On Hahn-Banach smoothness and related properties in Banach spaces

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1. Verfasser: Daptari, Soumitra
Format: Preprint
Veröffentlicht: 2024
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author Daptari, Soumitra
author_facet Daptari, Soumitra
contents In this paper, we study several variants of Hahn-Banach smoothness, viz., property-$(SU)$/$(HB)$/$(wU)$, where property-$(SU)$ and property-$(HB)$ are stronger notions and property-$(wU)$ is a weaker notion of Hahn-Banach smoothness. We characterize property-$(wU)$ and property-$(HB)$. It is observed that $L_1(μ)$ has property-$(wU)$ in $L_1(μ,(\mathbb{R}^2,\|.\|_2))$ but it does not have property-$(U)$ in $L_1(μ,(\mathbb{R}^2,\|.\|_2))$ for a non-atomic measure $μ$. We derive a sufficient condition when property-$(wU)$ is equivalent to property-$(U)$ of a subspace. It is observed that these properties are separably determined. Finally, finite-dimensional and finite co-dimensional subspaces of $c_0$, $\ell_p$ ($1\leq p<\infty$) having these properties are characterized.
format Preprint
id arxiv_https___arxiv_org_abs_2403_03453
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle On Hahn-Banach smoothness and related properties in Banach spaces
Daptari, Soumitra
Functional Analysis
46A22, 46B10, 46B25, 46B20, 46B45
In this paper, we study several variants of Hahn-Banach smoothness, viz., property-$(SU)$/$(HB)$/$(wU)$, where property-$(SU)$ and property-$(HB)$ are stronger notions and property-$(wU)$ is a weaker notion of Hahn-Banach smoothness. We characterize property-$(wU)$ and property-$(HB)$. It is observed that $L_1(μ)$ has property-$(wU)$ in $L_1(μ,(\mathbb{R}^2,\|.\|_2))$ but it does not have property-$(U)$ in $L_1(μ,(\mathbb{R}^2,\|.\|_2))$ for a non-atomic measure $μ$. We derive a sufficient condition when property-$(wU)$ is equivalent to property-$(U)$ of a subspace. It is observed that these properties are separably determined. Finally, finite-dimensional and finite co-dimensional subspaces of $c_0$, $\ell_p$ ($1\leq p<\infty$) having these properties are characterized.
title On Hahn-Banach smoothness and related properties in Banach spaces
topic Functional Analysis
46A22, 46B10, 46B25, 46B20, 46B45
url https://arxiv.org/abs/2403.03453