diff --git a/inputs/lecture_11.tex b/inputs/lecture_11.tex index ebdd95f..53d2c7e 100644 --- a/inputs/lecture_11.tex +++ b/inputs/lecture_11.tex @@ -173,10 +173,8 @@ i.e.~we want to associate a tree $T \subseteq \N^{<\N}$}% Let \vocab{$\Tr$} $ \coloneqq \{T \in {2^{\N}}^{<\N} : T \text{ is a tree}\} \subseteq {2^{\N}}^{<\N}$. \begin{observe} - \[ - \Tr \subseteq {2^{\N}}^{<\N} - \] - is closed (where we take the topology of the Cantor space). + $\Tr \subseteq {2^{\N}}^{<\N}$ is closed + (where we take the topology of the Cantor space). \end{observe} \gist{% Indeed, for any $ s \in \N^{<\N}$ diff --git a/inputs/lecture_13.tex b/inputs/lecture_13.tex index 5d9cd9c..f68c640 100644 --- a/inputs/lecture_13.tex +++ b/inputs/lecture_13.tex @@ -33,7 +33,6 @@ with $(f^{-1}(\{1\}), <)$. and $[\alpha_i, \alpha_{i+1})$ to $(i,i+1)$. \end{proof} -% TODO ANKI-MARKER \begin{definition}[\vocab{Kleene-Brouwer ordering}] Let $(A,<)$ be a linear order and $A$ countable. @@ -58,25 +57,30 @@ with $(f^{-1}(\{1\}), <)$. $(T, <_{KB}\defon{T})$ is well ordered. \end{proposition} \begin{proof} - If $T$ is ill-founded and $x \in [T]$, - then for all $n$, we have $x\defon{n+1} <_{KB} x\defon{n}$. - Thus $(T, <_{KB}\defon{T})$ is not well ordered. + \gist{% + If $T$ is ill-founded and $x \in [T]$, + then for all $n$, we have $x\defon{n+1} <_{KB} x\defon{n}$. + Thus $(T, <_{KB}\defon{T})$ is not well ordered. - Conversely, let $<\defon{KB}$ be not a well-ordering - on $T$. - Let $s_0 >_{KB} s_1 >_{KB} s_2 >_{KB} \ldots$ - be an infinite descending chain. - We have that $s_0(0) \ge s_1(0) \ge s_2(0) \ge \ldots$ - stabilizes for $n > n_0$. - Let $a_0 \coloneqq s_{n_0}(0)$. - Now for $n \ge n_0$ we have that $s_n(0)$ is constant, - hence for $n > n_0$ the value $s_{n}(1)$ must be defined. - Thus there is $n_1 \ge n_0$ such that $s_n(1)$ - is constant for all $n \ge n_1$. - Let $a_1 \coloneqq s_{n_1}(1)$ - and so on. - Then $(a_0,a_1,a_2, \ldots) \in [T]$. + Conversely, let $<\defon{KB}$ be not a well-ordering + on $T$. + Let $s_0 >_{KB} s_1 >_{KB} s_2 >_{KB} \ldots$ + be an infinite descending chain. + We have that $s_0(0) \ge s_1(0) \ge s_2(0) \ge \ldots$ + stabilizes for $n > n_0$. + Let $a_0 \coloneqq s_{n_0}(0)$. + Now for $n \ge n_0$ we have that $s_n(0)$ is constant, + hence for $n > n_0$ the value $s_{n}(1)$ must be defined. + Thus there is $n_1 \ge n_0$ such that $s_n(1)$ + is constant for all $n \ge n_1$. + Let $a_1 \coloneqq s_{n_1}(1)$ + and so on. + Then $(a_0,a_1,a_2, \ldots) \in [T]$. + }{easy} \end{proof} + +% TODO ANKI-MARKER + \begin{theorem}[Lusin-Sierpinski] The set $\LO \setminus \WO$ (resp.~$2^{\Q} \setminus \WO$) diff --git a/jrpie-gist.sty b/jrpie-gist.sty index ea7caa3..405fecf 100644 --- a/jrpie-gist.sty +++ b/jrpie-gist.sty @@ -4,6 +4,7 @@ % TODO gist info % TODO link to long version (provide link to main document) +% TODO \phantomsection to cross link \newcommand{\gist}[2]{% \ifcsname EnableGist\endcsname% #2%