Cross correlation of low-lying levels of even-even nuclei
  We consider the cross correlations of low-lying energy levels of nuclei belonging to small intervals of the excitation-energy ratio R_{4/2} of the first 4^+ to 2^+ states. The mean value of the cross-correlation coefficients, plotted as a function of R_{4/2} has deep minima at values of R_{4/2}=2.2 and 2.9, which correspond to the critical dynamical symmetries of the interacting Boson model. The distribution of the calculated coefficients for nuclei belonging to different R_{4/2} classes has different pattern. 
M.H. Simbel and A.Y. Abul-Magd