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arXiv · 2002.04308

Star-finite coverings of Banach spaces

Carlo Alberto De Bernardi·Jacopo Somaglia·Libor Vesely
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Abstract

We study star-finite coverings of infinite-dimensional normed spaces. A family of sets is called star-finite if each of its members intersects only finitely many other members of the family. It follows by our results that an LUR or a uniformly Fr\'echet smooth infinite-dimensional Banach space does not admit star-finite coverings by closed balls. On the other hand, we present a quite involved construction proving existence of a star-finite covering of $c_0(\Gamma)$ by Fr\'echet smooth centrally symmetric bounded convex bodies. A similar but simpler construction shows that every normed space of countable dimension (and hence incomplete) has a star-finite covering by closed balls.

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Carlo Alberto De Bernardi, Jacopo Somaglia, Libor Vesely. 2020-02-11. Star-finite coverings of Banach spaces. https://arxiv.org/abs/2002.04308

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