Multi-dimensional conservation laws and integrable systems

In this paper, we introduce a new property of two-dimensional integrable hydrodynamic chains—existence of infinitely many local three-dimensional conservation laws for pairs of integrable two-dimensional commuting flows. Infinitely many local three-dimensional conservation laws for the Benney commuting hydrodynamic chains are constructed. As a by-product, we established a new method for computation of local conservation laws for three-dimensional integrable systems. The Mikhalëv equation and the dispersionless limit of the Kadomtsev-Petviashvili equation are investigated. All known local and infinitely many new quasilocal three-dimensional conservation laws are presented. Also four-dimensional conservation laws are considered for couples of three-dimensional integrable quasilinear systems and for triplets of corresponding hydrodynamic chains.