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arXiv 2508.18656math.FA
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可分Banach空间到$(\ell^\infty \setminus c)\cup\{0\}$的等距嵌入

Isometric embeddings of separable Banach spaces into $(\ell^\infty \setminus c)\cup\{0\}$

Geivison Ribeiro

AI总结:

该研究证明可分Banach空间可等距嵌入到与收敛序列空间$c$仅交于原点的$\ell^\infty$子集中,且相关可分子空间可保避开$c$的性质扩展为包含任意可分Banach空间等距副本的子空间,推广了经典嵌入结论。

摘要:

经典的Banach–Mazur定理断言,每个可分Banach空间都可等距嵌入到$C[0,1]$中。众所周知,每个可分Banach空间也可等距嵌入到$\ell^\infty$中。我们证明,可以选取这样的嵌入,使得其像与$c$的交集仅为原点。此外,我们证明,$(\ell^\infty \setminus c)\cup\{0\}$的任意有限维、可数维或更一般的可分子空间,都可以扩展为一个包含任意可分Banach空间的等距副本的子空间,同时仍避开$c$。我们进一步证明,该扩展性质对所有满足$D\cap c=\{0\}$且在商空间$\ell^\infty/c$中具有可分像的子空间$D\subset \ell^\infty$也成立。

英文摘要:

The classical Banach--Mazur theorem asserts that every separable Banach space admits an isometric embedding into $C[0,1]$. It is also well known that every separable Banach space embeds isometrically into $\ell^\infty$. We show that such an embedding can be chosen so that its image intersects $c$ only at the origin. Moreover, we prove that any finite- or countable-dimensional, or more generally separable, subspace of $(\ell^\infty \setminus c)\cup\{0\}$ can be extended to a subspace containing an isometric copy of an arbitrary separable Banach space, while still avoiding $c$. We further establish that this extension property also holds for every subspace $D\subset \ell^\infty$ with $D\cap c=\{0\}$ and separable image in the quotient $\ell^\infty/c$.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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