCCSD code is implemented in m-scheme, which will permit the treatment of doubly open-shell nuclei via the further breaking of SU (2) symmetry associated with angular momentum conservation.Results: Proof-of-principle calculations in an Nmax = 6 spherical harmonic oscillator basis are performed for 16,18,20 O, 18 Ne, and 20 Mg in the BCCD approximation with a chiral two-nucleon interaction, comparing to results obtained in standard coupled cluster theory when applicable. The breaking of U (1) symmetry is monitored by computing the variance associated with the particle-number operator. Conclusions:The newly developed many-body formalism increases the potential span of ab initio calculations based on single-reference coupled cluster techniques tremendously, i.e. potentially to reach several hundred additional mid-mass nuclei. The new formalism offers a wealth of potential applications and further extensions dedicated to the description of ground-and excited-states of open-shell nuclei. Short-term goals include the implementation of three-nucleon forces at the normal-ordered two-body level. Mid-term extensions include the approximate treatment of triple corrections and the development of the equation-of-motion methodology to treat both excited states and odd nuclei. Long-term extensions include exact restoration of U (1) and SU (2) symmetries.

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“…[15]. The introduction of nonlocality in the imaginary part of the self-energy is well-founded theoretically both for long-range correlations [18] as well as short-range ones [19]. Its implied ℓ-dependence is essential in reproducing the correct particle number for protons and neutrons.…”

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“…[18,19], we allow for different nonlocalities above and below the Fermi energy, otherwise the symmetry around this energy is essentially maintained by the fit. The values of the nonlocality parameters β appear reasonable and range from 0.64 fm above to 0.81 fm below the Fermi energy for volume absorption.…”

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Forging the Link between Nuclear Reactions and Nuclear Structure

et al. 2014

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A comprehensive description of all single-particle properties associated with the nucleus 40 Ca is generated by employing a nonlocal dispersive optical potential capable of simultaneously reproducing all relevant data above and below the Fermi energy. The introduction of nonlocality in the absorptive potentials yields equivalent elastic differential cross sections as compared to local versions but changes the absorption profile as a function of angular momentum suggesting important consequences for the analysis of nuclear reactions. Below the Fermi energy, nonlocality is essential to allow for an accurate representation of particle number and the nuclear charge density. Spectral properties implied by (e, e ′ p) and (p, 2p) reactions are correctly incorporated, including the energy distribution of about 10% high-momentum nucleons, as experimentally determined by data from Jefferson Lab. These high-momentum nucleons provide a substantial contribution to the energy of the ground state, indicating a residual attractive contribution from higher-body interactions for 40 Ca of about 0.64 MeV/A.PACS numbers: 21.10. Pc,24.10.Ht,11.55.Fv The properties of a nucleon that is strongly influenced by the presence of other nucleons have traditionally been studied in separate energy domains. Positive energy nucleons are described by fitted optical potentials mostly in local form [1,2]. Bound nucleons have been analyzed in static potentials that lead to an independent-particle model modified by the interaction between valence nucleons as in traditional shell-model calculations [3,4]. The link between nuclear reactions and nuclear structure is provided by considering these potentials as representing different energy domains of one underlying nucleon self-energy. This idea was implemented in the dispersive optical model (DOM) by Mahaux and Sartor [5]. By employing dispersion relations, the method provides a critical link between the physics above and below the Fermi energy with both sides being influenced by the absorptive potentials on the other side.The DOM provides an ideal strategy to predict properties for exotic nuclei by utilizing extrapolations of these potentials towards the respective drip lines [6,7]. The main stumbling block so far has been the need to utilize the approximate expressions for the properties of nucleons below the Fermi energy that were developed by Mahaux and Sartor [5] to correct for the normalizationdistorting energy dependence of the Hartree-Fock (HF) potential. By restoring the proper treatment of nonlocality in the HF contribution, it was possible to overcome this problem [8] although the local treatment of the absorptive potentials yielded a poor description of the nuclear charge density and particle number.In the present work we have for the first time treated the nonlocality of these potentials for the nucleus 40 Ca with the aim to include all available data below the Fermi energy that can be linked to the nucleon single-particle propagator [9] while maintaining a correct description of the el...

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Microscopic self-energy calculations and dispersive optical-model potentials

Cited by 58 publications

References 47 publications

Effects of nonlocal potentials on(p,d)transfer reactions

Effects of nonlocal potentials on(p,d)transfer reactions

Ab initioBogoliubov coupled cluster theory for open-shell nuclei

Forging the Link between Nuclear Reactions and Nuclear Structure

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