fixed some typos; currying

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Josia Pietsch 2024-02-05 15:07:13 +01:00
parent c9212aefdd
commit f4d64527c4
Signed by: josia
GPG key ID: E70B571D66986A2D
5 changed files with 16 additions and 16 deletions

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@ -185,11 +185,11 @@ suffices to show that open balls in one metric are unions of open balls in the o
\begin{definition}[Our favourite Polish spaces]
\leavevmode
\begin{itemize}
\item $2^{\omega}$ is called the \vocab{Cantor set}.
\item $2^{\N}$ is called the \vocab{Cantor set}.
(Consider $2$ with the discrete topology)
\item $\omega^{\omega}$ is called the \vocab{Baire space}.
($\omega$ with descrete topology)
\item $[0,1]^{\omega}$ is called the \vocab{Hilbert cube}.
\item $\cN \coloneqq \N^{\N}$ is called the \vocab{Baire space}.
($\N$ with descrete topology)
\item $\mathbb{H} \coloneqq [0,1]^{\N}$ is called the \vocab{Hilbert cube}.
($[0,1] \subseteq \R$ with the usual topology)
\end{itemize}
\end{definition}

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@ -78,18 +78,17 @@ where $X$ is a metrizable, usually second countable space.
we also have
$A = \bigcup_n A_n'$ with $A'_n \in \Pi^0_{\xi_n}(X)$.
We construct a $(2^\omega)^\omega \cong 2^\omega$-universal set
We construct a $(2^{\omega \times \omega}) \cong 2^\omega$-universal set
for $\Sigma^0_\xi(X)$.
For $(y_n) \in (2^\omega)^\omega$
For $(y_{m,n}) \in (2^{\omega \times \omega})$
and $x \in X$
we set $((y_n), x) \in \cU$
iff $\exists n.~(y_n, x) \in U_{\xi_n}$,
i.e.~iff $\exists n.~x \in (U_{\xi_n})_{y_n}$.
we set $((y_{m,n}), x) \in \cU$
iff $\exists n.~((y_{m,n})_{m < \omega}, x) \in U_{\xi_n}$,
i.e.~iff $\exists n.~x \in (U_{\xi_n})_{(y_{m,n})_{m < \omega}}$.
Let $A \in \Sigma^0_\xi(X)$.
Then $A = \bigcup_{n} B_n$ for some $B_n \in \Pi^0_{\xi_n}(X)$.
% TODO
Furthermore $\cU \in \Sigma^0_{\xi}((2^\omega)^\omega \times X)$.
Furthermore $\cU \in \Sigma^0_{\xi}((2^{\omega \times \omega} \times X)$.
\end{proof}
\begin{remark}
Since $2^{\omega}$ embeds

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@ -34,7 +34,8 @@ we need the following definition:
\begin{lemma}
\label{lem:lusinsephelp}
If $P = \bigcup_{m < \omega} P_m$, $Q = \bigcup_{n < \omega} Q_n$ are such that
for any $m, n$ the sets $P_m$ and $Q_n$ are Borel separable.
for any $m, n$ the sets $P_m$ and $Q_n$ are Borel separable,
then $P$ and $Q$ are Borel separable.
\end{lemma}
\begin{proof}
For all $m, n$ pick $R_{m,n}$ Borel,
@ -42,7 +43,7 @@ we need the following definition:
and $Q_n \cap R_{m,n} = \emptyset$.
Then $R = \bigcup_m \bigcap_n R_{m,n}$
has the desired property
that $R \subseteq R$ and $R \cap Q = \emptyset$.
that $P \subseteq R$ and $R \cap Q = \emptyset$.
\end{proof}
\begin{notation}
@ -60,7 +61,7 @@ we need the following definition:
Write $A_s \coloneqq f(\cN_s)$ and $B_s \coloneqq g(\cN_s)$.
Note that $A_s = \bigcup_m A_{s\concat m}$
and $B_ns = \bigcup_{n < \omega} B_{s\concat n}$.
and $B_s = \bigcup_{n < \omega} B_{s\concat n}$.
In particular
$A = \bigcup_{m < \omega} A_{\underbrace{\langle m \rangle}_{\in \omega^1}}$

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@ -183,7 +183,7 @@ i.e.}{}
Let $X$ be Polish and $C \subseteq X$ coanalytic.
Then $\phi\colon C \to \Ord$
is a \vocab[Rank!$\Pi^1_1$-rank]{$\Pi^1_1$-rank}
provided that $\le^\ast$ and $<^\ast$ are coanalytic subsets of $X \times X$,
provided that $\le^\ast_\phi$ and $<^\ast_\phi$ are coanalytic subsets of $X \times X$,
where
$x \le^\ast_{\phi} y$
iff

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@ -55,7 +55,7 @@
then $\xi = \alpha$
and
\[
E_\xi = E_\alpha = \bigcup_{\eta < \alpha}
E_\xi = E_\alpha = \bigcup_{\eta < \alpha} E_\eta
\]
is a countable union of Borel sets by the previous case.
\end{itemize}