Linear structures of norm-attaining Lipschitz functions and their complements

Fuente: arXiv
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Main Authors: Choi, Geunsu, Jung, Mingu, Lee, Han Ju, Roldan, Oscar
Format: Preprint
Published: 2024
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author Choi, Geunsu
Jung, Mingu
Lee, Han Ju
Roldan, Oscar
author_facet Choi, Geunsu
Jung, Mingu
Lee, Han Ju
Roldan, Oscar
contents We solve two main questions on linear structures of (non-)norm-attaining Lipschitz functions. First, we show that for every infinite metric space $M$, the set consisting of Lipschitz functions on $M$ which do not strongly attain their norm and the zero contains an isometric copy of $\ell_\infty$, and moreover, those functions can be chosen not to attain their norm as functionals on the Lipschitz-free space over $M$. Second, we prove that for every infinite metric space $M$, neither the set of strongly norm-attaining Lipschitz functions on $M$ nor the union of its complement with zero is ever a linear space. Furthermore, we observe that the set consisting of Lipschitz functions which cannot be approximated by strongly norm-attaining ones and the zero element contains $\ell_\infty$ isometrically in all the known cases. Some natural observations and spaceability results are also investigated for Lipschitz functions that attain their norm in one way but do not in another, for several norm-attainment notions considered in the literature.
format Preprint
id arxiv_https___arxiv_org_abs_2404_07599
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Linear structures of norm-attaining Lipschitz functions and their complements
Choi, Geunsu
Jung, Mingu
Lee, Han Ju
Roldan, Oscar
Functional Analysis
We solve two main questions on linear structures of (non-)norm-attaining Lipschitz functions. First, we show that for every infinite metric space $M$, the set consisting of Lipschitz functions on $M$ which do not strongly attain their norm and the zero contains an isometric copy of $\ell_\infty$, and moreover, those functions can be chosen not to attain their norm as functionals on the Lipschitz-free space over $M$. Second, we prove that for every infinite metric space $M$, neither the set of strongly norm-attaining Lipschitz functions on $M$ nor the union of its complement with zero is ever a linear space. Furthermore, we observe that the set consisting of Lipschitz functions which cannot be approximated by strongly norm-attaining ones and the zero element contains $\ell_\infty$ isometrically in all the known cases. Some natural observations and spaceability results are also investigated for Lipschitz functions that attain their norm in one way but do not in another, for several norm-attainment notions considered in the literature.
title Linear structures of norm-attaining Lipschitz functions and their complements
topic Functional Analysis
url https://arxiv.org/abs/2404.07599