Ionel Stetcu

University of Arizona

The ab-initio no core shell model: theory and applications

The ab initio no-core shell model (NCSM) is a powerful many-body technique, which provides bound-state solutions to the Schrodinger equation for A interacting nucleons in a restricted space, starting from realistic nucleon-nucleon interactions that accurately fit the experimental phaseshifts. The approach involves the use of a unitary transformation to obtain effective interactions in a restricted model space, which allows a many-body calculation by means of large scale diagonalization. New approaches will allow in the near future a more consistent treatment of both structure and reactions within the ab initio NCSM. I will discuss recent developments in the NCSM, including the unitary transformation approach to the theory of effective operators as well as the first Lorentz integral transform implementation in the NCSM framework. Finally, I will present a new approach, based on effective field theory, to the derivation of effective operators directly in a truncated harmonic oscillator basis, appropriate for NCSM calculations. This approach makes possible the obtaining of reliable effective interactions for heavier nuclei, relevant to astrophysics, in model spaces that should still be numerically tractable. In this talk, I will concentrate on the description of two-body scattering observables in a restricted harmonic oscillator basis.

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