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Idonknow
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Is it true that every Banach space has at least one extreme functionalpoint that is normed by some point?

Definition: Let $X$ be a Banach space. and $X^*$ be its continuous dual of $X,$ that is, $X^*$ contains all bounded linear functionals on $X.$ Denote $$B_{X^*} = \{x^*\in X^*: \|x^*\|_{X^*}\leq 1\}.$$ We say that a bounded linear functional $x^*:X\to \mathbb{R}$$x^*\in B_{X^*}$ is an extreme point of $B_X = \{x\in X:\|x\|_X\le 1\}$$B_{X^*}$ if whenever $$x^* = \frac{1}{2}(y_1^*+y_2^*)$$ for some $y_1^*,y_2^*$ with $\|y_i^*\|_{X^*} \leq 1$ for all $i=1,2,$ we have $x^* = y_1^*=y_2^*.$


Question: Given a Banach space $X.$ Is it true that there exists an bounded linear extreme functionalpoint $x^*:X\to\mathbb{R}$$x^*$ of $B_{X^*}$ such that $$x^*(x) = 1$$ for some $x\in X$ with $\|x\|\leq 1?$

In other words, is it true that every Banach space has at least one extreme functionalpoint that is normed by some point?

Is it true that every Banach space has at least one extreme functional that is normed by some point?

Definition: Let $X$ be a Banach space. We say that a bounded linear functional $x^*:X\to \mathbb{R}$ is an extreme point of $B_X = \{x\in X:\|x\|_X\le 1\}$ if whenever $$x^* = \frac{1}{2}(y_1^*+y_2^*)$$ for some $y_1^*,y_2^*$ with $\|y_i^*\|_{X^*} \leq 1$ for all $i=1,2,$ we have $x^* = y_1^*=y_2^*.$


Question: Given a Banach space $X.$ Is it true that there exists an bounded linear extreme functional $x^*:X\to\mathbb{R}$ such that $$x^*(x) = 1$$ for some $x\in X$ with $\|x\|\leq 1?$

In other words, is it true that every Banach space has at least one extreme functional that is normed by some point?

Is it true that every Banach space has at least one extreme point that is normed by some point?

Definition: Let $X$ be a Banach space and $X^*$ be its continuous dual of $X,$ that is, $X^*$ contains all bounded linear functionals on $X.$ Denote $$B_{X^*} = \{x^*\in X^*: \|x^*\|_{X^*}\leq 1\}.$$ We say that $x^*\in B_{X^*}$ is an extreme point of $B_{X^*}$ if whenever $$x^* = \frac{1}{2}(y_1^*+y_2^*)$$ for some $y_1^*,y_2^*$ with $\|y_i^*\|_{X^*} \leq 1$ for all $i=1,2,$ we have $x^* = y_1^*=y_2^*.$


Question: Given a Banach space $X.$ Is it true that there exists an extreme point $x^*$ of $B_{X^*}$ such that $$x^*(x) = 1$$ for some $x\in X$ with $\|x\|\leq 1?$

In other words, is it true that every Banach space has at least one extreme point that is normed by some point?

Source Link
Idonknow
  • 623
  • 5
  • 14

Is it true that every Banach space has at least one extreme functional that is normed by some point?

Definition: Let $X$ be a Banach space. We say that a bounded linear functional $x^*:X\to \mathbb{R}$ is an extreme point of $B_X = \{x\in X:\|x\|_X\le 1\}$ if whenever $$x^* = \frac{1}{2}(y_1^*+y_2^*)$$ for some $y_1^*,y_2^*$ with $\|y_i^*\|_{X^*} \leq 1$ for all $i=1,2,$ we have $x^* = y_1^*=y_2^*.$


Question: Given a Banach space $X.$ Is it true that there exists an bounded linear extreme functional $x^*:X\to\mathbb{R}$ such that $$x^*(x) = 1$$ for some $x\in X$ with $\|x\|\leq 1?$

In other words, is it true that every Banach space has at least one extreme functional that is normed by some point?