Ab Initio Shell Model Calculations with Three-Body Effective Interactions for $\mathit{p}$-Shell Nuclei

We present a qualitative improvement of the ab initio no-core shell model (NCSM) approach by implementing three-body interaction capability for $p$-shell nuclei. We report the first calculations using three-body effective interactions derived from realistic nucleon-nucleon potentials for ${}^6\mathrm{Li}$, ${}^8\mathrm{Be}$, and ${}^{10}\mathrm{B}$ and demonstrate that the use of three-body effective interactions speeds up the convergence of the NCSM approach. For ${}^{10}\mathrm{B}$, we predict $J^{\pi }{T=1\mathrm{}}^{+}0$ ground state, contrary to the experimental observation of $3^{+}0$, when the $\mathrm{AV}{8}^{\prime }$ potential is used, indicating the need for true three-body forces.