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On meromorphic approximation
Authors:VA Prokhorov  EB Saff
Institution:(1) Department of Mathematics and Statistics, University of South Alabama, Mobile, AL 36688-0002, USA;(2) Institute for Constructive Mathematics, Department of Mathematics, University of South Florida, Tampa, FL 33620-5700, USA
Abstract:Let G be a bounded N-connected domain, the boundary Gamma of which consists of closed analytic Jordan curves. We assume that 0epsiG. For any nonnegative integers n and m, denote by phmmat n,m the class of all meromorphic functions on G that can be represented in the form h=p/qz m , where p belongs to the Smirnov class E infin(G), q is a polynomial of degree at most n, qnequiv0. Theorems giving necessary and sufficient conditions for a function belonging to the class phmmat n,m to be an element of best approximation to a continuous function f on Gamma in the space L infin(Gamma) by functions in the class phmmat n,m are proved. Some questions concerning orthogonal polynomials and the theory of Hankel operators are also considered.
Keywords:meromorphic approximation  best approximation  Hankel operator  singular numbers  orthogonal polynomials
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