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arXiv · 1506.05237

Diameter 2 properties and convexity

Trond A. Abrahamsen·Peter Hájek·Olav Nygaard·Jarno Talponen·Stanimir Troyanski
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Abstract

We present an equivalent midpoint locally uniformly rotund (MLUR) renorming $X$ of $C[0,1]$ on which every weakly compact projection $P$ satisfies the equation $\|I-P\| = 1+\|P\|$ ($I$ is the identity operator on $X$). As a consequence we obtain an MLUR space $X$ with the properties D2P, that every non-empty relatively weakly open subset of its unit ball $B_X$ has diameter 2, and the LD2P+, that for every slice of $B_X$ and every norm 1 element $x$ inside the slice there is another element $y$ inside the slice of distance as close to 2 from $x$ as desired. An example of an MLUR space with the D2P, the LD2P+, and with convex combinations of slices of arbitrary small diameter is also given.

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Trond A. Abrahamsen, Peter Hájek, Olav Nygaard, Jarno Talponen, Stanimir Troyanski. 2015-06-17. Diameter 2 properties and convexity. https://arxiv.org/abs/1506.05237

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