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3 changed files with 6 additions and 5 deletions
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@ -199,8 +199,8 @@
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\[
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\[
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D \subseteq \N^\N \mathbin{\text{\reflectbox{$\coloneqq$}}} \cN
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D \subseteq \N^\N \mathbin{\text{\reflectbox{$\coloneqq$}}} \cN
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\]
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\]
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and a continuous bijection from
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and a continuous bijection $f\colon D \to X$
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$D$ onto $X$ (the inverse does not need to be continuous).
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(the inverse does not need to be continuous).
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Moreover there is a continuous surjection $g: \cN \to X$
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Moreover there is a continuous surjection $g: \cN \to X$
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extending $f$.
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extending $f$.
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@ -64,7 +64,7 @@
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Take $S \coloneqq \{s \in \N^{<\N}: \exists x \in D, n \in \N.~x\defon{n} = s\}$.
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Take $S \coloneqq \{s \in \N^{<\N}: \exists x \in D, n \in \N.~x\defon{n} = s\}$.
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Clearly $S$ is a pruned tree.
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Clearly $S$ is a pruned tree.
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Moreover, since $D$ is closed, we have that (cf.~\yaref{s3e1})
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Moreover, since $D$ is closed, we have that\footnote{cf.~\yaref{s3e1}}
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\[
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\[
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D = [S] = \{x \in \N^\N : \forall n \in \N.~x\defon{n} \in S\}.
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D = [S] = \{x \in \N^\N : \forall n \in \N.~x\defon{n} \in S\}.
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\]
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\]
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@ -1,5 +1,4 @@
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\subsection{The Ellis semigroup}
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\subsection{The Ellis semigroup}
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% TODO ANKI-MARKER
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\lecture{17}{2023-12-12}{The Ellis semigroup}
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\lecture{17}{2023-12-12}{The Ellis semigroup}
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Let $(X, d)$ be a compact metric space
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Let $(X, d)$ be a compact metric space
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@ -75,7 +74,7 @@ Properties of $(X,T)$ translate to properties of $E(X,T)$:
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\]
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\]
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\end{claim}
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\end{claim}
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\begin{subproof}
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\begin{subproof}
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\todo{Homework}
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Cf.~\yaref{s11e1}
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\end{subproof}
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\end{subproof}
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Let $g \in G$.
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Let $g \in G$.
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@ -163,6 +162,8 @@ But it is interesting for other semigroups.
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\todo{The other direction is left as an easy exercise.}
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\todo{The other direction is left as an easy exercise.}
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\end{proof}
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\end{proof}
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% TODO ANKI-MARKER
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Let $(X,T)$ be a flow.
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Let $(X,T)$ be a flow.
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Then by Zorn's lemma, there exists $X_0 \subseteq X$
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Then by Zorn's lemma, there exists $X_0 \subseteq X$
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such that $(X_0, T)$ is minimal.
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such that $(X_0, T)$ is minimal.
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