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Article #195

A question about Nevallina-Pick theory

#195
From: Onur Toker
Date: Wed, 27 Jan 1993 01:43
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	Let m(z) be an inner function defined on the unit disc D, and
let z_1,...,z_n be finitely many points on D. It is known that there
exists a rational inner function m_f(z) which interpolates m(z) at
z_1,..,z_n (This is a classical result in Nevallina-Pick interpolation
theory).
	My question is about the parametrization of all such m_f's? 
Does anybody know anything about 

	(1) parametrization of all such m_f's? 

	(2) given N, is there an m_f of order N?

Remarks: The parametrization of all analytic functions with norm <= 1
and satisfying the above interpolation conditions is known.
Furthermore if we know the definition of the function m(z) and the
numerical values of points z_1,...,z_n then question (2) can be
answered by reducing it to a linear algebra problem and checking
whether  a system of equations has a solution or not. But I don't know
whether (2) holds for all sufficently large N values (or for N > 2*n).

	O.Toker
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From: tokero@bode.eng.ohio-state.edu (Onur Toker)
Newsgroups: sci.math.research
Subject: A question about Nevallina-Pick theory
Message-ID: <1993Jan27.014313.19660@ee.eng.ohio-state.edu>
Date: 27 Jan 93 01:43:13 GMT
Article-I.D.: ee.1993Jan27.014313.19660
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