Questions regarding the Hahn-Banach Theorem.
This tag is aimed for questions regarding the Hahn-Banach Theorem and functional analysis topics over its consequences.
Questions tagged [hahn-banach-theorem]
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Norm supremum of unit-dual elements w/o Hahn-Banach
Let X be a a separable Banach space. I have to prove that for every $x \in X$ there exists a sequence $\{x_n^*\}_{n \in \mathbb{N}} \subseteq \overline{B}_1^{X^*} = \{x^* \in X^*: \|x^*\|_* \leq 1\}$ such that
$$ \|x\| = \sup _{n \in \mathbb{N}}…
Duncan Idaho
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