C12properties with evolved chiral three-nucleon interactions

Abstract

We investigate selected static and transition properties of $^{12}\mathrm{C}$ using ab initio no-core shell model (NCSM) methods with chiral two- and three-nucleon interactions. We adopt the similarity renormalization group (SRG) to assist convergence including up to three-nucleon ($3N$) contributions. We examine the dependencies of the ${}^{12}$C observables on the SRG evolution scale and on the model-space parameters. We obtain nearly converged low-lying excitation spectra. We compare results of the full NCSM with the importance truncated NCSM in large model spaces for benchmarking purposes. We highlight the effects of the chiral $3N$ interaction on several spectroscopic observables. The agreement of some observables with experiment is improved significantly by the inclusion of $3N$ interactions, e.g., the $B(M1)$ from the first ${J}^{\ensuremath{\pi}}T={1}^{+}1$ state to the ground state. However, in some cases the agreement deteriorates, e.g., for the excitation energy of the first ${1}^{+}0$ state, leaving room for improved next-generation chiral Hamiltonians.