Infrared extrapolations for atomic nuclei

Furnstahl, R. J.; Hagen, G.; Papenbrock, T.; Wendt, Kyle

doi:10.1088/0954-3899/42/3/034032

Cited by 58 publications

(78 citation statements)

References 36 publications

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“…In comparison to the converged energy of 16 O, -123.5(1) MeV, we observe 1.3 MeV overbinding from the extrapolation procedure. This is consistent with the results of [48] for N max = 6 [49], whereas extrapolations from N max = 8, 10, 12 do not lead to overbinding. Possible explanations for this imperfect extrapolation are insufficient decoupling of the center of mass due to the small model space, or a peculiarity of the CCSD calculation at N max = 6 [48].…”

Section: B Resultssupporting

confidence: 92%

“…In order to make predictions that are more accurate than 5%, we utilize the infrared (IR) extrapolation technique [47,48]. The oscillator basis truncation effectively imposes a Dirichlet boundary condition at a radius L in position space, approximated by…”

Section: B Resultsmentioning

confidence: 99%

“…where b = /(M ω) is the oscillator length and N eff is obtained by matching to the lowest eigenvalue of the squared momentum operator [48]. For 16 O, the values of N eff are included in Tab.…”

Section: B Resultsmentioning

confidence: 99%

“…For 16 O, the values of N eff are included in Tab. 1 of Furnstahl et al [48]. With the effective radius in position space, the IR extrapolation technique, originally derived for a single-particle degree of freedom but now implemented also for bound many-body systems, can be implemented via the expression [48] …”

Section: B Resultsmentioning

confidence: 99%

“…In fact, the NNLO opt cutoff is not sharp, so Λ UV must be sufficiently higher than Λ N N [48]. Erring on the side of caution, we fit Eq.…”

Section: B Resultsmentioning

confidence: 99%

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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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Section: B Resultssupporting

confidence: 92%

Section: B Resultsmentioning

confidence: 99%

Section: B Resultsmentioning

confidence: 99%

Section: B Resultsmentioning

confidence: 99%

“…In fact, the NNLO opt cutoff is not sharp, so Λ UV must be sufficiently higher than Λ N N [48]. Erring on the side of caution, we fit Eq.…”

Section: B Resultsmentioning

confidence: 99%

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Ab initioBogoliubov coupled cluster theory for open-shell nuclei

et al. 2015

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Natural orbital description of the halo nucleus 6He

et al. 2017

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Ab initio calculations of nuclei face the challenge of simultaneously describing strong short-range internucleon correlations and the long-range properties of weakly-bound halo nucleons. Natural orbitals, which diagonalize the one-body density matrix, provide a basis which is better matched to the physical structure of the many-body wave function. We demonstrate that the use of natural orbitals significantly improves convergence for ab initio no-core configuration interaction calculations of the neutron halo nucleus 6 He, relative to the traditional oscillator basis.

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Infrared extrapolations for atomic nuclei

Cited by 58 publications

References 36 publications

Ab initioBogoliubov coupled cluster theory for open-shell nuclei

Ab initioBogoliubov coupled cluster theory for open-shell nuclei

Natural orbital description of the halo nucleus 6He

Three-nucleon forces: Implementation and applications to atomic nuclei and dense matter

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