Differential analysis of nonlinear systems: revisiting the pendulum   example
  Differential analysis aims at inferring global properties of nonlinear behaviors from the local analysis of the linearized dynamics. The paper motivates and illustrates the use of differential analysis on the nonlinear pendulum model, an archetype example of nonlinear behavior. Special emphasis is put on recent work by the authors in this area, which includes a differential Lyapunov framework for contraction analysis and the concept of differential positivity. 
Fulvio Forni, Rodolphe Sepulchre
cs.SY math.DS