EMMI workshop: Neutron Matter in Astrophysics: From Neutron Stars to the r-Process

This talk will discuss the impact of chiral three-nucleon forces on neutron-rich nuclei and on neutron-rich matter. I will show that three-nucleon forces lead to repulsive contributions to the interactions among valence neutrons that change the location of the neutron drip line from 28O to the experimentally observed 24O. This three-nucleon mechanism provides the first microscopic explanation of the oxygen anomaly in the neutron drip line and can impact the prediction of the most neutron-rich nuclei and the synthesis of heavy elements in neutron-rich environments. In addition, our microscopic calculations based on the same interactions constrain the properties of dense matter below nuclear densities to a much higher degree than is reflected in current neutron star modeling. Combined with observed neutron star masses, our results lead to a radius R = 11.8 +/- 2.1 km for a M = 1.4 M_sun neutron star, where the theoretical error is due, in about equal amounts, to uncertainties in many-body forces and to the extrapolation to high densities.