Nuclear structure studies within the realistic shell model

The role of three-nucleon forces on structure properties of nuclei is discussed within the realistic shell model. Calculations are performed by employing effective shell-model Hamiltonians derived by way of many-perturbation theory from chiral potentials including the nucleon-nucleon and three-nucleon components. A sketch of the formalism in treating the three-nucleon force is given and some selected results for f p- and pshell nuclei are shown. Particular attention is devoted to the effects of the three-nucleon force on the monopole component of the effective shell-model interaction by showing how relevant they are in correcting the monopole interaction derived from the nucleon-nucleon force only and correctly describing the formation of shell structure as well as the enhancement in the spin-orbit splitting. A decomposition scheme based on the rank of irreducible tensors forming the three-nucleon force at the next-to-next-to-leading order is also presented to recognize their impact on the spin-orbit enhancement.