Symmetric relations

http://mathcs.chapman.edu/structuresold/files/Symmetric_relations.pdf

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\begin{document}
\textbf{\Large Symmetric relations}
\quad\href{http://math.chapman.edu/cgi-bin/structures?action=edit;id=Symmetric_relations}{edit}

\abbreviation{SymRel}

\begin{definition}
A \emph{symmetric relation} is a structure $\mathbf{X}=\langle X,R\rangle$ such that $R$ is a \emph{binary relation on $X$} 
(i.e. $R\subseteq X\times X$) that
is

symmetric:  $xRy\implies yRx$

Remark: This is a template.
If you know something about this class, click on the ``Edit text of this page'' link at the bottom and fill out this page.

It is not unusual to give several (equivalent) definitions. Ideally, one of the definitions would give an irredundant axiomatization that does not refer to other classes.
\end{definition}

\begin{morphisms}
Let $\mathbf{X}$ and $\mathbf{Y}$ be symmetric relations. A morphism from $\mathbf{X}$ to $\mathbf{Y}$ is a function $h:A\rightarrow B$ that is a homomorphism: 
$xR^{\mathbf X} y\implies h(x)R^{\mathbf Y}h(y)$
\end{morphisms}

\begin{definition}
\end{definition}

\begin{basic_results}
\end{basic_results}

\begin{examples}
\begin{example}
\end{example}
\end{examples}

\begin{table}[h]
\begin{properties} (\href{http://math.chapman.edu/cgi-bin/structures?Properties}{description})

Feel free to add or delete properties from this list. The list below may contain properties that are not relevant to the class that is being described.

\begin{tabular}{|ll|}\hline
  Classtype                       & quasivariety \\\hline
  Quasiequational theory          & \\\hline
  First-order theory              & \\\hline
  Locally finite                  & yes\\\hline
  Residual size                   & \\\hline
  Congruence distributive         & no\\\hline
  Congruence modular              & no\\\hline
  Congruence $n$-permutable       & \\\hline
  Congruence regular              & \\\hline
  Congruence uniform              & \\\hline
  Congruence extension property   & \\\hline
  Definable principal congruences & \\\hline
  Equationally def. pr. cong.     & \\\hline
  Amalgamation property           & \\\hline
  Strong amalgamation property    & \\\hline
  Epimorphisms are surjective     & \\\hline
\end{tabular}
\end{properties}
\end{table}

\begin{finite_members} $f(n)=$ number of members of size $n$.

$\begin{array}{lr}
  f(1)= &1\\
  f(2)= &\\
  f(3)= &\\
  f(4)= &\\
  f(5)= &\\
\end{array}$\qquad
$\begin{array}{lr}
  f(6)= &\\
  f(7)= &\\
  f(8)= &\\
  f(9)= &\\
  f(10)= &\\
\end{array}$

\end{finite_members}

\begin{subclasses}\ 

\end{subclasses}

\begin{superclasses}\ 

  \href{Directed_graphs.pdf}{Directed graphs} supervariety

\end{superclasses}

\begin{thebibliography}{10}

\bibitem{Lastname19xx}
F. Lastname, \emph{Title}, Journal, \textbf{1}, 23--45 \href{http://www.ams.org/mathscinet-getitem?mr=12a:08034}{MRreview} 

\end{thebibliography}

\end{document}
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