Bridging scales in nuclear physics
In this thesis we present the ab initio no-core shell model (NCSM) and use this framework to study light atomic nuclei with realistic nucleon-nucleon interactions. In particular, we present results for radii and ground-state energies of systems with up to twelve nucleons. Since the NCSM uses a finite harmonic oscillator basis, we need to apply corrections to compute basis-independent results. The derivation, application, and analysis of such corrections constitute important results that are presented in this thesis. Furthermore, we compute three-body overlap functions from microscopic wave functions obtained in the NCSM in order to study the onset of clusterization in many-body systems. In particular, we study the Borromean two-neutron halo state in 6He by computing the overlap function < 6He(0+)|4He(0+) + n + n >. We can thereby demonstrate that the clusterization is driven by the Pauli principle. Finally, we develop state-of-the-art computational tools to efficiently extract one- and two-body transition densities from microscopic wave functions. These quantities are important properties of many-body systems and are keys to compute structural observables. In this work we study the core-swelling effect in 6He by computing the average distance between nucleons.