The giant dipole resonance as a probe of nuclear structure under extreme conditions

We investigate the properties of the Giant Dipole Resonance (GDR) built on very exotic nuclear systems: (i) High temperature, at the limit of nuclear stability. We discuss first the problem of hot nuclei formation then we ana lyse the possibility of observation of a zero- to first sound transition fo r the dipole propagation. (ii) Shape and charge equilibration in fusion dyn amics. We describe the features of direct GDR photon emissions from interme diate dinuclear systems with very exotic shapes or charge distributions for med in particular entrance channels (mass symmetry vs, charge symmetry). (i ii) Isospin. We show the effect of large charge asymmetry on propagation of isovector modes. Mixing to isoscalar components and possible new instabili ties are predicted, related to the structure of the symmetry term of effect ive interactions.