Constants and pseudo-constants of the Kadomtsev-Petviashvili equation

Elucidating earlier work, it is shown that the Kadomtsev-Petviashvili equation has n+ 2 constants for all n≥ 0. It also has a pseudo-constant from which the constants can be obtained by differentiation with respect to time. The pseudo-constant can be obtained from a basis functional Jn(n+2)= -1/18 [unk] yn+2qby taking repeated Poisson brackets with the Hamiltonian.