Report

What are we doing? What are we doing? Large-scale ab initio No-core Shell Model calculations What are we doing? Large-scale ab initio No-core Shell Model calculations + new realistic NN interaction JISP Ab initio: Ab initio: • No model assumptions (shell model with inert core, cluster model, etc., are not ab initio) Ab initio: • No model assumptions (shell model with inert core, cluster model, etc., are not ab initio) • Ab initio approaches: • Faddeev (A 4) • hyperspherical (A 6) • • • Green function’s Monte Carlo (A 13) no-core shell model (A < 20) coupled-cluster approach (around closed shells) Modern NN interaction models: Modern NN interaction models: • Realistic (phenomenological) meson-exchange NN potentials (Nijmegen, Bonn, Argonne) + NNN phenomenological potentials Modern NN interaction models: • Realistic (phenomenological) meson-exchange NN potentials (Nijmegen, Bonn, Argonne) + NNN phenomenological potentials • EFT (ChPT) NN potentials + NNN EFT (ChPT) potentials Modern NN interaction models: • Realistic (phenomenological) meson-exchange NN potentials (Nijmegen, Bonn, Argonne) + NNN phenomenological potentials • EFT (ChPT) NN potentials + NNN EFT (ChPT) potentials • JISP16 NN interaction no NNN interaction fitted to light nuclei Why would be nice to avoid NNN forces? Role of NNN force? • W. Polyzou and W. Glöckle theorem (Few-body Syst. 9, 97 H=T+Vij H’=T+V’ij+Vijk, (1990)): where Vij and V’ij are phase-equivalent, H and H’ are isospectral. Hope: H’=T+V’ij+Vijk H=T+Vij with (approximately) isospectral H and H’ . JISP type interaction seems to be NN interaction minimizing NNN force. Without NNN force calculations are simpler, calculations are faster, larger model spaces become available; hence predictions are more reliable. JISP = J-matrix inverse scattering potential J-matrix formalism: scattering in the oscillator basis JISP NN interaction • NN interaction is a small matrix of the in the oscillator basis: 9ћΩ truncation, ћΩ = 40 MeV fast convergence of shell model calculations • Good description of NN data JISP16 properties • 1992 np data base (2514 data): χ2/datum = 1.03 • 1999 np data base (3058 data): χ2/datum = 1.05 PETs Ambiguity of JISP interaction • Any unitary transformation of NN Hamiltonian H generates a Phase-equivalent transformation (PET). • Simplest PETs with continuous parameters are used to fit properties of light nuclei in No-core Shell Model (NCSM) calculations. JISP NN interaction • A. M. Shirokov, A. I. Mazur, S. A. Zaytsev, J. P. Vary, T. A. Weber, Phys. Rev. C 70, 044005 (2004): A ≤ 4 • A. M. Shirokov, J. P. Vary, A. I. Mazur, S. A. Zaytsev, T. A. Weber, Phys. Lett. B 621, 96 (2005): A ≤ 6 — JISP6 • A. M. Shirokov, J. P. Vary, A. I. Mazur, T. A. Weber, Phys. Lett. B 644, 33 (2007): A ≤ 16 — JISP16 Modern NN interaction models: • Meson-exchange NN potentials (Nijmegen, Bonn, Argonne) and EFT (ChPT) NN potentials + NNN phenomenological or EFT (ChPT) potentials bad convergence; effective interaction is needed • JISP16 NN interaction good enough convergence with bare interaction Our initial approach From effective interactions to no-core full configuration calculations • Extrapolation: Egs(Nmax) = ae-bNmax + Egs(∞) • Works with bare interaction only (e.g., JISP16) • Example: P. Maris, J. P. Vary, A. M. Shirokov, Phys. Rev. C 79, 014308 (2009) Successful prediction: 14F • 1,990,061,078 basis states • each ħΩ point requires 2 to 3 hours on 7,626 quad-core compute nodes (30,504 processors in total) at the Jaguar supercomputer at ORNL Successful prediction: 14F spectrum • Deficiency of JISP16 revealed by NCFC extrapolations How it looked initially: How it looks now: Improved interaction JISP162010 • Obtained by a more accurate fit to nuclear data using NCFC Nuclear matter with JISP16 Nuclear matter • JISP162010 improves NM properties. • Strong dependence on high partial waves makes it possible to fit NM to phenomenological data without violating description of light nuclei. Conclusions • Ab initio NCFC approach based on NCSM is able to describe light nuclei with A < 20. • JISP16 provides a good description of NN data and binding energies, spectra, EM transitions in light nuclei, etc., without NNN forces. • An improved version JISP162010 providing a more accurate description of nuclei is available. Later this version will be additionally fitted to nuclear matter too. • Further development: description of other observables, e.g., rms radii in heavy enough nuclei, description of heavier nuclei, design of charge-dependent version of the interaction. Thank you!