diff --git a/draft/draft.tex b/draft/draft.tex index 70dad02..46a08d4 100644 --- a/draft/draft.tex +++ b/draft/draft.tex @@ -1940,36 +1940,36 @@ To define $\delta$, we define $c\c(\mathcal{P}R^\dagger)\to((\mathcal{P}R^\dagge \end{definition} \begin{definition}[Hermida-Jacobs Simulation] - For a relator $\relar$ on a functor $F$, and a poset $\appr$ over $F$ a HJ-simulation is a relation $r$ for which there exists a morphism $\sigma\c r\to\relar r$ called \emph{witness} such that the following diagram commutes ($;$ is the relation composition): + For a relator $\relar$ on a functor $F$ a HJ-simulation is a relation $r$ for which there exists a morphism $\sigma\c r\to\relar r$ called \emph{witness} such that the following diagram commutes ($;$ is the relation composition): \begin{equation*}\label{def:hej-sim} \begin{tikzcd}[ampersand replacement=\&] X \& r \& Y \\ - {FX} \& {\appr;\relar r;\appr} \& {FY} + {FX} \& {\relar r} \& {FY} \arrow["\alpha"', from=1-1, to=2-1] \arrow["{p_1}"', from=1-2, to=1-1] \arrow["{p_2}", from=1-2, to=1-3] \arrow["\sigma", from=1-2, to=2-2] \arrow["\beta", from=1-3, to=2-3] - \arrow["{{Fp_1}_\appr}", from=2-2, to=2-1] - \arrow["{{Fp_2}_\appr}"', from=2-2, to=2-3] + \arrow["{{(Fp_1)}^\relar}", from=2-2, to=2-1] + \arrow["{{(Fp_2)}^\relar}"', from=2-2, to=2-3] \end{tikzcd} \end{equation*} \end{definition} -\begin{prop} - Hughes-Jacobs simulation is an instance of HJ-simulation, where $\relar r=(Fr)^\dagger$. -\end{prop} -\begin{proof} - We need to show that $(F-)^\dagger$ is a relator. We need to show that for a relations $r_1$ and $r_2$, where $r_1\appr r_2$ we have $\relar r_1\appr \relar r_2$. (What is $\appr$?!) - - \todo{Sergey claims this. Ask him how can he?} -\end{proof} \begin{prop} For an arbitrary relator $\relar$ on a functor $F$, if a relation $r$ is a HJ-simulation, the witness is unique. \end{prop} \begin{proof} - It only relies on the fact that ${Fp_1}_\appr$ and ${Fp_2}_\appr$ in~\eqref{def:hej-sim} are jointly monic.\qed + It only relies on the fact that ${(Fp_1)}^\relar_\appr$ and ${(Fp_2)}^\relar_\appr$ in~\eqref{def:hej-sim} are jointly monic.\qed \end{proof} - +\begin{definition} + We call $\hat{\relar}$ a symmetrization of a relator $\relar$ iff for a relation $r$ it is defined as follows: + \begin{gather*} + \hat{\relar}r=\relar r\cap (\relar(r^\op))^\op + \end{gather*} +\end{definition} +\begin{prop} + Assuming that $\relar$ is a relator, and $r$ is a symmetric relation that is a simulation for $\relar$, then $r$ is also a simulation for $\hat{\relar}$. +\end{prop} \end{document}