Dirichlet and Neumann Boundary Value Problems for the Polyharmonic Equation in the Unit Ball

In the previous author’s works, a representation of the solution of the Dirichlet boundary value problem for the biharmonic equation in terms of Green’s function is found, and then it is shown that this representation for a ball can be written in the form of the well-known Almansi formula with explicitly defined harmonic components. In this paper, this idea is extended to the Dirichlet boundary value problem for the polyharmonic equation, but without invoking the Green’s function. It turned out to find an explicit representation of the harmonic components of the m-harmonic function, which is a solution to the Dirichlet boundary value problem, in terms of m solutions to the Dirichlet boundary value problems for the Laplace equation in the unit ball. Then, using this representation, an explicit formula for the harmonic components of the solution to the Neumann boundary value problem for the polyharmonic equation in the unit ball is obtained. Examples are given that illustrate all stages of constructing solutions to the problems under consideration.

Polyharmonic Decomposition of a Digital Image

A decomposition of the space L2(Q) into a direct sum of polyharmonic subspaces is obtained. The completeness of shift systems of the fundamental solution of the polyharmonic equation is proved. A convergent algorithm for solving the problem of separating the polyharmonic component of a function from L2(Q) is developed. The resulting decomposition is applied to some digital image processing problems; the results of computational experiments are presented.