MODELING COMPLEX NUCLEAR-SPECTRA - REGULARITY VERSUS CHAOS

A statistical analysis of the spectrum of two-particle-two-hole doorwa y states in a finite nucleus is performed. On the unperturbed mean-fie ld level sizable attractive correlations are present in such a spectru m. Including particle-hole rescattering effects via the residual inter action introduces repulsive dynamical correlations which generate the fluctuation properties characteristic of the Gaussian orthogonal ensem ble. This signals that the underlying dynamics becomes chaotic. This f eature turns out to be independent of the detailed form of the residua l interaction and hence reflects the generic nature of the fluctuation s studied.