Morphing the shell model into an effective theory

We describe a strategy for attacking the canonical nuclear structure proble m-bound-state properties of a system of point nucleons interacting via a tw o-body potential-which involves an expansion in the number of particles sca ttering at high momenta, but is otherwise exact. The required self-consiste nt solutions of the Bloch-Horowitz equation for effective interactions and operators are obtained by an efficient Green's function method based on the Lanczos algorithm. We carry out this program for the simplest nuclei, d an d He-3, in order to explore the consequences of reformulating the shell mod el as a controlled effective theory.