Large-basis ab initio no-core shell model and its application to C-12 - art. no. 054311

We present the framework for the ab initio no-core nuclear shell model and apply it to obtain properties of C-12. We derive two-body effective interac tions microscopically for specific model spaces from the realistic CD-Bonn and the Argonne V8' nucleon-nucleon (NN) potentials. We then evaluate bindi ng energies, excitation spectra, radii, and electromagnetic transitions in the 0 (h) over bar Ohm, 2 (h) over bar Ohm, and 4 (h) over bar Ohm model sp aces for the positive-parity states and the 1 (h) over bar Ohm, 3 (h) over bar Ohm, and 5 (h) over bar Ohm model spaces for the negative-parity states . Dependence on the model-space size, on the harmonic-oscillator frequency, and on the type of the NN potential, used for the effective interaction de rivation, are studied. In addition, electromagnetic and weak neutral elasti c charge form factors are calculated in the impulse approximation. Sensitiv ity of the form-factor ratios to the strangeness one-body form-factor param eters and to the influence of isospin-symmetry violation is evaluated and d iscussed. Agreement between theory and experiment is favorable for many obs ervables, while others require yet larger model spaces and/or three-body fo rces. The limitations of the present results are easily understood by virtu e of the trends established and previous phenomenological results.