Recent results on energy-level fluctuations

Abstract

We comment on the present theoretical status of the distant-neighbor spacing distributions in view of recent experimental results. In particular, we stress that both the Gaussian orthogonal and the two-body random Hamiltonian ensembles predict essentially identical spacing distributions for the highly excited part of the spectrum; this is true also for the other available measures. Thus the statistical analysis of spectrum fluctuations does not inform us about the two-body or multibody nature of the interaction. We point out also that, when due attention is paid to the variation of level density with excitation, the fluctuation pattern observed in the slow-neutron domain is found to extend throughout the entire spectrum.