Uniform semiclassical approach to fidelity decay in the deep Lyapunov   regime
  We use the uniform semiclassical approximation in order to derive the fidelity decay in the regime of large perturbations.   Numerical computations are presented which agree with our theoretical predictions.   Moreover, our theory allows to explain previous findings, such as the deviation from the Lyapunov decay rate in cases where the classical finite-time instability is non-uniform in phase space. 
Wen-ge Wang, G. Casati, Baowen Li, and T. Prosen