Dependence of alpha in Peak Norms and Best Peak Norms Approximation

Author: Yang C.

Source: Journal of Approximation Theory, Volume 104, Number 1, May 2000 , pp. 164-182(19)

Publisher: Academic Press

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Abstract:

Let C[0, 1] be the space of all continuous functions defined on [0, 1] and U be an n dimensional subspace of C[0, 1]. A peak norm, or alpha-norm for 0<alphales1, alpha-norm is defined by VerbarfVerbaralpha=1alpha sup{intA |f| dmu mid mu(A)=alphaAsub[0, 1]}, where mu denotes the Lebesgue measure. We say pisinU is a best alpha-norm approximant to f from U if Dalpha(f)=Verbarf-pVerbaralpha=inf{Verbarf-uVerbaralpha mid uisinU}. In this paper we shall study VerbarfVerbaralpha, Dalpha(f) and Palpha(f)={pisinU mid Verbarf-pVerbaralpha=Dalpha(f)} as functions of alpha for fixed f. We shall show their continuous dependence on alpha and differentiability with respect to alpha. Copyright 2000 Academic Press.

Keywords: best approximation; peak norm; alpha-norm; continuity; differentiability

Language: English

Document Type: Research article

Affiliations: Department of Mathematics, West Virginia University, Institute of Technology, Montgomery, West Virginia, 25136

Publication date: 2000-05-01

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