  We investigate the influence of phenomenological three-nucleon interactions
on the systematics of ground-state energies and charge radii throughout the
whole nuclear mass range from 4-He to 208-Pb. The three-nucleon interactions
supplement unitarily transformed two-body interactions constructed within the
Unitary Correlation Operator Method or the Similarity Renormalization Group
approach. To be able to address heavy nuclei as well, we treat the many-body
problem in Hartree-Fock plus many-body perturbation theory, which is sufficient
to assess the systematics of energies and radii, and limit ourselves to
regularized three-body contact interactions. We show that even with such a
simplistic three-nucleon interaction a simultaneous reproduction of the
experimental ground-state energies and charge radii can be achieved, which is
not possible with unitarily transformed two-body interactions alone.
