Slightly adjusted Krein-Milman.

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Bokuan Li
2026-10-02 15:38:04 -04:00
parent 5e07b33c0d
commit 1bd178d7b3
+8 -9
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@@ -24,7 +24,7 @@
\begin{definition}[Extreme Point]
\label{definition:extreme-point}
Let $E$ be a vector space over $\real$, $K \subset E$, and $x \in K$, then $x$ is \textbf{extremal} if there exists no $y, z \in K$ such that $x \in (y, z) \subset K$.
Let $E$ be a vector space over $\real$, $K \subset E$, and $x \in K$, then $x$ is \textbf{extremal} if there exists no $y, z \in K \setminus \bracsn{x}$ such that $x \in (y, z) \subset K$.
\end{definition}
\begin{definition}[Extreme Subset]
@@ -32,6 +32,13 @@
Let $E$ be a vector space over $\real$, $K \subset E$ be convex, and $A \subset K$, then $A$ is \textbf{extreme set} if for any $x \in A$ and $y, z \in K$ such that $x \in (y, z)$, $y, z \in A$ as well.
\end{definition}
\begin{lemma}
\label{lemma:extreme-subset-extreme-point}
Let $E$ be a vector space over $\real$, $K \subset E$ be convex, $A \subset K$ be extreme, and $x \in A$ be an extreme point of $A$, then $x$ is an extreme point of $K$.
\end{lemma}
\begin{proof}
Let $y, z \in K$ such that $x \in (y, z)$. Since $A$ is extreme, $y, z \in A$. As $x$ is extremal in $A$, $x = y = z$, so $x$ is extremal in $K$.
\end{proof}
\begin{lemma}
\label{lemma:extremal-face}
@@ -135,11 +142,3 @@
Now, let $A'$ be the closed convex hull of $\seq{x_n}$ with respect to $E_B$. Since the inclusion $E_B \to E$ is continuous, $A'$ is a compact convex set in $E$ by \autoref{proposition:compact-extensions}. As such, $A' = A$ by \autoref{proposition:closure-of-image} and \autoref{proposition:compact-closed}. Therefore $A$ is a compact subset of $E_B$.
\end{proof}
\begin{lemma}
\label{lemma:auxiliary-weak-dense}
Let $E$ be a separated locally convex space over $K \in \RC$, $A \subset E$ be compact, convex, and circled, and $
\end{lemma}