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Ionel Stetcu

University of Arizona
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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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