Group equivariant Radon-Nikodým property and its characterizations

Fuente: arXiv
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Main Authors: Dantas, Sheldon, Doucha, Michal, Jung, Mingu, Raunig, Tomáš
Format: Preprint
Published: 2025
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author Dantas, Sheldon
Doucha, Michal
Jung, Mingu
Raunig, Tomáš
author_facet Dantas, Sheldon
Doucha, Michal
Jung, Mingu
Raunig, Tomáš
contents We introduce and study equivariant versions of the Radon-Nikodým property for Banach spaces, together with the closely related notions such as dentability, the Bishop-Phelps and Krein-Milman properties, and Lindenstrauss' property A, all considered in the presence of a continuous group action by linear isometries. While in the classical setting the Radon-Nikodým property, the Bishop-Phelps property and dentability are equivalent, the equivariant situation turns out to depend essentially on the acting group and requires nontrivial tools from abstract harmonic analysis and representation theory. We establish several implications among the equivariant counterparts of these properties. Namely, for a compact group $G$, the $G$-Bishop-Phelps property implies strong $G$-dentability, which in turn implies the $G$-Krein-Milman property. Moreover, for a locally compact, $σ$-compact, separable group $G$, weak $G$-dentability is equivalent to the $G$-Radon-Nikodým property.
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institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Group equivariant Radon-Nikodým property and its characterizations
Dantas, Sheldon
Doucha, Michal
Jung, Mingu
Raunig, Tomáš
Functional Analysis
We introduce and study equivariant versions of the Radon-Nikodým property for Banach spaces, together with the closely related notions such as dentability, the Bishop-Phelps and Krein-Milman properties, and Lindenstrauss' property A, all considered in the presence of a continuous group action by linear isometries. While in the classical setting the Radon-Nikodým property, the Bishop-Phelps property and dentability are equivalent, the equivariant situation turns out to depend essentially on the acting group and requires nontrivial tools from abstract harmonic analysis and representation theory. We establish several implications among the equivariant counterparts of these properties. Namely, for a compact group $G$, the $G$-Bishop-Phelps property implies strong $G$-dentability, which in turn implies the $G$-Krein-Milman property. Moreover, for a locally compact, $σ$-compact, separable group $G$, weak $G$-dentability is equivalent to the $G$-Radon-Nikodým property.
title Group equivariant Radon-Nikodým property and its characterizations
topic Functional Analysis
url https://arxiv.org/abs/2510.23100