Unified ab initio approach to bound and unbound states: no-core shell model with continuum and its application to 7He

Abstract

We introduce a unified approach to nuclear bound and continuum states based on the coupling of the no-core shell model (NCSM), a bound-state technique, with the no-core shell model/resonating group method (NCSM/RGM), a nuclear scattering technique. This new ab initio method, no-core shell model with continuum (NCSMC), leads to convergence properties superior to either NCSM or NCSM/RGM while providing a balanced approach to different classes of states. In the NCSMC, the ansatz for the many-nucleon wave function includes: i) a square-integrable A-nucleon component expanded in a complete harmonic oscillator basis; ii) a binary-cluster component with asymptotic boundary conditions that can properly describe weakly-bound states, resonances and scattering; and, in principle, iii) a three-cluster component suitable for the description of, e.g., Borromean halo nuclei and reactions with final three-body states. The Schroedinger equation is transformed into a system of coupled-channel integral-differential equations that we solve using a modified microscopic R-matrix formalism within a Lagrange mesh basis. We demonstrate the usefulness of the approach by investigating the unbound 7He nucleus.

16 pages, 10 figures

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• Chiral effective field theory and nuclear forces
• Similarity Renormalization Group for Nucleon-Nucleon Interactions
• Recent developments in no-core shell-model calculations
• Structure of A=10-13 nuclei with two- plus three-nucleon interactions from chiral effective field theory
• Ab Initio Many-Body Calculations of n-3H, n-4He, p-{3,4}He, and n-10Be Scattering
• Evolution of Nuclear Many-Body Forces with the Similarity Renormalization Group
• Quantum Monte Carlo calculations of neutron-alpha scattering
• Medium-mass nuclei from chiral nucleon-nucleon interactions
• Nuclear Structure in the Framework of the Unitary Correlation Operator Method
• Evolving Nuclear Many-Body Forces with the Similarity Renormalization Group
• Complex coupled-cluster approach to an ab-initio description of open quantum systems
• Unitary Correlation Operator Method and Similarity Renormalization Group: Connections and Differences
• Elastic proton scattering of medium mass nuclei from coupled-cluster theory
• Resonances of 7He in the complex scaling method

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