Anomalous slow fidelity decay for symmetry breaking perturbations
  Symmetries as well as other special conditions can cause anomalous slowing down of fidelity decay. These situations will be characterized, and a family of random matrix models to emulate them generically presented. An analytic solution based on exponentiated linear response will be given. For one representative case the exact solution is obtained from a supersymmetric calculation. The results agree well with dynamical calculations for a kicked top. 
T. Gorin, H. Kohler, T. Prosen, T. H. Seligman, H.-J. Stoeckmann and   M. Znidaric