Noether's Theorem for Nonsmooth Extremals of Variational Problems with   Time Delay
  We obtain a nonsmooth extension of Noether's symmetry theorem for variational problems with delayed arguments. The result is proved to be valid in the class of Lipschitz functions, as long as the delayed Euler-Lagrange extremals are restricted to those that satisfy the DuBois-Reymond necessary optimality condition. The important case of delayed variational problems with higher-order derivatives is considered as well. 
Gastao S. F. Frederico, Tatiana Odzijewicz, Delfim F. M. Torres
math.OC math-ph math.MP