ℓ_1-preduals的显式模型和ℓ_1中的弱*定点性质

Pub Date : 2024-03-10 DOI:10.12775/tmna.2023.009
E. Casini, E. Miglierina, Łukasz Piasecki
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引用次数: 0

摘要

我们对$\ell_1$的所有前元进行了具体的等距描述,对于这些前元,$\ell_1$的标准基础有有限个$w^*$极限点。然后,我们应用这一结果给出一个$\ell_1$前元$X$的例子,其对偶$X^*$缺乏非展开映射的弱$^*$定点性质(简言之,$w^*$-FPP)、但是 $X$ 不包含收敛序列空间 $c$ 的任何超平面 $W_{\alpha}$ 的等距副本,使得 $W_\alpha$ 是 $\ell_1$ 的前元,并且 $W_\alpha^*$ 缺乏 $w^*$-FPP.这回答了本文作者 2017 年论文中的一个未决问题。
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Explicit models of ℓ_1-preduals and the weak* fixed point property in ℓ_1
We provide a concrete isometric description of all the preduals of $\ell_1$ for which the standard basis in $\ell_1$ has a finite number of $w^*$-limit points. Then, we apply this result to give an example of an $\ell_1$-predual $X$ such that its dual $X^*$ lacks the weak$^*$ fixed point property for nonexpansive mappings (briefly, $w^*$-FPP), but $X$ does not contain an isometric copy of any hyperplane $W_{\alpha}$ of the space $c$ of convergent sequences such that $W_\alpha$ is a predual of $\ell_1$ and $W_\alpha^*$ lacks the $w^*$-FPP. This answers a question left open in the 2017 paper of the present authors.
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