Importance truncation for the symplectic no-core configuration interaction framework*

The \textit{ab initio} no-core configuration interaction (NCCI), or no-core shell model (NCSM), approach predicts properties of light nuclei from the underlying internucleon interaction. However, the dimension of the NCCI model space rapidly increases with the maximal number of allowed excitation oscillator quanta and the number of nucleons, which limits the convergence of calculated observables that can be achieved in practice. In the symplectic NCCI (SpNCCI) framework, the basis is organized according to the Sp(3,\textit{R}) symmetry giving us the opportunity to truncate the basis by symmetry properties. In this work we apply a truncation scheme based on the ideas of the importance-truncated NCSM (IT-NCSM), where the basis is truncated by an importance measure derived from first-order perturbation theory. We explore the effect of the importance truncation on the dimension of the SpNCCI model space and the convergence of calculated observables.