Non-Smooth Spatio-Temporal Coordinates in Nonlinear Dynamics
  This paper presents an overview of physical ideas and mathematical methods for implementing non-smooth and discontinuous substitutions in dynamical systems. General purpose of such substitutions is to bring the differential equations of motion to the form, which is convenient for further use of analytical and numerical methods of analyses. Three different types of nonsmooth transformations are discussed as follows: positional coordinate transformation, state variables transformation, and temporal transformations. Illustrating examples are provided. 
V.N. Pilipchuk
math-ph math.DS math.MP nlin.CD