SYMMETRY AND CONSERVATION-LAWS OF DIFFERENTIAL-EQUATIONS

A method is presented for associating a constant of the motion with th e (pseudo)symmetries of certain differential equations. The method req uires the existence of an invariant differential form but does not req uire, as does Noether's theorem, that the differential equations follo w from a variational principle. The method does not require any integr ations. Applications to divergence-free equations and to Hamiltonian s ystems are discussed.