While bulk properties of stable nuclei are successfully reproduced by mean-field theories employing effective interactions, the dependence of the centroid energy of the electric giant dipole resonance on the nucleon number A is not. This problem is cured by considering many-particle correlations beyond mean-field theory, which we do within the "Quasiparticle Time Blocking Approximation". The electric giant dipole resonances in $^{ 16}$O, $^{ 40}$Ca, and $^{ 208}$Pb are calculated using two new Skyrme interactions.
Categories: nucl-th