From 47145cdf582b59f5f7afcf74ba953655776506c4 Mon Sep 17 00:00:00 2001 From: Bokuan Li Date: Sat, 30 May 2026 20:40:38 -0400 Subject: [PATCH] Adjusted labeling of conditions for Banach-Steinhaus. --- src/fa/norm/normed.tex | 4 ++-- src/fa/tvs/equicontinuous.tex | 10 +++++----- 2 files changed, 7 insertions(+), 7 deletions(-) diff --git a/src/fa/norm/normed.tex b/src/fa/norm/normed.tex index b007971..ce258d2 100644 --- a/src/fa/norm/normed.tex +++ b/src/fa/norm/normed.tex @@ -73,8 +73,8 @@ \label{theorem:uniform-boundedness} Let $E, F$ be normed vector spaces and $\mathcal{T} \subset L(E; F)$. If \begin{enumerate} - \item[(B)] $E$ is a Banach space. - \item[(E2)] For every $x \in E$, $\sup_{T \in \mathcal{T}}\norm{Tx}_F < \infty$. + \item[(B1)] $E$ is a Banach space. + \item[(B2)] For every $x \in E$, $\sup_{T \in \mathcal{T}}\norm{Tx}_F < \infty$. \end{enumerate} then $\sup_{T \in \mathcal{T}}\norm{T}_{L(E; F)} < \infty$. diff --git a/src/fa/tvs/equicontinuous.tex b/src/fa/tvs/equicontinuous.tex index 9ce5a65..d728fae 100644 --- a/src/fa/tvs/equicontinuous.tex +++ b/src/fa/tvs/equicontinuous.tex @@ -37,13 +37,13 @@ \label{theorem:banach-steinhaus} Let $E, F$ be TVSs over $K \in \RC$ and $\alg \subset L(E; F)$. Suppose that one of the following holds: \begin{enumerate} - \item[(B)] $E$ is a Baire space. - \item[(B')] $E$ is barrelled and $F$ is locally convex. + \item[(B1)] $E$ is a Baire space. + \item[(B1')] $E$ is barrelled and $F$ is locally convex. \end{enumerate} and that \begin{enumerate} - \item[(E2)] For each $x \in E$, $\alg(x) = \bracs{Tx|T \in \alg}$ is bounded in $F$. + \item[(B2')] For each $x \in E$, $\alg(x) = \bracs{Tx|T \in \alg}$ is bounded in $F$. \end{enumerate} then @@ -54,14 +54,14 @@ \end{enumerate} \end{theorem} \begin{proof}[Proof, {{\cite[IV.4.2]{SchaeferWolff}}}. ] - (B) + (E2) $\Rightarrow$ (E1): Let $V \in \cn_F(0)$ be closed and circled, then $U = \bigcap_{T \in \alg}T^{-1}(V)$ is circled and closed. By (E2), $U$ is absorbing, so $E = \bigcup_{n \in \natp}nU$. Since $E$ is Baire, there exists $n \in \natp$, $W \in \cn_E(0)$, and $x \in E$ such that $x + W \subset nU$. As $U$ is circled, + (B1) + (B2) $\Rightarrow$ (E1): Let $V \in \cn_F(0)$ be closed and circled, then $U = \bigcap_{T \in \alg}T^{-1}(V)$ is circled and closed. By (B2), $U$ is absorbing, so $E = \bigcup_{n \in \natp}nU$. Since $E$ is Baire, there exists $n \in \natp$, $W \in \cn_E(0)$, and $x \in E$ such that $x + W \subset nU$. As $U$ is circled, \[ W \subset nU - nU = nU + nU = 2nU \] so $U \in \cn_E(0)$, and $\alg$ is equicontinuous by \autoref{proposition:equicontinuous-linear}. - (B') + (E2) $\Rightarrow$ (E1): Let $V \in \cn_F(0)$ be convex, circled, and closed, then $U = \bigcap_{T \in \alg}T^{-1}(V)$ is convex, circled, and closed. By (E2), $U$ is absorbing, and hence a barrel in $E$. By (B'), $U \in \cn_E(0)$, $\alg$ is equicontinuous by \autoref{proposition:equicontinuous-linear}. + (B1') + (B2) $\Rightarrow$ (E1): Let $V \in \cn_F(0)$ be convex, circled, and closed, then $U = \bigcap_{T \in \alg}T^{-1}(V)$ is convex, circled, and closed. By (B2), $U$ is absorbing, and hence a barrel in $E$. By (B1'), $U \in \cn_E(0)$, $\alg$ is equicontinuous by \autoref{proposition:equicontinuous-linear}. (E1) $\Rightarrow$ (C1) + (C2): By the \hyperref[ArzelĂ -Ascoli Theorem]{theorem:arzela-ascoli} and \autoref{proposition:equicontinuous-linear-closure}. \end{proof}