A solution to the Riquier-Neymann problem for polyharmonic equations in a ball

In this paper, an elementary solution for polyharmonic equations is determined and its properties are given. This elementary solution coincides with previously known elementary solutions of biharmonic and triharmonic equations. Using the elementary solution, an integral representation of the solutions of a non-homogeneous polyharmonic equation in a bounded domain with a smooth boundary is found. Based on the integral representation, the solvability of the Riquier-Neumann problem is investigated. First, the concept of the Green's function of the Riquier-Neumann problem is defined, and then the Green's function is proved. Using the integral representation of the solutions of the polyharmonic equation and the Green's function of the Riquier-Neumann problem, the integral representation of the solution of the Riquier-Neumann problem in a unit ball is found. An example of the solution of the Neumann problem for the Poisson equation with the simplest right-hand side is given, which is necessary in what follows.
On the basis of the Green's function of the Riquier-Neumann problem, a theorem on the integral representation of the solution of the Riquier-Neumann boundary value problem with boundary data, the integral of which over the unit sphere vanishes, is proved. In conclusion, on the basis of the theorem, an example of calculating the solution of the Riquier-Neumann problem with boundary functions coinciding with the traces of homogeneous harmonic polynomials on a unit sphere is given.