Changeset - c2fa910c4916
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Tom Bannink - 8 years ago 2017-07-06 17:33:23
tom.bannink@cwi.nl
Add circle version of lemma
3 files changed with 115 insertions and 49 deletions:
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diagram_circle_lemma.pdf
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diagram_circle_lemma.tex
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@@ -37,13 +37,13 @@
 
    }
 

	
 
    % Legend
 
    \draw (-1,0)+(-0.5,-1) rectangle +(2.2,1);
 
    \draw (-1,0)+(-0.5,-1) rectangle +(2.6,1);
 
    \draw[fill,red]   (-1.1,0.5)  circle (0.09);
 
    \draw[fill,blue]  (-1.1,0)    +(-0.1,-0.1) rectangle +(0.1,0.1);
 
    \draw[fill,green] (-1.1,-0.5) +(-0.15,-0.1) -- +(0.15,-0.1) -- +(0,0.15);
 
    \draw[anchor=west] (-1,0.5)  node {$I$};
 
    \draw[anchor=west] (-1,0)    node {$I_{\mathrm{in}(n-l,k)}$};
 
    \draw[anchor=west] (-1,-0.5) node {$I_{\mathrm{out}(n-l,k)}$};
 
    \draw[anchor=west] (-1,0)    node {$I\cap [{\color{gray}n}{-l},r]_0$};
 
    \draw[anchor=west] (-1,-0.5) node {$I\setminus[{\color{gray}n}{-l},r]_0$};
 

	
 

	
 
    % Bigger circle
 
@@ -51,8 +51,8 @@
 
        \draw[-,dashed] ({\a*\step}:\r+1) -- ({(\a+1)*\step}:\r+1);
 
        %\draw ({\a*\step}:\r+1) circle (0.05);
 
    }
 
    \draw ({-5*\step}:\r+1) +(0.2,-0.2) node {$n-l$};
 
    \draw ({4*\step}:\r+1) +(0.2,0.2) node {$k$};
 
    \draw ({-5*\step}:\r+1) +(0.2,-0.2) node {${\color{gray}n}{-l}$};
 
    \draw ({4*\step}:\r+1) +(0.2,0.2) node {$r$};
 

	
 

	
 
    %
 
@@ -65,10 +65,13 @@
 
    \draw ({1*\step}:\r-0.3) node {$1$};
 
    % n/2
 
    \draw ({12*\step}:\r-0.3) node {$\frac{n}{2}$};
 
    % n-1
 
    \draw ({-1*\step}:\r-0.3) +(-0.4,0) node {${\color{gray}n}{-1}$};
 
    % i_*
 
    \draw[->] ({10*\step}:\r-1) -- ({10*\step}:\r-0.2);
 
    \draw ({10*\step}:\r-1) +(0.3,0) node {$i_*$};
 
    % n-1
 
    \draw ({-1*\step}:\r-0.3) +(-0.4,0) node {$n-1$};
 
    % j
 
    \draw[->] ({0*\step}:\r-1.3) -- ({0*\step}:\r-0.8);
 
    \draw ({0*\step}:\r-1) +(-0.4,0) node {$j$};
 
\end{tikzpicture}
 
\end{document}
main.tex
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@@ -59,6 +59,13 @@
 
\newcommand{\paths}[1]{\mathcal{P}\left(#1\to\mathbf{1}\right)}
 
\newcommand{\maxgap}[1]{\mathrm{maxgap}\left(#1\right)}
 
\newcommand{\gaps}[1]{#1_{\mathrm{gaps}}}
 
\renewcommand{\P}{\mathbb{P}}
 
\newcommand{\NZ}[1]{\mathrm{NZ}^{(#1)}}
 
\newcommand{\Z}[1]{\mathrm{Z}^{(#1)}}
 
%\newcommand{\dist}[1]{d_{\!\!\not\,#1}}
 
\newcommand{\dist}[1]{d_{\neg #1}}
 

	
 
\newcommand{\todo}[1]{{\color{red}\textbf{TODO:} #1}}
 

	
 
\long\def\ignore#1{}
 

	
 
@@ -418,12 +425,12 @@ where we used the identity $\sum_{a\in\{0,1\}^l} (-1)^{|a|} = 0$.
 

	
 
\newpage
 
\subsection{Proving the strong cancellation claim}
 
It is useful to introduce some new notation:
 
It is useful to introduce some new notation. Note that an \emph{event} is a subset of all possible paths of the Markov Chain.
 
\begin{definition}[Events conditioned on starting state] \label{def:conditionedevents}
 
    For any state $b\in\{0,1\}^n$ and any event $A$ (where an event is a subset of all possible paths of the Markov Chain), define
 
    For any state $b\in\{0,1\}^n$, define $\textsc{start}(b)$ as the event that the starting state of the chain is the state $b$. For any event $A$, define
 
    \begin{align*}
 
        \mathbb{P}_b(A) &= \mathbb{P}(A \;|\; \text{start in }b) \\
 
        R_{b,A} &= \mathbb{E}( \#resamples \;|\; A \; \& \; \text{start in }b)
 
        \mathbb{P}_b(A) &= \mathbb{P}(A \;|\; \textsc{start}(b)) \\
 
        R_{b,A} &= \mathbb{E}( \#resamples \;|\; A \; , \; \textsc{start}(b))
 
    \end{align*}
 
\end{definition}
 
\begin{definition}[Vertex visiting event] \label{def:visitingResamplings}
 
@@ -471,7 +478,7 @@ The lemma says that conditioned on $j_1$ and $j_2$ not being crossed, the two ha
 
        \; \cdot \;
 
        \mathbb{P}_{b_2}(\mathrm{NZ}^{(j_1,j_2)},A_2).
 
    \end{align*}
 
    The second equality follows directly from Bayes rule and removing $A_1,A_2$.
 
    The second equality follows directly from $\mathbb{P}(A\mid B)=\mathbb{P}(A,B)/\mathbb{P}(B)$ and setting $A_1,A_2$ to the always-true event.
 
    For the third equality, note that again by the same reasoning as in the proof of claim \ref{claim:expectationsum} we have
 
    \begin{align*}
 
        \mathbb{P}_b(\mathrm{NZ}^{(j_1,j_2)},A_1,A_2) R_{b,\mathrm{NZ}^{(j_1,j_2)},A_1,A_2}
 
@@ -588,46 +595,102 @@ The intuition of the following lemma is that the far right can only affect the z
 

	
 
~
 

	
 
Here, I (Tom) tried to set up the same Lemma but for the circle instead of the infinite chain.
 
This time, it is no longer $I_\mathrm{max}$ but any vertex $i_* \in I$, and $I' = I \setminus \{i_*\}$. Without loss of generality, we can assume that $i_* \leq n/2$ so that the distance to $0$ is simply $d(i_*,0)=i_*$ (because if not then we can relabel the vertices and count the other way around so that $i_* \to n-i_*$). The goal is now to prove:
 
\begin{align*}
 
    P_I(Z^{(0)}) = P_{I'}(Z^{(0)}) + \mathcal{O}(p^{\mathrm{d}(i_*,0) + 1 - |I|})
 
\end{align*}
 
Note that when we refer to an interval $[a,b]$ on the circle we could be referring to two possible intervals because of the periodicity of the circle. In the following, whenever we refer to an interval $[a,b]$ we refer to the interval with vertex 0 on the \emph{inside}.
 
Here, I (Tom) tried to set do the same Lemma but for the circle instead of the infinite chain.
 
\begin{lemma}[Startingstate dependence] \label{lemma:probIndepCircle}
 
    Let $d(a,b)$ be the distance between $a,b\in[n]$ on the circle, so $d(a,b)=\min(|a-b| , n-|a-b|)$. Let $\dist{s}(a,b)$ be the distance between $a,b$ when taking the path that does \emph{not} cross $s$. Let $I\subseteq [n]$ be a non-empty set of vertices. Let $i_* \in I$ and define $I' = I \setminus \{i_*\}$. Let $j,s\notin I$, with $j\neq s$ be any vertices not in $I$.
 
    Then
 
    \begin{align*}
 
        \P_{I}(\Z{j})        &= \P_{I'}(\Z{j})        + \mathcal{O}(p^{d(i_*,j) + 1 - |I|}) \\
 
        \P_{I}(\Z{j},\NZ{s}) &= \P_{I'}(\Z{j},\NZ{s}) + \mathcal{O}(p^{\dist{s}(i_*,j) + 1 - |I|}) .
 
    \end{align*}
 
\end{lemma}
 
\begin{proof}
 
    We will prove both statements inductively on $|I|$. For $|I|=1$ we have $I=\{i_*\}$ and $I'=\emptyset$, so $\P_{I'}(\Z{j})=0$ and
 
    \begin{align*}
 
        \P_{I}(\Z{j})       &= \mathcal{O}(p^{d(i_*,j)}) \\
 
        \P_{I}(\Z{j},\NZ{s}) &= \mathcal{O}(p^{\dist{s}(i_*,j)})
 
    \end{align*}
 
    simply because a chain of zeroes has to be formed between $i_*$ and $j$, and in the second case this chain can not go through $s$. Now assume both statements hold up to $|I|-1$, then we prove them both for sets of size $|I|$.
 

	
 
For $a,b\in[n]$, define the event ``zeroes patch'' as the event of getting zeroes inside the interval $[a,b]$ but not on the boundary, i.e.  $\mathrm{ZP}^{[a,b]} = \mathrm{NZ}^{(a)} \cap \mathrm{Z}^{(a+1)} \cap \mathrm{Z}^{(a+2)} \cap \cdots \cap \mathrm{Z}^{(b-1)} \cap \mathrm{NZ}^{(b)}$ (where we assume that $\mathrm{Z}^{(0)}$ is part of this intersection).
 
    When we refer to an interval $[a,b]$ on the circle we could be referring to two possible intervals because of the periodicity of the circle. Define $[a,b]_j$ as the interval with vertex $j$ on the \emph{inside}. Furthermore by $-a$ we mean the vertex $n-a$, as one would expect modulo $n$.
 
    %If we refer to only $[a,b]$ then we mean $\{a,a+1,...,b\}$ where numbers are considered modulo $n$. So $[a,b]$ and $[b,a]$ are different intervals that cover the circle together.
 

	
 
Furthermore, define the `inside' and `outside' of $I$ as $I_{\mathrm{in}(a,b)} = I\cap[a,b]$ and $I_{\mathrm{out}(a,b)} = I \setminus [a,b]$.
 
The following diagram illustrates these definitions.
 
\begin{center}
 
    \includegraphics{diagram_circle_lemma.pdf}
 
\end{center}
 
\begin{align*}
 
    P_{I}(\mathrm{Z}^{(0)})
 
    &=\sum_{\substack{l,k=1\\k+l<n}}
 
    P_I(\mathrm{ZP}^{[n-l,k]}) \tag{the events are a partition}\\
 
    &=\sum_{\substack{l,k=1\\k+l<n\\k,n-l\notin I}}
 
    P_I(\mathrm{ZP}^{[n-l,k]}) \tag{$\mathbb{P}(\mathrm{ZP}^{[a,b]})=0$ for $a\in I$ or $b\in I$}
 
\end{align*}
 
Note that if $[-l,k]$ does not `touch' $I$ then $P_I(\mathrm{ZP}^{[-l,k]}) = 0$.
 
Furthermore, we have $P_I(\mathrm{ZP}^{[n-l,k]}) = \mathcal{O}(p^{k+l-1-|I_{\mathrm{in}(n-l,k)}|})$. If $k > \mathrm{d}(i_*,0)$ or $l > \mathrm{d}(i_*,0)$ then this gives $P_I(\mathrm{ZP}^{[n-l,k]}) = \mathcal{O}(p^{\mathrm{d}(i_*,0) + 1 - |I|})$ since $|I_\mathrm{in}| \leq |I|$. Therefore we have
 
\begin{align*}
 
    P_I(\mathrm{Z}^{(0)})
 
    &=\sum_{\substack{l,k=1\\k,n-l\notin I}}^{i_*-1}
 
    P_I(\mathrm{ZP}^{[n-l,k]})
 
    + \mathcal{O}(p^{i_* + 1 - |I|}) \\
 
    &=\sum_{\substack{l,k=1\\k,n-l\notin I}}^{i_*-1}
 
    P_{I_{\mathrm{in}(n-l,k)}}(\mathrm{ZP}^{[n-l,k]}) \cdot
 
    P_{I_{\mathrm{out}(n-l,k)}}(\mathrm{NZ}^{(n-l,k)})
 
    + \mathcal{O}(p^{i_* + 1 - |I|}) \\
 
    \tag{by Claim~\ref{claim:eventindependence} for $n-l,k\notin I$} \\
 
    &=\sum_{\substack{l,k=1\\k,n-l\notin I}}^{i_*-1}
 
    P_{I'_{\mathrm{in}(n-l,k)}}(\mathrm{ZP}^{[n-l,k]}) \cdot
 
    P_{I_{\mathrm{out}(n-l,k)}}(\mathrm{NZ}^{(n-l,k)})
 
    + \mathcal{O}(p^{i_* + 1 - |I|})
 
\end{align*}
 
Now we are supposed to use the induction step, but this is where I got stuck.
 
    Without loss of generality, we can assume that $0=j < i_* < s < n$. We will now consider intervals around vertex 0.
 
    For $l,r\geq 1$ and $l+r\leq n$, define the event ``zeroes patch'' $\mathrm{ZP}^{[-l,r]_0}$ as the event of getting zeroes inside the interval $[-l,r]_0$ but not on the boundary, i.e.
 
    $$\mathrm{ZP}^{[-l,r]_0} = \NZ{-l} \cap \Z{-l+1} \cap \cdots \cap \Z{0} \cap \cdots \cap \Z{r-1} \cap \NZ{r}$$
 
    Note that there are $r+l-1$ `zeroes' in this event, so $\P_{J}(\mathrm{ZP}^{[-l,r]_0}) = \mathcal{O}(p^{r+l-1-|J|})$ for $J\subseteq[-l,r]_0$.
 
    Claim:
 
    \begin{align*}
 
        \P_{I}(\mathrm{ZP}^{[-l,r]_0}) &= \P_{I'}(\mathrm{ZP}^{[-l,r]_0})
 
        + \mathcal{O}(p^{\min\left( \dist{r}(i_*,-l) , d(i_*,r)\right)+l+r-|I|})
 
    \end{align*}
 
    \todo{These special cases.}
 
    If $r\geq i_*$ or $l\geq n-i_*$ then $\P_{I}(\mathrm{ZP}^{[-l,r]_0}) = \mathcal{O}(p^{d(i_*,0) + 1 - |I|})$.
 
    If $-l\in I$ or $r\in I$ then the left hand side is zero so the claim holds.
 
    If $[-l,r]_0$ has no overlap with $I$ then both sides of the above expression are zero so it also holds. We are left with the case where, $-l,r,\notin I$ and $[-l,r]_0 \cap I \neq \emptyset$ and $i_*\notin[-l,r]_0$.
 
    The following diagram illustrates the situation
 
    \begin{center}
 
        \includegraphics{diagram_circle_lemma.pdf}
 
    \end{center}
 
    Note that by Claim~\ref{claim:eventindependence} we have
 
    \begin{align*}
 
        \P_{I}(\mathrm{ZP}^{[-l,r]_0}) = \P_{I \cap [-l,r]_0}(\mathrm{ZP}^{[-l,r]_0}) \;\cdot\; \P_{I\setminus [-l,r]_0}(\NZ{a},\NZ{b})
 
    \end{align*}
 
    We have $i_*\in I \setminus[-l,r]_0$, and $I\cap[-l,r]_0 = I' \cap [-l,r]_0$. Define $J=I\setminus[-l,r]_0$ and $J'=I'\setminus[-l,r]_0$. We have $|J|<|I|$ so we can apply the induction hypothesis to $J$:
 
    \begin{align*}
 
        \P_{J}(\NZ{-l},\NZ{r})
 
        &=
 
        1
 
        - \P_{J}(\Z{-l},\NZ{r})
 
        - \P_{J}(\Z{r})
 
        \tag{partition of all events} \\
 
        &=
 
        1
 
        - \P_{J'}(\Z{-l},\NZ{r})
 
        - \P_{J'}(\Z{r}) \\
 
        &\quad + \mathcal{O}(p^{\dist{r}(i_*,-l)+1-|J|})
 
        + \mathcal{O}(p^{d(i_*,r)+1-|J|}) \\
 
        &=
 
        \P_{J'}(\NZ{-l},\NZ{b})
 
        + \mathcal{O}(p^{\min\left( \dist{r}(i_*,-l) , d(i_*,r)\right)+1-|J|})
 
    \end{align*}
 
    Note that the event $\mathrm{ZP}^{[-l,r]_0}$ contains $l+r-1$ zeroes, so $\P_{I \cap [-l,r]_0}(\mathrm{ZP}^{[-l,r]_0}) = \mathcal{O}(p^{l+r-1-|I\cap[-l,r]_0|})$. This means
 
    \begin{align*}
 
        \P_{I}(\mathrm{ZP}^{[-l,r]_0})
 
        &= \P_{I' \cap [-l,r]_0}(\mathrm{ZP}^{[-l,r]_0})
 
        \left( \P_{I' \setminus [-l,r]_0}(\NZ{a},\NZ{b}) + \mathcal{O}(p^{\min\left( \dist{r}(i_*,-l) , d(i_*,r)\right)+1-|J|}) \right) \\
 
        &= \P_{I' \cap [-l,r]_0}(\mathrm{ZP}^{[-l,r]_0}) \;\cdot\; \P_{I'\setminus [-l,r]_0}(\NZ{a},\NZ{b}) \\
 
        &\qquad + \mathcal{O}(p^{\min\left( \dist{r}(i_*,-l) , d(i_*,r)\right)+1-|J| + l+r-1-|I\cap[-l,r]_0|}) \\
 
        &= \P_{I'}(\mathrm{ZP}^{[-l,r]_0})
 
        + \mathcal{O}(p^{\min\left( \dist{r}(i_*,-l) , d(i_*,r)\right)+l+r-|I|})
 
    \end{align*}
 
    Case separation shows that $\min\left( \dist{r}(i_*,-l) , d(i_*,r)\right) \geq d(i_*,0) + 1$ \todo{prove.}
 

	
 
    Now we can prove the required equalities:
 
    \begin{align*}
 
        \P_{I}(\Z{0})
 
        &=\sum_{\substack{l,r\geq 1\\l+r\leq n}}
 
        \P_I(\mathrm{ZP}^{[-l,r]_0})
 
        \tag{the events are a partition of $\Z{0}$}\\
 
        &=\sum_{\substack{l,r\geq 1\\l+r\leq n}}
 
        \P_{I'}(\mathrm{ZP}^{[-l,r]_0})
 
        + \mathcal{O}(p^{\min\left( \dist{r}(i_*,-l) , d(i_*,r)\right)+l+r-|I|}) \\
 
        &= \P_{I'}(\Z{0}) + \mathcal{O}(p^{d(i_*,0)+1-|I|})
 
    \end{align*}
 
    Similarly, we have
 
    \begin{align*}
 
        \P_{I}(\Z{0} , \NZ{s})
 
        &=\sum_{l=1}^{n-s}\sum_{r=1}^{s}
 
        \P_{I}(\mathrm{ZP}^{[-l,r]_0},\NZ{s})
 
        \tag{partition of $\Z{0}$}\\
 
        &=\sum_{l=1}^{n-s}\sum_{r=1}^{s}
 
        \P_{I'}(\mathrm{ZP}^{[-l,r]_0},\NZ{s})
 
        + \mathcal{O}(p^{something}) \\
 
        &= \P_{I'}(\Z{0} , \NZ{s})
 
        + \sum_{l=1}^{n-s}\sum_{r=1}^{s} + \mathcal{O}(p^{something})
 
    \end{align*}
 
    \todo{finish details}
 
\end{proof}
 

	
 
\begin{definition}[Connected patches]
 
	Let $\mathcal{P}\subset 2^{\mathbb{Z}}$ be a finite system of finite subsets of $\mathbb{Z}$. We say that the patch set of a resample sequence is $\mathcal{P}$,
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