gap 4 conj doesn't seem correct... fixed some setminus
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main.tex
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main.tex
@ -121,7 +121,7 @@ s.t.& & \sum_{e\in T} x_e+y_e&\geq 1 & &\forall T & &\text{($x+y$ is
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\begin{frame}{Normalized Mincut from LP}
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\begin{frame}{Normalized Mincut from LP}
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One standard trick for dealing LPs with knapsack constraints is to consider its Lagrangian dual.
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One standard trick for dealing LPs with knapsack constraints is to consider its Lagrangian dual.
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\begin{equation*}
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\begin{equation*}
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\max_{\mu\geq 0} L(\mu)= \max_{\mu\geq 0} \min \left\{ w(C-F)-\mu(b-c(F)) | \forall \text{cut $C$}\;\forall F\subset C
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\max_{\mu\geq 0} L(\mu)= \max_{\mu\geq 0} \min \left\{ w(C\setminus F)-\mu(b-c(F)) | \forall \text{cut $C$}\;\forall F\subset C
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% \land c(F)\leq b
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% \land c(F)\leq b
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\right\}
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\right\}
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\end{equation*}
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\end{equation*}
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@ -130,11 +130,11 @@ One standard trick for dealing LPs with knapsack constraints is to consider its
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$L(\mu)$ is piecewise linear and concave.
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$L(\mu)$ is piecewise linear and concave.
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\end{lemma}
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\end{lemma}
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For fixed $\mu$, how to solve $\min\limits_{C,F} \left\{ w(C-F)-\mu(b-c(F))
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For fixed $\mu$, how to solve $\min\limits_{C,F} \left\{ w(C\setminus F)-\mu(b-c(F))
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\right\}$?
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\right\}$?
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For small enough $\mu\geq 0$, $w(C-F)$ term is dominanting.
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For small enough $\mu\geq 0$, $w(C\setminus F)$ term is dominanting.
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Thus the optimal solution must be $C=F=\text{mincut with weight $c$}$.
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Thus the optimal solution must be $C=F=\text{mincut with capacity $c$}$.
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\end{frame}
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\end{frame}
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@ -144,7 +144,7 @@ We have see that the first line segment is $L(\mu)=(\lambda_c-b)\mu$ where $\lam
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What is the first breakpoint on $L(\mu)$?
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What is the first breakpoint on $L(\mu)$?
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\newline
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\newline
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We have $-\mu(b-\lambda_c)\leq w(C- F)-\mu(b-c(F))$ for any cut $C$ and $F\subsetneq C$. Thus the first breakpoint is $\mu=\min \frac{w(C- F)}{\lambda_c-c(F)}$, which is the value of normalized mincut.
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We have $-\mu(b-\lambda_c)\leq w(C\setminus F)-\mu(b-c(F))$ for any cut $C$ and $F\subsetneq C$. Thus the first breakpoint is $\mu=\min \frac{w(C\setminus F)}{\lambda_c-c(F)}$, which is the value of normalized mincut.
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\newline
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\newline
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What about other breakpoints?
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What about other breakpoints?
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@ -173,19 +173,19 @@ Again we first assume the $\mu$ is fixed. Then for each pair of constraints $\su
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\end{frame}
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\end{frame}
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\begin{frame}{Integrality Gap}
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\begin{frame}{Integrality Gap}
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\begin{conjecture}
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% \begin{conjecture}
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ILP\ref{IP} has an integrality gap of 4.
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% ILP\ref{IP} has an integrality gap of 4.
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\end{conjecture}
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% \end{conjecture}
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Suppose $\mu^*$ is the optimal solution to LP\ref{lp:dualcutint}. Let $\lambda^{fr}$ be the fractional mincut with capacity $w_\mu$.
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% Suppose $\mu^*$ is the optimal solution to LP\ref{lp:dualcutint}. Let $\lambda^{fr}$ be the fractional mincut with capacity $w_\mu$.
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we have
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% we have
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\begin{align*}
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% \begin{align*}
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4\opt(LP) &=4\lambda^{fr}-4b\mu^*\\
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% 4\opt(LP) &=4\lambda^{fr}-4b\mu^*\\
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&\geq 2\lambda^{int} - 4b\mu^*\\
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% &\geq 2\lambda^{int} - 4b\mu^*\\
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&\geq w_{\mu^*}(C^*)-b\mu^*,
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% &\geq w_{\mu^*}(C^*)-b\mu^*,
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\end{align*}
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% \end{align*}
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which implies Theorem \autoref{thm:2approx}.
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% which implies Theorem \autoref{thm:2approx}.
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\end{frame}
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\end{frame}
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\begin{frame}{References}
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\begin{frame}{References}
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\bibliographystyle{plainnat}
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\bibliographystyle{plainnat}
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