Polished A-A and added new lines for broken enumerates.
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Bokuan Li
2026-05-05 01:50:35 -04:00
parent 47a7e1de68
commit 0f2e69d1f9
81 changed files with 441 additions and 185 deletions

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@@ -21,12 +21,14 @@
\begin{enumerate}
\item[(a)] $\eta(y - Tx) \le \gamma \eta(y)$.
\item[(b)] $\rho(x) \le C \eta(y)$.
\end{enumerate}
\end\{enumerate\}
then for any $y \in F$, there exists $\seq{x_n} \subset E$ such that:
\begin{enumerate}
\item $\sum_{n \in \natp}\rho(x_n) \le C\eta(y)/(1 - \gamma)$.
\item $y = \limv{N}\sum_{n = 1}^N Tx_n$.
\end{enumerate}
\end\{enumerate\}
In particular,
\[
T\braks{B_E\paren{0, \frac{Cr}{(1 - \gamma)}}} \supset B_F(0, r)
@@ -38,12 +40,14 @@
\begin{enumerate}
\item[(I)] $\sum_{n = 1}^N\rho(x_n) \le C\eta(y)\sum_{n = 0}^{N-1}\gamma^{n}$.
\item[(II)] $\eta\paren{y - \sum_{n = 1}^N Tx_n} \le \eta(y)\gamma^N$.
\end{enumerate}
\end\{enumerate\}
By assumption, there exists $x_{N+1} \in E$ such that:
\begin{enumerate}
\item[(i)] $\eta\paren{y - \sum_{n = 1}^{N+1} Tx_n} \le \gamma \eta\paren{y - \sum_{n = 1}^N Tx_n} \le \gamma^{N+1}$.
\item[(ii)] $\rho(x_{N+1}) \le C\eta\paren{y - \sum_{n = 1}^N Tx_n} \le C\eta(y)\gamma^N$.
\end{enumerate}
\end\{enumerate\}
Combining (I) and (ii) shows that $\sum_{n = 1}^N \rho(x_n) \le C \eta(y) \sum_{n = 0}^N \gamma^n$. Therefore there exists $\seq{x_n} \subset E$ such that (I) and (II) holds for all $N \in \natp$.
By (I), $\sum_{n \in \natp}\rho(x_n) \le C\eta(y)\sum_{n \in \natz}\gamma^n = C \eta(y)/(1 - \gamma)$. By (II), $\limv{N}\eta\paren{y - \limv{N}\sum_{n = 1}^N Tx_n} = \limv{N}\eta(y)\gamma^N = 0$.
@@ -55,7 +59,8 @@
\begin{enumerate}
\item[(a)] For any $r > 0$, there exists $\delta(r) > 0$ such that $\overline{T(B_E(0, r))} \supset B_F(0, \delta(r))$.
\item[(b)] $E$ is complete.
\end{enumerate}
\end\{enumerate\}
then for every $s > r$, $T(B_E(0, s)) \supset B_F(0, \delta(r))$.
\end{proposition}
\begin{proof}
@@ -65,12 +70,14 @@
\item[(ii)] $s_1 = r$.
\item[(iii)] For all $n \in \natp$, $\overline{T(B_E(0, s_n))} \supset B_F(0, \delta_n)$.
\item[(iv)] $\rho_1 = \rho$.
\end{enumerate}
\end\{enumerate\}
Let $y_0 \in B(0, r)$ and $x_0 = 0$. Let $N \in \natp$ and suppose inductively that $\bracs{x_n}_1^N \subset E$ has been constructed such that:
\begin{enumerate}
\item[(I)] For each $0 \le n \le N - 1$, $\rho(x_{n+1} - x_n) < s_n$.
\item[(II)] For each $0 \le n \le N$, $\eta(Tx_n - y) \le \rho_{n+1}$.
\end{enumerate}
\end\{enumerate\}
By density of $T(x_N + B_E(0, s_N))$ in $Tx_N + B_F(0, \rho_N)$, there exists $x_{N+1} \in T(x_N + B_E(0, s_N))$ such that $\eta(Tx_{N+1} - y) \le \rho_{N+2}$.
By (I), $\seq{x_N}$ is a Cauchy sequence, so
@@ -88,7 +95,8 @@
\begin{enumerate}
\item[(a)] For any $r > 0$, there exists $C \ge 0$ such that for any $y \in T(E)$, there exits $x \in T^{-1}(y)$ with $\rho(x) \le C\eta(y)$.
\item[(b)] $E$ is complete.
\end{enumerate}
\end\{enumerate\}
then $T(E)$ is closed.
\end{proposition}
\begin{proof}

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@@ -8,11 +8,13 @@
\item $\wh E$ is a complete separated TVS.
\item $\iota \in L(E; \wh E)$.
\item[(U)] For any $(F, T)$ satisfying (1) and (2), there exists a unique $\ol{T} \in L(\wh E; F)$ such that the following diagram commutes:
\end{enumerate}
\end\{enumerate\}
Moreover,
\begin{enumerate}
\item[(4)] $\iota(E)$ is dense in $\wh E$.
\end{enumerate}
\end\{enumerate\}
The pair $(\wh E, \iota)$ is the \textbf{Hausdorff completion} of $E$.
\end{definition}
\begin{proof}

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@@ -9,7 +9,8 @@
\item $T \in UC(E; F)$.
\item $T \in C(E; F)$.
\item $T$ is continuous at $0$.
\end{enumerate}
\end\{enumerate\}
If the above holds, then $T$ is a \textbf{continuous linear map}. The set $L(E; F)$ denotes the vector space of all continuous linear maps from $E$ to $F$.
\end{definition}
\begin{proof}
@@ -48,7 +49,8 @@
}
\]
\end{enumerate}
\end\{enumerate\}
The uniformity $\fU$ and its induced topology are the \textbf{product uniformity/topology}, and $E$ equipped with $\fU$ is the \textbf{product TVS} of $\seqi{E}$.
\end{definition}

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@@ -8,7 +8,8 @@
\begin{enumerate}
\item[(TVS1)] $E \times E \to E$ with $(x, y) \mapsto x + y$ is continuous.
\item[(TVS2)] $K \times E \to E$ with $(\lambda, x) \mapsto \lambda x$ is continuous.
\end{enumerate}
\end\{enumerate\}
then the pair $(E, \topo)$ is a \textbf{topological vector space}.
\end{definition}
@@ -50,7 +51,8 @@
\begin{enumerate}
\item There exists a unique translation-invariant uniformity $\fU$ on $E$ that induces the topology on $E$.
\item For each neighbourhood $V \in \cn(0)$, let $U_V = \bracs{(x, y) \in E^2| x - y \in V}$, then for any fundamental system of neighbourhoods $\fB_0$ at $0$, $\fB = \bracs{U_V| V \in \fB_0}$ is a fundamental system of entourages for $\fU$.
\end{enumerate}
\end\{enumerate\}
The space $E$ will always be assumed to be equipped with its translation-invariant uniformity.
\end{proposition}
\begin{proof}
@@ -162,12 +164,14 @@
\begin{enumerate}
\item[(TVB1)] For each $U \in \fB$, there exists $V \in \fB$ such that $V + V \subset U$.
\item[(TVB2)] For each $U \in \fB$, $U$ is circled and radial.
\end{enumerate}
\end\{enumerate\}
Conversely, if $\fB \subset 2^E$ is a family of sets that contain $0$ and satisfies (TVB1) and (TVB2), then there exists a unique topology $\topo$ on $E$ such that:
\begin{enumerate}
\item $\topo$ is translation-invariant.
\item $\fB$ is a fundamental system of neighbourhoods at $0$ for $\topo$.
\end{enumerate}
\end\{enumerate\}
Moreover,
\begin{enumerate}
\item[(3)] $(E, \topo)$ is a TVS.
@@ -186,7 +190,8 @@
\item[(FB1)] For any $V, V' \in \fB$, there exists $W \in \fB$ with $W \subset V \cap V'$. In which case, $U_{V} \cap U_{V'} \supset U_W \in \mathfrak{V}$.
\item[(UB1)] For any $x \in E$ and $V \in \fB$, $x - x = 0 \in V$, so $\Delta \subset U_V$.
\item[(UB2)] For any $V \in \fB$, by (TVB1), there exists $W \in \fB$ such that $W + W \subset V$. In which case, for any $x, y, z \in E$ with $x - y, y - z \in W$, $x - z \in V$. Therefore $U_W \circ U_W \subset U_V$.
\end{enumerate}
\end\{enumerate\}
By \autoref{proposition:fundamental-entourage-criterion}, there exists a unique uniformity $\fU$ on $E$ for which $\mathfrak{V}$ is a fundamental system of entourages.
(1): Since $\mathfrak{V}$ is translation-invariant, so is $\fU$.

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@@ -7,7 +7,8 @@
\begin{enumerate}
\item $u \in \hom(E; \real)$ when $E$ is viewed as a vector space over $\real$.
\item For any $x \in E$, $\dpb{x, \phi}{E} = \dpb{x, u}{E} - i \dpb{ix, u}{E}$.
\end{enumerate}
\end\{enumerate\}
Conversely, if $u \in \hom(E; \real)$ and $\phi \in \hom(E; \complex)$ is defined by $\dpb{x, \phi}{E} = \dpb{x, u}{E} - i \dpb{ix, u}{E}$ for all $x \in E$, then $f \in \hom(E; \complex)$.
\end{proposition}
\begin{proof}[Proof {{\cite[Proposition 5.5]{Folland}}}. ]

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@@ -9,7 +9,8 @@
\item For each $i \in I$, $T_i \in L(E_i; E)$.
\item[(U)] For any topology $\mathcal{S}$ on $E$ satisfying (1) and (2), $\mathcal{S} \subset T$.
\item For any TVS $F$ and $T \in \hom(E; F)$, $T \in L(E; F)$ if and only if $T \circ T_i \in L(E_i; F)$ for all $i \in I$.
\end{enumerate}
\end\{enumerate\}
The topology $\topo$ is the \textbf{inductive topology} on $E$ induced by $\seqi{T}$.
\end{definition}
\begin{proof}
@@ -61,7 +62,8 @@
for all $i \in I$.
\item For any TVS $F$ and $T \in \hom(E; F)$, $T \in L(E; F)$ if and only if $T \circ T^i_E \in L(E_i; F)$ for all $i \in I$.
\end{enumerate}
\end\{enumerate\}
The pair $(E, \bracsn{T^i_E}_{i \in I})$ is the \textbf{inductive limit} of $(\seqi{E}, \bracsn{T^i_j| i, j \in I, i \lesssim j})$.
\end{definition}
\begin{proof}

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@@ -82,7 +82,8 @@
\begin{enumerate}
\item[(a)] For each $n \in \natp$, $U_n$ is circled, radial, and contains $0$.
\item[(b)] For each $n \in \natp$, $U_{n+1} + U_{n+1} \subset U_n$.
\end{enumerate}
\end\{enumerate\}
then there exists a pseudonorm $\rho: E \to [0, \infty)$ such that for each $n \in \natp$,
\[
U_{n+1} \subset \rho^{-1}([0, 2^{-n})) \subset U_{n}
@@ -110,7 +111,8 @@
so $\rho(\lambda x) \le \rho(x)$.
\item[(PN3)] Let $x, y \in X$ and $M, N \subset \natp$ finite such that $x \in U_M$ and $y \in U_N$. Assume without loss of generality that $\rho_M + \rho_N < 1$, then there exists a unique $P \subset \nat$ finite such that $\rho_P = \rho_M + \rho_N$. In which case, $U_P \supset U_M + U_N$ by assumption (b). Therefore $\rho(x + y) \le \rho(x) + \rho(y)$.
\end{enumerate}
\end\{enumerate\}
For any $x \in U_{n+1}$, $\rho(x) \le 2^{-n+1} < 2^n$, so $U_{n+1} \subset \rho^{-1}([0, 2^{-n}))$ by \autoref{proposition:dyadic-semigroup-order}. On the other hand, for any $x \in E$ with $\rho(x) < 2^{-n}$, $x \in U_{2^{-n}} = U_n$. This allows showing the remaining seminorm axioms by considering neighbourhoods of the form $\bracs{U_n|n \in \natp}$.
\begin{enumerate}
\item[(PN4)] Let $x \in X$ and $n \in \natp$. By assumption (a), there exists $\alpha > 0$ such that for any $\lambda \in K$ with $\abs{\lambda} \ge \alpha$, $x \in \lambda U_n$. Therefore for any $\lambda \in K$ with $\abs{\lambda} \le \alpha^{-1}$, $\lambda x \in U_n$, and $\rho(x) \le 2^{-n}$.

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@@ -7,7 +7,8 @@
\begin{enumerate}
\item For each $i \in I$, $T_i \in L(E; F_i)$.
\item[(U)] If $\mathfrak{V}$ is a uniformity on $E$ satisfying $(1)$, then $\mathfrak{V} \supset \fU$.
\end{enumerate}
\end\{enumerate\}
Moreover,
\begin{enumerate}
\item[(3)] $\fU$ is translation-invariant.
@@ -19,7 +20,8 @@
\]
is a fundamental system of neighbourhoods for $E$ at $0$.
\end{enumerate}
\end\{enumerate\}
The uniformity $\fU$ and its topology are the \textbf{projective uniformity/topology} induced by $\seqi{T}$.
\end{definition}
@@ -74,7 +76,8 @@
for all $i \in I$.
\item For any TVS $F$ over $K$ and $S \in \hom(F; E)$, $S \in L(F; E)$ if and only if $T^E_i \circ S \in L(F; E_i)$ for all $i \in I$.
\end{enumerate}
\end\{enumerate\}
The pair $(E, \bracsn{T^E_i}_{i \in I})$ is the \textbf{projective limit} of $(\seqi{E}, \bracsn{T^i_j|i, j \in I, i \lesssim j})$.
\end{definition}
\begin{proof}

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@@ -17,7 +17,8 @@
\]
If $F$ is a TVS over $K$ and $f \in L(E; F)$, then $\td f \in L(E; F)$.
\end{enumerate}
\end\{enumerate\}
The space $\td E = E/M$ is the \textbf{quotient} of $E$ by $M$.
\end{definition}
\begin{proof}
@@ -32,7 +33,8 @@
\begin{enumerate}
\item[(TVB1)] Let $U \in \cn(0)$ be circled and radial. For any $\lambda \in K$ with $\abs{\lambda} \le 1$, $\lambda \pi(U) = \pi(\lambda U) \subset \pi(U)$, so $\pi(U)$ is also circled. For any $x + M \in E/M$, there exists $\lambda \in K$ such that $x \in \lambda U$. In which case, $x \in \lambda U + M = \pi(U)$, so $\pi(U)$ is also radial.
\item[(TVB2)] For any $U \in \cn(0)$ circled and radial, by \autoref{proposition:tvs-good-neighbourhood-base}, there exists $W \in \cn(0)$ such that $W + W \subset U$. In which case, $\pi(W) + \pi(W) \subset \pi(U)$.
\end{enumerate}
\end\{enumerate\}
By \autoref{proposition:tvs-0-neighbourhood-base}, there exists a unique translation-invariant topology on $E/M$ such that $\fB$ is a fundamental system of neighbourhoods at $0$, which must be the quotient topology on $E/M$. In which case, the quotient topology is a vector space topology by (3) of \autoref{proposition:tvs-0-neighbourhood-base}.
(2), (3), (U): By \autoref{definition:quotient-topology}.

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@@ -115,7 +115,8 @@
\]
is an isomorphism.
\end{enumerate}
\end\{enumerate\}
which allows the identification
\[
\underbrace{B_{\sigma}(E; B_{\sigma}(E; \cdots)))}_{k \text{ times}} = B^k_{\sigma}(E; F)
@@ -166,7 +167,8 @@
\begin{enumerate}
\item[(a)] There exists a dense subset $S \subset E$ such that $T_\alpha x \to Tx$ strongly for all $x \in S$.
\item[(b)] $\bracs{T_\alpha|\alpha \in A}$ is uniformly equicontinuous.
\end{enumerate}
\end\{enumerate\}
then $T_\alpha \to T$ in $L_s(E; F)$.
\end{proposition}