From 8c090f3c932482f1997fbfb589a4e7461b78dfb3 Mon Sep 17 00:00:00 2001 From: Bokuan Li Date: Tue, 22 Sep 2026 10:38:12 -0400 Subject: [PATCH] Slight adjustments. --- src/op/example/bounded.tex | 16 ++++++++++++++++ src/topology/main/compactify.tex | 4 ++-- 2 files changed, 18 insertions(+), 2 deletions(-) diff --git a/src/op/example/bounded.tex b/src/op/example/bounded.tex index f01ad7e..7733455 100644 --- a/src/op/example/bounded.tex +++ b/src/op/example/bounded.tex @@ -6,6 +6,22 @@ Let $H$ be a complex Hilbert space, then $B(H) = L(H; H)$ is the algebra of all bounded linear operators on $H$. \end{definition} +\begin{lemma} +\label{lemma:unitary-ots} + Let $H$ be a complex Hilbert space, then the strong and weak operator topologies on $U(B(H))$ coincide. +\end{lemma} +\begin{proof} + Let $S, T \in U(B(H))$ and $\xi \in H$, then + \begin{align*} + \norm{(S - T)\xi}_H^2 &= \dpn{(S - T)\xi, (S - T)\xi}{H} \\ + &= \norm{S\xi}_H^2 + \norm{T\xi}_H^2 - 2\text{Re}\angles{S\xi, T\xi}_H \\ + &= 2\norm{\xi}_H^2 - 2\text{Re}\angles{S\xi, T\xi}_H + \end{align*} + + which tends to $0$ as $S \to T$ in the weak operator topology. + +\end{proof} + % 1. Every non-trivial ideal of B(H) contains the finite-rank operators. % 2. If H is separable, then the only non-trivial closed idela of B(H) are the compact operators. diff --git a/src/topology/main/compactify.tex b/src/topology/main/compactify.tex index f3dffd3..b331eeb 100644 --- a/src/topology/main/compactify.tex +++ b/src/topology/main/compactify.tex @@ -143,7 +143,7 @@ The pair $(X^*, \iota)$ is the \textbf{one-point compactification} of $X$. \end{definition} \begin{proof} - Let $\infty$ be a point not in $X$, $X^* = X \sqcup \bracs{\infty}$, and $\mathcal{T}^* \subset 2^{X^*}$ such that for each $U \in \mathcal{T}^*$, one of the following holds: + (1): Let $\infty$ be a point not in $X$, $X^* = X \sqcup \bracs{\infty}$, and $\mathcal{T}^* \subset 2^{X^*}$ such that for each $U \in \mathcal{T}^*$, one of the following holds: \begin{enumerate}[label=(\alph*)] \item $U \in \mathcal{T}$. \item $\infty \in U$ and $U^c \subset X$ is compact. @@ -153,7 +153,7 @@ Let $\iota: X \to X^*$ be the inclusion map. For each $U \in \mathcal{T}^*$ satisfying (b), $\iota^{-1}(U) = U \cap X$. Since $U^c \subset X$ is compact, $U \cap X$ is open by \autoref{proposition:compact-closed}, so $\iota \in C(X; X^*)$. By (a), $\iota$ is an embedding. - Finally, let + (U): Let \[ \varphi^*: Y \to X^* \quad x \mapsto \begin{cases} \varphi^{-1}(x) &x \in \varphi(X) \\