diff --git a/draft/draft.tex b/draft/draft.tex index 1c9decb..591bd2a 100644 --- a/draft/draft.tex +++ b/draft/draft.tex @@ -2162,9 +2162,32 @@ Egli-Milner relator is not sound or complete, although its symmetrization is sou $\hat{\emre}$-similarity from a coalgebra $(\alpha,X)$ to $(\beta,Y)$ is sound and complete. \end{prop} \begin{proof} - \todo{Finish.} + We need to prove that for every functions $f\c X\to Z$ and $g\c Y\to Z$, $\hat{\emre}(g^\op\comp f)=(\powf g)^\op\comp\powf f$. + We have $S\;\hat{\emre}(g^\op\comp f)\;T$ iff $S\;\emre(g^\op\comp f)\;T$ and $T\;\emre(f^\op\comp g)\;S$. Then we have + \begin{align*} + S\;\emre(g^\op\comp f)\;T&\\ + &\iff\forall x\in S,\exists y\in T, x\;g^\op\comp f\; y\\ + &\iff \forall x\in S,\exists y\in T,z\in Z, x\;f\;z\; , \; y\;g\;z, + \end{align*} + and + \begin{align*} + T\;\emre(f^\op\comp g)\;S&\\ + &\iff\forall y\in T,\exists x\in S, y\;f^\op\comp g\; x\\ + &\iff \forall y\in T,\exists x\in S, z\in Z, x\;f\;z\; , \; y\;g\;z. + \end{align*} + It is equivalent with the following: + \begin{gather*} + \forall x\in S,\exists y\in T, f(x)=g(y),\\ + \forall y\in T,\exists x\in S, f(x)=g(y). + \end{gather*} + Equivalently, $Im(f)=Im(g)$, and we call images $U$ that is in $\powf Z$. So, we equivalently have + \begin{align*} + S\;\powf f\;U,\; T\;\powf g\;U&\\ + &\iff S\;\powf f\;U,\; U\;(\powf g)^\op\;T\\ + &\iff S\;(\powf g)^\op\comp\powf f\;T + \end{align*}\qed \end{proof} -The symmetrization of the Egli-Milner relator is a Barr-relator. Barr-relators is a generalization of the Egli-Milner relator, where the functor is generalized. +The symmetrization of the Egli-Milner relator is a Barr-relator. Barr-relator is a generalization of the Egli-Milner relator, where the functor is generalized. \begin{prop} Assuming that $r\c X\rto Y$, and $\appr_{X}$ and $\appr_{Y}$ are posets over $FX$ and $FY$ respectively, then $\appr_{X};\hat{\emre};\appr_{Y}=\appr_{X};\hat{\emre}$ and $\appr_{X};\hat{\emre}=\hat{\emre};\appr_{Y}$.