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Spencer Killen 2024-11-07 06:47:25 -07:00
parent c4da7b6c43
commit a3f036ff8d
Signed by: sjkillen
GPG Key ID: 3AF3117BA6FBB75B
3 changed files with 70 additions and 10 deletions

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@ -6,8 +6,16 @@
\newcommand{\Image}{\definitionLink{image}{monotone}}
\let\imageNoLink\image
\renewcommand{\image}[1]{\imageNoLink{#1}}
\let\lubNoLink\lub
\renewcommand{\lub}{\definitionLink{lubglb}{\lubNoLink}}
\let\glbNoLink\glb
\renewcommand{\glb}{\definitionLink{lubglb}{\glbNoLink}}
\newcommand{\CompleteLattice}{\definitionLink{completelattice}{complete lattice}}
\let\topNoLink\top
\renewcommand{\top}{\definitionLink{topbot}{\topNoLink}}
\let\botNoLink\bot
\renewcommand{\bot}{\definitionLink{topbot}{\botNoLink}}
\let\fixpointsOfNoLink\fixpointsOf{}
\renewcommand{\fixpointsOf}{\definitionLink{fixpointsOf}{\fixpointsOfNoLink}}

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@ -4,3 +4,5 @@
\newcommand{\image}[1]{[#1]}
\newcommand{\define}{\coloneqq}
\newcommand{\union}{\cup}
\newcommand{\glb}{\bigwedge}
\newcommand{\lub}{\bigvee}

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@ -15,6 +15,9 @@
\pagestyle{plain}
\newtheorem{theorem}{Theorem}
\newtheorem{corollary}{Corollary}
\newtheorem{lemma}{Lemma}
\newtheorem{proposition}{Proposition}
\begin{document}
@ -22,6 +25,8 @@
\definition{monotone}{define monotone}
\definition{image}{define set image}
\definition{lubglb}{define glb and lub}
\definition{topbot}{define $\top$ and $\bot$}
\definition{completelattice}{define complete lattice}
Hello world\cite{tarskilatticetheoretical1955}
@ -30,31 +35,76 @@ First, we generalize Knaster-Tarski Fixpoint Theorem.
$$\fixpointsOf(S)$$
\begin{theorem}[Tarski-Knaster Fixpoint Theorem~\cite{tarskilatticetheoretical1955}]
\begin{theorem}[Tarski-Knaster Fixpoint Theorem~\cite{tarskilatticetheoretical1955}]\label{tarskitheorem}
For a \Monotone function $o$ over a \CompleteLattice $\langle \L, \lte \rangle$, we have that $\langle \fixpointsOf(o), \lte \rangle$ is a \CompleteLattice.
\end{theorem}
\begin{theorem}
Trivial attempt using set preimage / image to attain LUB / GLB in image lattice does not work.
Consider antichain of 2 that map to a chain in image.
The antichain's LUB does maps to a third, distinct element which extends the chain to three in the image
If we attain LUB of preimage, then its not the least element :)
\end{theorem}
\begin{theorem}\label{imagelattice}
For a \Monotone function $o$ over a \CompleteLattice $\langle \L, \lte \rangle$, we have that $\langle o\imageNoLink{\L}, \lte \rangle$ is a \CompleteLattice.
\end{theorem}
\begin{proof}
Consider $\langle \L', \lte' \rangle$ where
Consider $\langle \L', \lte \rangle$ where
\begin{align*}
\L' \define \{ x' ~|~ x \in \L \} \\
x' \lte' y' \iff x \lte y \textrm{ where } x, y \in \L
x' \lte y' \iff x \lte y \textrm{ where } x, y \in \L
\end{align*}
Clearly, $\langle \L', \lte' \rangle$ is a \CompleteLattice.
Combining $\L$ and $\L'$
Combining $\L$ and $\L'$, we formulate $\L^*$:
\begin{align*}
\L^* \define \{ \top^*, \bot^* \} \union \L \union \L' \\
\forall x^*, y^* \in \L^*, x^* \lte y^* \iff \begin{cases}
(x^* = \bot^*) \lor (y^* = \top^*) \\
two \\
three
\L^* &\define \{ \top^*, \bot^* \} \union \L \union \L' \\
\forall x^*, y^* \in \L^*, x^* \lte y^* &\iff \begin{cases}
(x^* = \bot^*) \lor (y^* = \top^*), \\
\textrm{or } x, y \in \L, \\
\textrm{or } x', y' \in \L'
\end{cases}
\end{align*}
It is easy to show that $\langle \L^*, \lte \rangle$ is a \CompleteLattice.
Consider the operator $o^*$ that maps elements from $\L$ to $\L'$ and every element in $\L'$ to itself.
\begin{align*}
o^*(x) \define \begin{cases}
o(x)' & \textrm{if } x \in \L \\
x & \textrm{otherwise}
\end{cases}
\end{align*}
We have $o^*\image{\L \union \L'} \subseteq L'$ and $\fixpointsOf(o^*) = o\image{\L}' \union \{ \bot^*, \top^* \}$.
By Tarski-Knaster Fixpoint Theorem (Theorem \ref{tarskitheorem}), $\fixpointsOf(o^*)$ is a \CompleteLattice.
Thus, $o\image{\L} \union \{ \bot^*, \top^* \}$ is a \CompleteLattice. For any $S \subseteq \L$, we have $\glb S \not\in \{ \bot^*, \top^* \}$ and $\lub S \not\in \{ \bot^*, \top^* \}$, thus $\langle o\image{\L}, \preceq \rangle$ is a \CompleteLattice.
\end{proof}
The following follows directly from the contrapositive of Theorem \ref{imagelattice}.
\begin{corollary}
If $\langle o\image{\L}, \lte \rangle$ is not a \CompleteLattice, then $o$ is not \Monotone.
\end{corollary}
\begin{definition}
An approximator set $H$ captures a nondeterministic approximator $o$ if for each consistent pair $(x, y)$
\begin{align*}
(H\image{(x, y)}_1, H\image{(x, y)}_2) = o(x, y)
\end{align*}
\end{definition}
\begin{theorem}
A nondeterministic approximator $o$ has a set of
\end{theorem}
\begin{theorem}
For any nondeterministic approximator $o$, there exists an approximator set $H$ s.t.\ gamma stable models correspond to n-stable models
\end{theorem}
\begin{proof}
foo
\end{proof}
\bibliographystyle{plain}
\bibliography{references}