On the uniqueness of extension and unique best approximation in the dual of an asymmetric normed linear space

Costică Mustăţa

doi:10.33993/jnaat322-747

Authors

Costică Mustăţa Tiberiu Popoviciu, Institute of Numerical Analysis, Romanian Academy, Romania

DOI:

https://doi.org/10.33993/jnaat322-747

Keywords:

asymmetric normed spaces, extensions preserving asymmetric norm, best approximation

Abstract views: 285

Abstract

A well known result of R. R. Phelps (1960) asserts that in order that every linear continuous functional, defined on a subspace \(Y\) of a real normed space \(X\), have a unique norm preserving extension it is necessary and sufficient that its annihilator \(Y^\bot\) be a Chebyshevian subspace of \(X^\ast\). The aim of this note is to show that this result holds also in the case of spaces with asymmetric norm.

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References

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