nearly uniform sparsest cut

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2025-05-28 18:43:03 +08:00
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@@ -193,6 +193,15 @@ I think the intuition behind this SDP relaxation is almost the same as \metric{}
The Lasserre relaxation of SDP automatically satisfies 1 and 2. But I believe there may be some very strange kind of metric that embeds into $\ell_1$ well?
Another possible approach for \nonuscut{} would be making the number of demand vertices small and then applying a metric embedding (contraction) to $\ell_1$ with better distortion on those vertices.
\section{Nealy uniform \scut{}}
What is the best approximation ratio for \uscut{} instances where almost all demands are uniform.
More formally, consider a \nonuscut{} instance where only $k$ vertices are associated with demand pairs with $D_i\neq 1$,
we want to show that we can approximate nearly uniform \scut{} in polynomial time to ratio $O(\sqrt{\log n}f(k))$, where $f(k)=O(\log \log n)$ when $k\to n$.
Let those $k$ non uniform vertices be outliers.
\cite{arora_expander_2004} shows that for non-outlier verteices the optimal solution to SDP (a metric) can be embedded into $\ell_1$ with distortion $\sqrt{\log n}$.
\cite{chawla_composition_2023} is a recent result on getting approximate $(k,c)$-outlier embeddings.
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