At the heart of modern theoretical descriptions of medium-mass nuclei are three-nucleon (3N) forces, whose impact on systems far from stability represents a current frontier in nuclear structure theory. I will discuss our microscopic framework, based on chiral effective field theory (χEFT) and renormalization group methods, in which exotic nuclei are explored systematically from NN and 3N forces. In this approach it was found that 3N forces are essential to explain why 24O is the heaviest oxygen isotope and to predict the evolution of shell structure in neutron-rich calcium isotopes without empirical adjustments.
This talk will focus on a number of recent studies pointing to future directions of this work. I will first discuss the evolution of shell structure in calcium from the viewpoint of pairing gaps and two-neutron separation energies, emphasizing the distinct role of many-body processes and 3N forces in a microscopic description of nuclear pairing. I then extend this approach to investigate exotic proton-rich nuclei, where 3N forces are vital to describe both ground- and excited-state properties of N = 8 and N = 20 isotones to the proton dripline. Finally I will present developments towards a non-empirical calculation of the neutrinoless ββ decay nuclear matrix element in 48Ca, 76Ge, and 82Se, based on χEFT, a key ingredient in determining the absolute mass scale of neutrinos. Finally, I will highlight collaborative efforts with radioactive beam experiments that are a key component of this work.
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