Tunable-fidelity wave functions for ab initio scattering and reactions

The no-core shell model (NCSM) is a first-principle method that computes static properties of light nuclei employing an expansion of the many-body wave function onto a basis of Slater determinants. Extensions of the NCSM (such as the NCSM with continuum or NCSMC) have further allowed for the description of light-ion reactions relevant to astrophysics and nuclear technology applications. Nevertheless, the reach of the NCSMC is hindered by an explosion in the problem dimensionality as nuclei beyond oxygen are targeted. From the large number of basis states that are needed to compute nuclear properties in the NCSM, however, only a smaller subset is relevant in the description of reactions. In this talk, we discuss an approach that aims to circumvent the dimensionality explosion problem within the NCSM (and NCSMC) by allowing for wave functions of near-continuous fidelity to be generated. We present first findings on the convergence properties of the approach as well as demonstrate its efficacy when describing heavier nuclei.