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dfd9be7925
reference to sheet 11
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2024-02-04 13:38:53 +01:00
236874b1a5
some small changes 2024-02-04 01:36:10 +01:00
3 changed files with 6 additions and 5 deletions

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@ -199,8 +199,8 @@
\[ \[
D \subseteq \N^\N \mathbin{\text{\reflectbox{$\coloneqq$}}} \cN D \subseteq \N^\N \mathbin{\text{\reflectbox{$\coloneqq$}}} \cN
\] \]
and a continuous bijection from and a continuous bijection $f\colon D \to X$
$D$ onto $X$ (the inverse does not need to be continuous). (the inverse does not need to be continuous).
Moreover there is a continuous surjection $g: \cN \to X$ Moreover there is a continuous surjection $g: \cN \to X$
extending $f$. extending $f$.

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@ -64,7 +64,7 @@
Take $S \coloneqq \{s \in \N^{<\N}: \exists x \in D, n \in \N.~x\defon{n} = s\}$. Take $S \coloneqq \{s \in \N^{<\N}: \exists x \in D, n \in \N.~x\defon{n} = s\}$.
Clearly $S$ is a pruned tree. Clearly $S$ is a pruned tree.
Moreover, since $D$ is closed, we have that (cf.~\yaref{s3e1}) Moreover, since $D$ is closed, we have that\footnote{cf.~\yaref{s3e1}}
\[ \[
D = [S] = \{x \in \N^\N : \forall n \in \N.~x\defon{n} \in S\}. D = [S] = \{x \in \N^\N : \forall n \in \N.~x\defon{n} \in S\}.
\] \]

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@ -1,5 +1,4 @@
\subsection{The Ellis semigroup} \subsection{The Ellis semigroup}
% TODO ANKI-MARKER
\lecture{17}{2023-12-12}{The Ellis semigroup} \lecture{17}{2023-12-12}{The Ellis semigroup}
Let $(X, d)$ be a compact metric space Let $(X, d)$ be a compact metric space
@ -75,7 +74,7 @@ Properties of $(X,T)$ translate to properties of $E(X,T)$:
\] \]
\end{claim} \end{claim}
\begin{subproof} \begin{subproof}
\todo{Homework} Cf.~\yaref{s11e1}
\end{subproof} \end{subproof}
Let $g \in G$. Let $g \in G$.
@ -163,6 +162,8 @@ But it is interesting for other semigroups.
\todo{The other direction is left as an easy exercise.} \todo{The other direction is left as an easy exercise.}
\end{proof} \end{proof}
% TODO ANKI-MARKER
Let $(X,T)$ be a flow. Let $(X,T)$ be a flow.
Then by Zorn's lemma, there exists $X_0 \subseteq X$ Then by Zorn's lemma, there exists $X_0 \subseteq X$
such that $(X_0, T)$ is minimal. such that $(X_0, T)$ is minimal.