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authorFranciszek Malinka <franciszek.malinka@gmail.com>2022-07-09 13:44:59 +0200
committerFranciszek Malinka <franciszek.malinka@gmail.com>2022-07-09 13:44:59 +0200
commite55ffead297fd04fe73e5f7bd6d05a151450fb99 (patch)
tree4a173d26144a7b78ae1fd94ff8f2617d20f9efd9
parentbd01da032991f9671557ef64e23ca684fa6c995a (diff)
Aspelled
-rw-r--r--lic_malinka.tex2
-rw-r--r--sections/conj_classes.tex5
-rw-r--r--sections/fraisse_classes.tex9
-rw-r--r--sections/preliminaries.tex45
4 files changed, 41 insertions, 20 deletions
diff --git a/lic_malinka.tex b/lic_malinka.tex
index a469805..bf8fad5 100644
--- a/lic_malinka.tex
+++ b/lic_malinka.tex
@@ -89,10 +89,8 @@
\newtheorem*{question2}{Question}
\newtheorem*{conjecture2}{Conjecture}
-
\newtheorem{clm}{Claim} \newtheorem*{clm*}{Claim}
-
\theoremstyle{definition}
\newtheorem{definition}[theorem]{Definition}
\newtheorem*{definition2}{Definition}
diff --git a/sections/conj_classes.tex b/sections/conj_classes.tex
index 8beace0..3e4cb3a 100644
--- a/sections/conj_classes.tex
+++ b/sections/conj_classes.tex
@@ -91,7 +91,7 @@
that $\Pi = \Gamma$.
We will construct a strategy for the second player in the Banach-Mazur game
on the topological space $G$. This strategy will give us a subset
- $A\subseteq G$ and as we will see a subset of a cojugacy class in $G$.
+ $A\subseteq G$ and as we will see a subset of a conjugacy class in $G$.
By the Banach-Mazur theorem \ref{theorem:banach_mazur_thm} this will prove
that this class is comeagre.
@@ -234,6 +234,7 @@
% infinite and has the random graph property.
% \end{proof}
\begin{proposition}
+ \label{proposition:fixed_points}
Let $\sigma$ be the generic automorphism of $\Gamma$. Then the set
of fixed points of $\sigma$ is isomorphic to $\Gamma$.
\end{proposition}
@@ -242,7 +243,7 @@
Let $S = \{x\in \Gamma\mid \sigma(x) = x\}$.
First we need to show that it is an infinite. By the theorem \ref{theorem:generic_aut_general}
we know that $(\Gamma, \sigma)$ is the Fraïssé limit of $\cH$, thus we
- can embedd finite $L$-structures of any size with identity as an
+ can embed finite $L$-structures of any size with identity as an
automorphism of the structure into $(\Gamma, \sigma)$. Thus $S$ has to be
infinite. Also, the same argument shows that the age of the structure is
exactly $\cC$. It is weakly ultrahomogeneous, also by the fact that
diff --git a/sections/fraisse_classes.tex b/sections/fraisse_classes.tex
index 9110f44..dc6392d 100644
--- a/sections/fraisse_classes.tex
+++ b/sections/fraisse_classes.tex
@@ -149,6 +149,7 @@
\end{proof}
\begin{definition}
+ \label{definition:random_graph}
The \emph{random graph} is the Fraïssé limit of the class of finite graphs
$\cG$ denoted by $\FrGr = \Flim(\cG)$.
\end{definition}
@@ -253,7 +254,7 @@
\end{tikzcd}
\end{center}
- We have deliberately omited names for embeddings of $C$. Of course,
+ We have deliberately omitted names for embeddings of $C$. Of course,
the functor has to take them into account, but this abuse of notation
is convenient and should not lead into confusion.
\item Let $A\leftarrow C\rightarrow B$, $A'\leftarrow C\rightarrow B'$ be cospans
@@ -414,13 +415,13 @@
theorem \ref{theorem:fraisse_thm} it suffices to show that the age of $\Pi$
is $\cC$ and that it has the weak ultrahomogeneity in the class $\cC$. The
former comes easily, as for every structure $A\in \cC$ we have the structure
- $(A, \id_A)\in \cD$, which means that the structure $A$ embedds into $\Pi$.
- Also, if a structure $(B, \beta)\in\cD$ embedds into $\cD$, then $B\in\cC$.
+ $(A, \id_A)\in \cD$, which means that the structure $A$ embeds into $\Pi$.
+ Also, if a structure $(B, \beta)\in\cD$ embeds into $\cD$, then $B\in\cC$.
Hence, $\cC$ is indeed the age of $\Pi$.
Now, take any structure $A, B\in\cC$ such that $A\subseteq B$. Without the
loss of generality assume that $A = B\cap \Pi$. Let $\bar{A}$ be the
- smallest structure closed on the automorphism $\sigma$ and containg $A$.
+ smallest structure closed on the automorphism $\sigma$ and containing $A$.
It is finite, as $\cC$ is the age of $\Pi$. By the weak Hrushovski property,
of $\cC$ let $(\bar{B}, \beta)$ be a structure extending
$(B\cup \bar{A}, \sigma\upharpoonright_{\bar{A}})$. Again, we may assume
diff --git a/sections/preliminaries.tex b/sections/preliminaries.tex
index 832beae..5f53c0a 100644
--- a/sections/preliminaries.tex
+++ b/sections/preliminaries.tex
@@ -1,7 +1,27 @@
\documentclass[../lic_malinka.tex]{subfiles}
\begin{document}
+ Before we get to the main work of the paper, we need to establish basic
+ notions, known facts and theorems. This section provides a brief
+ introduction to the theory of Baire spaces and category theory.
+ Most of the notions are well known, interested reader may look at
+ \cite{descriptive_set_theory}, \cite{maclane_1978}
+
\subsection{Descriptive set theory}
+ In this section we provide an important definition of a \emph{comeagre} set.
+ It is purely topological notion, the intuition may come from the measure
+ theory though. For example, in a standard Lebesuge measure on the
+ real interval $[0,1]$, the set of rationals is of measure $0$, although
+ being a dense subset of the $[0,1]$. So, in a sense, the set of rationals
+ is \emph{meagre} in the interval $[0,1]$. On the other hand, the set
+ of irrational numbers is also dense, but have measure $1$, so it is
+ \emph{comeagre}.
+
+ This is only a rough approximation of the topological
+ definition. The definitions are based on the Kechris' book \textit{Classical
+ Descriptive Set Theory} \cite{descriptive_set_theory}. One should look into
+ it for more details and examples.
+
\begin{definition}
Suppose $X$ is a topological space and $A\subseteq X$.
We say that $A$ is \emph{meagre} in $X$ if $A = \bigcup_{n\in\bN}A_n$,
@@ -15,11 +35,10 @@
contains a countable intersection of open dense sets.
\end{definition}
- % \begin{example}
- Every countable set is meagre in any $T_1$ space, so, for example, $\bQ$
+ Every countable set is meagre in any $T_1$ space. So, $\bQ$
is meagre in $\bR$ (although it is dense), which means that the set of
- irrationals is comeagre. Another example is...
- % \end{example}
+ irrationals is comeagre. The Cantor set is nowhere dense, hence meagre
+ in the $[0,1]$ interval.
\begin{definition}
We say that a topological space $X$ is a \emph{Baire space} if every
@@ -43,10 +62,10 @@
$\bigcap_{n}V_n \subseteq A$.
\end{definition}
- There is an important theorem on the Banach-Mazur game: $A$ is comeagre
- if and only if $\textit{II}$ can always choose sets $V_0, V_1, \ldots$ such that
- it wins. Before we prove it we need to define notions necessary to
- formalise and prove the theorem.
+ There is an important theorem \ref{theorem:banach_mazur_thm} on the
+ Banach-Mazur game: $A$ is comeagre if and only if $\textit{II}$ can always
+ choose sets $V_0, V_1, \ldots$ such that it wins. Before we prove it we need
+ to define notions necessary to formalise and prove the theorem.
\begin{definition}
$T$ is \emph{the tree of all legal positions} in the Banach-Mazur game
@@ -96,16 +115,18 @@
$\bigcap_{n}V_n \subseteq A$.
\end{definition}
- Now we can state the key theorem.
-
\begin{theorem}[Banach-Mazur, Oxtoby]
\label{theorem:banach_mazur_thm}
Let $X$ be a nonempty topological space and let $A\subseteq X$. Then A is
comeagre $\Leftrightarrow$ $\textit{II}$ has a winning strategy in
$G^{\star\star}(A)$.
\end{theorem}
+
+ The statement of the theorem is once again taken from Kechris
+ \cite{descriptive_set_theory} 8.33. However, the proof given in the book is
+ brief, thus we present a detailed version. In order to prove the
+ theorem we add an auxiliary definition and lemma.
- In order to prove it we add an auxiliary definition and lemma.
\begin{definition}
Let $S\subseteq\sigma$ be a pruned subtree of tree of all legal positions
$T$ and let $p=(U_0, V_0,\ldots, V_n)\in S$. We say that S is
@@ -336,7 +357,7 @@
\end{definition}
\begin{definition}
- The \emph{cospan category} of category $\cC$, refered to as $\Cospan(\cC)$,
+ The \emph{cospan category} of category $\cC$, referred to as $\Cospan(\cC)$,
is the category of cospan diagrams of $\cC$, where morphisms between
two cospans are normal transformations of the underlying functors.