No abstract

Because of the time reversal invariance of the angular momentum operator J2, the average energies and variances at fixed J for random two-body Hamiltonians exhibit odd-even- J staggering that may be especially strong for J = 0. It is shown that upon ensemble averaging over random runs, this behavior is reflected in the yrast states. Displaced (attractive) random ensembles lead to rotational spectra with strongly enhanced B(E2) transitions for a certain class of model spaces. It is explained how to generalize these results to other forms of collectivity.

Accepted for publication in Physical Review CWe discuss the Garvey-Kelson mass relations in an extended formalism and show how they can be used to test and improve the consistency of the most commonly used mass formulae, in order to achieve more accurate predictions