Nonlocal symmetries and associated conservation laws for wave equations with variable speeds

We show that one can generate a class of nontrivial conservation laws for s econd-order partial differential equations using some recent results dealin g with the action of any Lie-Baklund symmetry generator of the equivalent f irst-order system on the respective conservation law. These conserved vecto rs are nonlocal as they are constructed from associated nonlocal symmetries of the partial differential equation. We demonstrate the complete procedur e on certain classes of wave equations with variable wave speeds. Some of t hese have been considered in the literature using alternative methods.