Living at the edge of stability: The role of continuum and three-nucleon forces

Nuclear structure at and reactions at the dripline is a challenging undertaking. In order to give reliable predictions for future experiments and describing the exotic phenomena that occurs as we move beyond the valley of stability we need a theory that properly accounts for; (i) the effects of three nucleon forces, (ii) the presence of open decay channels and particle continuum, and (iii) many-nucleon correlations. We aim to fill this gap by using interactions from chiral effective field theory together with a schematic potential that accounts for the effects of three-nucleon forces, a Berggren basis that treats bound and continuum states on equal footing, and coupled-cluster theory to properly account for many-nucleon correlations. We apply this approach to the computation of binding energies, radii and excited states in the neutron rich oxygen [1] and calcium isotopes [2]. We show that effects of three-nucleon forces are essential in placing the dripline at $^{24}$O and for explaining the shell closure in $^{48}$Ca. We find a weak shell closure in $^{54}$Ca, assign spin and parities to several unknown levels in oxygen and calcium isotopes, and in particular we find due to continuum coupling the level ordering of the states in the \textit{gds} shell are reversed compared to the na\"ive shell model picture as we move towards $^{60}$Ca. We also note that a saturation of total binding sets in around $^{60}$Ca, indicating that the $^{60}$Ca is either a very weakly bound or unbound nucleus. By computing overlap functions we have also extended our approach to compute reaction observables, and we present results for low-energy elastic proton scattering on calcium isotopes. The results are promising and open up new possibilities to perform predictive and microscopic structure and reaction calculations towards the dripline. \\[4pt] [1] G. Hagen, M. Hjorth-Jensen, G. R. Jansen, R. Machleidt, and T. Papenbrock, Phys. Rev. Lett. (2012), arXiv:1204.3612v1 \\[0pt] [2] G. Hagen, M. Hjorth-Jensen, G. R. Jansen, R. Machleidt, and T. Papenbrock, arXiv:1202.2839v1 (2012)