Semi-classical approaches to electric giant resonances

Different fluid-dynamical approximations for Giant Resonances are reviewed. Semi classical calculations of RPA sum rules are presented. A detailed analysis of the dipole case is made, in relation with the isospin properties of the effective interaction. The dipole polarizability is investigated. The unphysical fragmentation of the RPA dipole strength is discussed, and a possible explanation is given, which relates this erroneous feature to too low values of the surface symmetry coefficient