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authorFranciszek Malinka <franciszek.malinka@gmail.com>2022-08-24 23:22:12 +0200
committerFranciszek Malinka <franciszek.malinka@gmail.com>2022-08-24 23:22:12 +0200
commit37bb95dea0ac896d9c409fe64f3c1ce99ca43bb2 (patch)
treea6ff9e51b50fe9d6c47edddd4539846833788f76 /sections/conj_classes.tex
parenta15a0040023eb4f8f2b9d9653789063b86ccbe62 (diff)
Fixes
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-rw-r--r--sections/conj_classes.tex14
1 files changed, 9 insertions, 5 deletions
diff --git a/sections/conj_classes.tex b/sections/conj_classes.tex
index 87fa416..e795217 100644
--- a/sections/conj_classes.tex
+++ b/sections/conj_classes.tex
@@ -85,9 +85,10 @@
Let $\cC$ be a Fraïssé class of finitely generated $L$-structures.
Let $\cD$ be the class of structures from $\cC$ with additional unary
function symbol interpreted
- as an automorphism of the structure. If $\cC$ has the weak Hrushovski property
- and $\cD$ is a Fraïssé class, then there is a comeagre conjugacy class in the
- automorphism group of the $\Flim(\cC)$.
+ as an automorphism of the structure. If $\cC$ has the weak Hrushovski
+ property, $\cD$ is a Fraïssé class and $(\Pi, \sigma) = \Flim(\cD)$, then
+ $\Aut(\cC)$ has a comeagre conjugacy class and $\sigma$ is in this class
+ (i.e. $\sigma$ is a generic automorphism).
\end{theorem}
Before we get to the proof, it is important to mention that an isomorphism
@@ -97,7 +98,7 @@
of finitely generated structures (if it yields one) and \textit{vice versa}.
\begin{proof}
- Let $\Gamma = \Flim(\cC)$ and $(\Pi, \sigma) = \Flim(\cD)$. First, by the Theorem
+ Let $\Gamma = \Flim(\cC)$. First, by the Theorem
\ref{theorem:isomorphic_fr_lims}, we may assume without the loss of generality
that $\Pi = \Gamma$. Let $G = \Aut(\Gamma)$,
i.e. $G$ is the automorphism group of $\Gamma$.
@@ -228,7 +229,10 @@
\begin{theorem}
\label{theorem:key-theorem}
Let $\cC$ be a Fraïssé class of finitely generated $L$-structures with WHP
- and canonical amalgamation. Then $\Flim(\cC)$ has a generic automorphism.
+ and canonical amalgamation. Let $\cD$ be the class of structures from $\cC$ with
+ additional unary function symbol interpreted as an automorphism of the structure.
+ Then $\cD$ is a Fraïssé class and for $(\Pi, \sigma) = \Flim(\cD)$
+ we have that the conjugacy class of $\sigma$ is comeagre in $\Aut(\cC)$.
\end{theorem}
\begin{proof}