Coexistence of Ordered and Chaotic States in Nuclear Structure

In atomic nuclei, as in other many–body systems, the classical phase space is mixed, so ordered and chaotic states generally coexist [1]. In this contribution we discuss some models, showing the transition from order to chaos. In several cases a clear correspondence between classical and quantum chaos has been established. In particular the transition from ordered to chaotic states will be discussed in the framework of the shell and roto–vibrational models. The spectral statistics of low–lying states of several fp shell nuclei are studied with realistic shell–model calculations [2]. Furthermore, for the roto–vibrational model the Gaussian curvature criterion of the potential energy clearly shows the transition from order to chaos for different values of rotational frequency [3].