Summary of the hot GDR workshop

How do the properties of atomic nuclei change when they acquire a large amount of internal energy? How do nuclear properties vary with their temperature? The giant dipole resonance (GDR) built upon highly excited states has provided a probe for addressing this question. For example, this resonance is strongly coupled to the nuclear shape degrees of freedom. Measurements of the GDR have provided strong indications of how the nuclear deformation varies with internal energy or temperature. The most common scenario considers a nucleus with a prolate ground state deformation. When such nuclei are heated and rotated, there are signatures for a shape transition at a critical temperature Tc1(I), which is spin dependent. There is a transition from a prolate (or triaxial) shape rotating collectively at temperatures below Tc1 to an oblate shape rotating noncollectively at temperatures above Tc1. (In collective rotation, the rotation axis is perpendicular to the shape symmetry axis, whereas in noncollective rotation, the two axes coincide.)