论文标题

$ \ ell_p(γ)$和操作员范围的密集子空间中的平滑规范

Smooth norms in dense subspaces of $\ell_p(Γ)$ and operator ranges

论文作者

Dantas, Sheldon, Hájek, Petr, Russo, Tommaso

论文摘要

For $1\leq p<\infty$, we prove that the dense subspace $\mathcal{Y}_p$ of $\ell_p(Γ)$ comprising all elements $y$ such that $y \in \ell_q(Γ)$ for some $q \in (0,p)$ admits a $C^{\infty}$-smooth norm which locally depends on finitely many坐标。此外,可以选择这样的规范以近似$ \ weled \ vert \ cdot \ right \ vert_p $ -norm。这提供了具有平滑标准的$ \ ell_p(γ)$的密集子空间的示例,具有最大可能的线性维度,并且不能作为生物息肉系统的线性跨度获得。此外,当$ p> 1 $或$γ$可数时,此类子空间还包含密集的操作员范围;另一方面,$ \ ell_1(γ)$中没有不可分割的操作员范围允许$ c^1 $ -SMOOTH NORM。

For $1\leq p<\infty$, we prove that the dense subspace $\mathcal{Y}_p$ of $\ell_p(Γ)$ comprising all elements $y$ such that $y \in \ell_q(Γ)$ for some $q \in (0,p)$ admits a $C^{\infty}$-smooth norm which locally depends on finitely many coordinates. Moreover, such a norm can be chosen as to approximate the $\left\Vert\cdot \right\Vert_p $-norm. This provides examples of dense subspaces of $\ell_p(Γ)$ with a smooth norm which have the maximal possible linear dimension and are not obtained as the linear span of a biorthogonal system. Moreover, when $p>1$ or $Γ$ is countable, such subspaces additionally contain dense operator ranges; on the other hand, no non-separable operator range in $\ell_1(Γ)$ admits a $C^1$-smooth norm.

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