Differential Contour-Solid problem of Analytic Functions

Abstract

The paper gives a survey of results completely solving the differential contour-solid problem of analytic functions in an open subset G of the complex plane, which was discussed as an open problem at the informal seminar held in 1994 in Zurich by participants of the International Congress of Mathematicians. This problem has a long prehistory and includes questions (unsolved at that time) concerning conditions of validity of differential contour-solid statements on the continuous extendability of a derivative to boundary points and on the differentiability of an analytic function at boundary points of the set G. In June, 1995, the author established that these statements are always true for arbitrary open sets G and any boundary points. These and more general theorems are given in this paper. We also present some other results, among which contour-solid theorems and a representation formula for the generalized solution of the Dirichlet problem for the derivative of a function should be mentioned.