On a rational approximation problem in the real Hardy space H 2

Abstract

1. Introduction The problem of finding a rational approximation to a holomorphic function in a domain 52 often arises in practice. Let us give an example from system theory which has first motivated our work [l]. System theory is concerned with the study of physical systems that can be described by a relation between inputs and outputs. When considering discrete time systems, it is a convention to denote by u(z)=Cksko ukzmk, UkER,