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A $\Delta$-point $x$ of a Banach space is a norm one element that is arbitrarily close to convex combinations of elements in the unit ball that are almost at distance $2$ from $x$. If, in addition, every point in the unit ball is…

Functional Analysis · Mathematics 2018-12-07 Trond Arnold Abrahamsen , Rainis Haller , Vegard Lima , Katriin Pirk

If $X$ is an infinite-dimensional uniform algebra, if $X$ has the Daugavet property or if $X$ is a proper $M$-embedded space, every relatively weakly open subset of the unit ball of the Banach space $X$ is known to have diameter 2, i.e.,…

Functional Analysis · Mathematics 2013-04-29 Trond Abrahamsen , Vegard Lima , Olav Nygaard

We introduce relative versions of Daugavet-points and the Daugavet property, where the Daugavet-behavior is localized inside of some supporting slice. These points present striking similarities with Daugavet-points, but lie strictly between…

We study the existence of Daugavet- and delta-points in the unit sphere of Banach spaces with a $1$-unconditional basis. A norm one element $x$ in a Banach space is a Daugavet-point (resp. delta-point) if every element in the unit ball…

Functional Analysis · Mathematics 2020-07-10 Trond A. Abrahamsen , Vegard Lima , André Martiny , Stanimir Troyanski

We show that all the symmetric projective tensor products of a Banach space $X$ have the Daugavet property provided $X$ has the Daugavet property and either $X$ is an $L_1$-predual (i.e.\ $X^*$ is isometric to an $L_1$-space) or $X$ is a…

Functional Analysis · Mathematics 2020-11-02 Miguel Martin , Abraham Rueda Zoca

A Daugavet-point (resp.~$\Delta$-point) of a Banach space is a norm one element $x$ for which every point in the unit ball (resp.~element $x$ itself) is in the closed convex hull of unit ball elements that are almost at distance 2 from $x$.…

Functional Analysis · Mathematics 2020-01-20 Rainis Haller , Katriin Pirk , Triinu Veeorg

The aim of this note is to provide several variants of the diameter two properties for Banach spaces. We study such properties looking for the abundance of diametral points, which holds in the setting of Banach spaces with the Daugavet…

Functional Analysis · Mathematics 2016-04-18 Julio Becerra Guerrero , Ginés López Pérez , Abraham Rueda Zoca

We introduce two new notions called the Daugavet constant and $\Delta$-constant of a point, which measure quantitatively how far the point is from being Daugavet point and $\Delta$-point and allow us to study Daugavet and $\Delta$-points in…

Functional Analysis · Mathematics 2024-12-18 Geunsu Choi , Mingu Jung

We introduce a vector-valued version of a uniform algebra, called the vector-valued function space over a uniform algebra. The diameter two properties of the vector-valued function space over a uniform algebra on an infinite compact…

Functional Analysis · Mathematics 2021-03-17 Han Ju Lee , Hyung-Joon Tag

In this article, we study the diameter two properties (D2Ps), the diametral diameter two properties (diametral D2Ps), and the Daugavet property in Orlicz-Lorentz spaces equipped with the Luxemburg norm. First, we characterize the…

Functional Analysis · Mathematics 2023-04-06 Anna Kamińska , Han Ju Lee , Hyung-Joon Tag

We study Daugavet- and $\Delta$-points in Banach spaces. A norm one element $x$ is a Daugavet-point (respectively a $\Delta$-point) if in every slice of the unit ball (respectively in every slice of the unit ball containing $x$) you can…

Functional Analysis · Mathematics 2022-03-29 Trond A. Abrahamsen , Vegard Lima , André Martiny , Yoël Perreau

We show that the duals of Banach algebras of scalar-valued bounded holomorphic functions on the open unit ball $B_E$ of a Banach space $E$ lack weak$^*$-strongly exposed points. Consequently, we obtain that some Banach algebras of…

Functional Analysis · Mathematics 2023-03-27 Mingu Jung

We introduce the super alternative Daugavet property (super ADP) which lies strictly between the Daugavet property and the Alternative Daugavet property as follows. A Banach space $X$ has the super ADP if for every element $x$ in the unit…

Functional Analysis · Mathematics 2026-04-15 Johann Langemets , Marcus Lõo , Miguel Martín , Yoël Perreau , Abraham Rueda Zoca

We introduce extensions of $\Delta$-points and Daugavet points in which slices are replaced by relative weakly open subsets (super $\Delta$-points and super Daugavet points) or by convex combinations of slices (ccs $\Delta$-points and ccs…

Functional Analysis · Mathematics 2023-01-12 Miguel Martin , Yoël Perreau , Abraham Rueda Zoca

We give a characterisation of the separable Banach spaces with the Daugavet property which is applied to study the Daugavet property in the projective tensor product of an $L$-embedded space with another non-zero Banach space. The former…

Functional Analysis · Mathematics 2018-02-21 Abraham Rueda Zoca

In this note, we prove that the Daugavet property implies the polynomial Daugavet property, solving a longstanding open problem in the field. Our approach is based on showing that a geometric characterization of the Daugavet property due to…

Functional Analysis · Mathematics 2025-07-15 Sheldon Dantas , Miguel Martín , Yoël Perreau

We demonstrate the result stated in the title, thus answering an open question asked by Julio Becerra Guerrero, Gin\'es L\'opez-P\'erez and Abraham Rueda Zoca in J. Conv. Anal. \textbf{25}, no. 3 (2018).

Functional Analysis · Mathematics 2021-09-13 Vladimir Kadets

Inspired by R. Whitley's thickness index the last named author recently introduced the Daugavet index of thickness of Banach spaces. We continue the investigation of the behavior of this index and also consider two new versions of the…

Functional Analysis · Mathematics 2020-05-18 Rainis Haller , Johann Langemets , Vegard Lima , Rihhard Nadel , Abraham Rueda Zoca

We study the Daugavet property in tensor products of Banach spaces. We show that $L_1(\mu)\widehat{\otimes}_\varepsilon L_1(\nu)$ has the Daugavet property when $\mu$ and $\nu$ are purely non-atomic measures. Also, we show that…

Functional Analysis · Mathematics 2019-03-06 Abraham Rueda Zoca , Pedro Tradacete , Ignacio Villanueva

We show that a Banach space with numerical index one cannot enjoy good convexity or smoothness properties unless it is one-dimensional. For instance, it has no WLUR points in its unit ball, its norm is not Frechet smooth and its dual norm…

Functional Analysis · Mathematics 2008-11-06 Vladimir Kadets , Miguel Martin , Javier Meri , Rafael Paya
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