Approximation by rational functions on doubly connected domains in weighted generalized grand Smirnov classes

UDC 517.5 Let be a doubly connected domain bounded by two rectifiable Carleson curves. In this work, we use the higher modulus of smoothness in order to investigate the approximation properties of -Faber–Laurent rational functions in the subclass of weighted generalized grand Smirnov classes of analytic functions.

On Riemann problem in weighted Smirnov classes with general weight

Weighted Smirnov classes in bounded and unbounded domains are defined in this work. Nonhomogeneous Riemann problems with a measurable coefficient whose argument is a piecewise continuous function are considered in these classes. A Muckenhoupt type condition is imposed on the weight function and the orthogonality condition is found for the solvability of nonhomogeneous problem in weighted Smirnov classes, and the formula for the index of the problem is derived. Some special cases with power type weight function are also considered,and conditions on degeneration order are found.