Collectivity in neutron-rich neon isotopes from ab-initio methods

We compute the low-lying collective structure of ^20-34Ne using ab-initio coupled-cluster methods and chiral nucleon-nucleon and three-nucleon interactions. For ^20-30Ne we accurately describe the first 2⁺ and 4⁺ energies and the quadrupole transitions from the first 2⁺ to the ground-state. For ^32,34Ne less is known and we predict that they are strongly deformed and collective. To understand how individual terms of the nuclear Hamiltonian impacts deformation we use emulators of the E(4+)/E(2+) ratio and perform a global sensitivity analysis in ^20,32Ne and ³⁴Mg. We find that more than 50% of deformation is driven by S-wave contacts and that adding short-range repulsion (reducing pairing) increases deformation. These are first steps towards answering the question: What drives deformation in nuclei?