Periodic Schrödinger Operators with (Non-Periodic) Magnetic and Electric Potentials.
We describe a method of calculation of all physical algebraic-geometrical solutions of KP-equations.
In this paper we prove existence of periodic solutions to a nonlinear evolution system of second order partial differential equations involving the pseudo-Laplacian operator. To show the existence of periodic solutions we use Faedo-Galerkin method with a Schauder fixed point argument.