Isospin splitting of the giant dipole resonance in the s-d shell and the interacting boson model

A phenomenological algebraic approach to nuclear isovector excitations is discussed within the framework of the interacting boson model. Analytic formulae are obtained for isospin splittings and excitation strengths of the giant dipole resonance in deformed nuclei. An application of the formalism to ${}_{}{}^{26}{}_{}{}^{}\mathrm{Mg}$ is presented, where both schematic and realistic calculations have been performed.