Hahn-Banach operators

Ostrovskii, M.

doi:10.1090/S0002-9939-01-06037-3

Hahn-Banach operators
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by M. I. Ostrovskii PDF

Proc. Amer. Math. Soc. 129 (2001), 2923-2930 Request permission

Abstract:

We consider real spaces only. Definition. An operator $T:X\to Y$ between Banach spaces $X$ and $Y$ is called a Hahn-Banach operator if for every isometric embedding of the space $X$ into a Banach space $Z$ there exists a norm-preserving extension $\tilde T$ of $T$ to $Z$. A geometric property of Hahn-Banach operators of finite rank acting between finite-dimensional normed spaces is found. This property is used to characterize pairs of finite-dimensional normed spaces $(X,Y)$ such that there exists a Hahn-Banach operator $T:X\to Y$ of rank $k$. The latter result is a generalization of a recent result due to B. L. Chalmers and B. Shekhtman.

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