Added path lemma.
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Bokuan Li
2026-05-27 22:59:06 -04:00
parent 5923b45f9d
commit 02bd8479bc
6 changed files with 93 additions and 2 deletions

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@@ -7,6 +7,10 @@
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"task": "Conservative"
},
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"label": "Compile All",
"task": "Build"
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],
"latex.linting.enabled": false,

2
.vscode/tasks.json vendored
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@@ -4,7 +4,7 @@
{
"label": "Build",
"type": "shell",
"command": "npx spec compile",
"command": "npx spec compile --all",
"windows": {
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@@ -280,5 +280,63 @@
(5) $\Rightarrow$ (3): By the equivalence of the prior points, for any $\phi \in E^*$, $\phi \circ f$ satisfies (3). By the \hyperref[Hahn-Banach Theorem]{proposition:hahn-banach-utility}, $f$ also satisfies (3).
\end{proof}
\begin{proposition}
\label{proposition:existence-curves}
Let $K \subset \complex$ be compact and $U \in \cn_\complex(K)$, then there exists closed rectifiable curves $\seqf{\gamma_j}$ such that for any separated locally convex space $E$, $f \in H(U; E)$, and $z_0 \in K$,
\[
f(z) = \sum_{j = 1}^n \int_{\gamma_j} \frac{f(z)}{z - z_0}dz
\]
\end{proposition}
\begin{proof}[Proof, {{\cite[Proposition VIII.1.1]{ConwayComplex}}}. ]
Via \hyperref[fattening]{proposition:distance-compact}, let $V \in \cn_\complex^o(K)$ precompact with $\ol V \subset U$. Identify $\complex = \real^2$, then since $V$ is precompact, there exists $\delta > 0$ and $\seqf{(x_j, y_j)} \subset U$ such that:
\begin{enumerate}
\item For each $1 \le j \le n$, $R_j = [x_j, x_j + \delta] \times [y_j, y_j + \delta] \subset U$.
\item $\bigcup_{j = 1}^n R_j \supset V$.
\item $x_j, y_j = 0 \mod \delta$.
\end{enumerate}
In other words, $V$ is covered with a grid of squares with side-length $\delta$ and corners $\seqf{(x_j, y_j)}$. Now, for each $1 \le j \le n$ and $t \in [0, 1]$, let
\begin{align*}
\gamma_{j, \rightarrow}(t) &= (1 - t)(x_j, y_j) + t(x_j + \delta, y_j) \\
\gamma_{j, \uparrow}(t) &= (1 - t)(x_j + \delta, y_j) + t(x_j + \delta, y_j + \delta) \\
\gamma_{j, \leftarrow}(t) &= (1 - t)(x_j + \delta, y_j + \delta) + t(x_j, y_j + \delta) \\
\gamma_{j, \downarrow}(t) &= (1 - t)(x_j, y_j + \delta) + t(x_j, y_j) \\
\end{align*}
and $\gamma_j = \gamma_{j, \downarrow} \cdot \gamma_{j, \leftarrow} \cdot \gamma_{j, \uparrow} \cdot \gamma_{j, \rightarrow}$ be their concatenation, then for each $z \in U \setminus \partial R_j$,
\[
\int_{\gamma_j} \frac{f(z)}{z - z_0}dz = \begin{cases}
f(z) &z \in R_j^o \\
0 &z \in U \setminus R_j
\end{cases}
\]
by \hyperref[Cauchy's Integral Formula]{theorem:cauchy-formula}. Let $\seqf[N]{\mu_j}$ be an enumeration of
\[
\bigcup_{j = 1}^n \bracs{\gamma_{j, \downarrow}, \gamma_{j, \leftarrow}, \gamma_{j, \uparrow}, \gamma_{j, \rightarrow}}
\]
then for each $z_0 \in \bigcup_{j = 1}^n R_j^o$ and $f \in H(U; E)$,
\[
f(z) = \sum_{j = 1}^N \int_{\mu_j}\frac{f(z)}{z - z_0}dz
\]
From here, it is sufficient to eliminate line segments that intersect $K$ and ensure that the remaining segments form a collection of loops. Let $1 \le j \le k \le N$, then $(\mu_j, \mu_k)$ is \textit{redundant} if for each $t \in [0, 1]$, $\mu_j(t) = \mu_k(1 - t)$. If $(\mu_j, \mu_k)$ are redundant, then
\begin{enumerate}[start=3]
\item There exists no $1 \le l \le N$ with $l \ne j, k$ such that $(\mu_j, \mu_l)$ or $(\mu_k, \mu_l)$ is redundant.
\item $\int_{\mu_j}\frac{f(z)}{z - z_0}dz + \int_{\mu_k}\frac{f(z)}{z - z_0}dz = 0$.
\end{enumerate}
so every line segment either cannot form a redundant pair, or forms a unique one.
By relabeling, let $\bracs{\mu_j|1 \le j \le m}$ such that for each $1 \le j \le m$, there exists no $1 \le k \le n$ such that $(\mu_j, \mu_k)$ is redundant. By (5), for each $z_0 \in \bigcup_{j = 1}^n R_j^o$ and $f \in H(U; E)$,
\[
f(z) = \sum_{j = 1}^m \int_{\mu_j}\frac{f(z)}{z - z_0}dz
\]
Let $1 \le j \le N$ such that $\mu_j([0, 1]) \cap K \ne \emptyset$. Since $V \in \cn_\complex(K)$, there exists $1 \le k \le N$ such that $(\mu_j, \mu_k)$ are redundant by (2) and (3). Therefore $\bigcup_{j = 1}^m \mu_j([0, 1]) \cap K = \emptyset$. Since $\bigcup_{j = 1}^n R_j^o$ is dense in $K$, the above also holds for all $z \in K$.
Finally, let $1 \le j \le m$. Since $\mu_j$ does not form a redundant pair, $\mu_j(1)$ intersects at most two distinct squares by (3). In which case, there must exist $1 \le k \le m$ such that $\mu_k(0) = \mu_j(1)$. Therefore $\seqf[m]{\mu_j}$ forms a collection of closed rectifiable curves.
\end{proof}

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@@ -38,3 +38,15 @@
(C1) $\Leftrightarrow$ (C2): By the \hyperref[Arzelà-Ascoli Theorem]{theorem:arzela-ascoli}.
\end{proof}
\begin{definition}[Space of Holomorphic Functions Near a Set]
\label{definition:holomorphic-function-space-near}
Let $E$ be a complete separated locally convex space over $\complex$ and $A \subset \complex$. Direct $\cn_{\complex}^o(A)$ under reverse inclusion, then the inductive limit
\[
H(A; E) = \varinjlim_{U \in \cn_{\complex}^o(A)} H(U; E)
\]
is the \textbf{space of holomorphic functions near} $A$, and is of type (LF).
\end{definition}

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@@ -186,7 +186,7 @@
\begin{definition}[Locally Convex Space]
\label{definition:locally-convex}
Let $E$ be a TVS over $\RC$, then the following are equivalent:
Let $E$ be a TVS over $K \in \RC$, then the following are equivalent:
\begin{enumerate}
\item There exists a fundamental system of neighborhoods at $0$ consisting of convex sets.
\item There exists a fundamental system of neighbourhoods at $0$ consisting of convex, circled, and radial sets.
@@ -203,6 +203,10 @@
$(3) \Rightarrow (1)$: For each $i \in I$ and $r > 0$, $\bracs{x \in E| [x]_i < r}$ is convex.
\end{proof}
\begin{definition}[Fréchet Space]
\label{definition:frechet-space}
Let $E$ be a locally convex space over $K \in \RC$, then $E$ is a \textbf{Fréchet space} if $E$ is first countable and complete.
\end{definition}
\begin{definition}[Associated Normed Space]

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@@ -268,3 +268,16 @@
which contradicts the fact that $(F_n + U) \cap E_n = \emptyset$.
\end{proof}
\begin{definition}[Space of Type (LB)]
\label{definition:lb-space}
Let $E$ be a locally convex space, then $E$ is of type \textbf{(LB)} if $E$ is the strict inductive limit of a countable system of Banach spaces.
\end{definition}
\begin{definition}[Space of Type (LF)]
\label{definition:lf-space}
Let $E$ be a locally convex space, then $E$ is of type \textbf{(LF)} if $E$ is the strict inductive limit of a countable system of Fréchet spaces.
\end{definition}