Chaos in the low-lying collective states of even-even nuclei: Quantal fluctuations

We study the fluctuations in the spectrum and the E2 transition intensities of the low-lying collective states in heavy nuclei. Using the interacting boson model we investigate the transition from rotational nuclei to γ-unstable nuclei. Near those two limits the system exhibits regular behavior but in the transition region we observe the onset of chaos where both the level statistics and the intensities statistics are described by the Gaussian orthogonal ensemble of random matrices. The systematics of the onset of chaos within different spin/parity classes are investigated. The quantal results agree with the classical mean-field analysis.