Chiral two- and three-nucleon forces along medium-mass isotope chains

Abstract

Ab initio calculations have shown that chiral two-and three-nucleon interactions correctly reproduce binding energy systematics and neutron drip lines of oxygen and nearby isotopes. Exploiting the novel Gorkov-Green's function approach applicable to genuinely open-shell nuclei, we present the first ab initio investigation of Ar, K, Ca, Sc, and Ti isotopic chains. In doing so, stringent tests of internucleon interaction models are provided in the medium-mass region of the nuclear chart. Leading chiral three-nucleon interactions are shown to be mandatory to reproduce the trend of binding energies throughout these chains and to obtain a good description of two-neutron separation energies. At the same time, nuclei in this mass region are systematically overbound by about 40 MeV. While the fundamental N = 20 and 28 magic numbers do emerge from basic internucleon interactions, the former is shown to be significantly overestimated, which points to deficiencies of state-of-the-art chiral potentials. The present results demonstrate that ab initio many-body calculations can now access entire medium-mass isotopic chains including degenerate open-shell nuclei and provide a critical testing ground for modern theories of nuclear interactions.

Chiral three-nucleon forces and the evolution of correlations along the oxygen isotopic chain

“…Ref. [22] pointed out that the experimental gaps between the sd and pf shells are over estimated for the Ca and neighbouring isotopic chains. To investigate the behaviour in the present case, we consider the separations between the dominant 5/2 + and 1/2 − fragments that is representative of the gap between the p and sd shells.…”

“…at the ADC(2) level]. Although this does not guarantee the best precision for quasiparticle energies [49], it still yields proper predictions for the trend of binding energies [22].…”

“…In general, we find values evenly spread between 70% and 90% of the independent particle model. The smaller values of SFs are obtained at low separation energies and involve transitions to/from 14,22,24 O. These isotopes present reduced particle-hole neutron gaps and therefore allow for stronger correlations at the Fermi surface.…”

“…These allow to fully exploit modern chiral interactions with two-nucleon (NN) and 3NFs evolved through SRG techniques [28]. Moreover, open shell nuclei have become arXiv:1412.0491v2 [nucl-th] 19 Jun 2015 accessible through a Gorkov extension of the SCGF formalism [22,29,30], multi-reference IM-SRG [18,23] and Bogoliubov coupled cluster (BCC) [31]. These ab initio studies have mainly focussed on ground state properties, such as total binding energies and two-nucleon separation energies.…”

In-medium similarity renormalization group for closed and open-shell nuclei

“…Truncations in the SRG flow equation cause a violation of unitarity that manifests as a (residual) dependence of many-body results on λ. By varying this parameter, the size of the missing contributions can be assessed (see, e.g., [33,55,57,61,91,[99][100][101][102]). State-of-the-art SRG evolutions of nuclear interactions are nowadays performed in the three-body system, using relative (Jacobi) harmonic oscillator [54,100,103], relative momentum plane wave [101], or momentum-space hypherspherical harmonics representations [104].…”