The Delta I=4 Bifurcation in Superdeformed Bands
  The origin of the Delta I=4 staggering effect which has recently been observed in several superdeformed bands is discussed. The Hamamoto and Mottelson model, which is based on a phenomenological parametrization of the hamiltonian as a quartic function of angular momentum, is analyzed. A stability of the description with respect to the C_4 - symmetry breaking terms is studied. 
P. Magierski, K. Burzynski, J. Dobaczewski, and W. Nazarewicz