Coupling Constants in Asymptotic Expansions
  Perturbation theory is a powerful tool in manipulating dynamical system. However, it is legal only for infinitesimal perturbations. We propose to dispose this problem by means of perturbation group, and find that the coupling constant approaches to zero in the limit of high order perturbations as Dyson once expected. 
Chao-Zheng Zha (Xinjiang University, China)