Highly deformed modes in the ab initio symplectic no-core shell model
We show that highly deformed modes essential for nuclear dynamics modeling can readily be included in the symplectic no-core shell model (Sp-NCSM) space. In particular, a prescription for constructing general deformed k-particle-k-hole (kp-kh) translationally invariant symplectic starting state configurations and symplectic excitations thereof in a fermion-based spherical harmonic oscillator basis is presented. This prescription is used to build the symplectic excitations over all possible as well as the most deformed configurations in 12C and 16O. The extent to which these configurations enter into low-lying states for these nuclei calculated within the framework of the no-core shell model with a realistic microscopic interaction is then determined. Typically, the addition of these and representations to the leading results grow the overall overlap with the no-core-shell-model eigenstates by 5-10% for a total of 85-90%. And most importantly, even with the addition of these higher-order particle-hole configurations, the dimensionality of the symplectic subspace constitutes a very small fraction of the conventional full no-core shell model space, which reaffirms the relevance of the Sp-NCSM scheme. © 2008 IOP Publishing Ltd.