### Finite Volume Spaces and SparsificationFinite Volume Spaces and Sparsification

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 Author Newman, Ilan ♦ Rabinovich, Yuri Source arXiv.org Content type Text File Format PDF Date of Submission 2010-02-18 Language English
 Subject Domain (in DDC) Computer science, information & general works Subject Keyword Computer Science - Data Structures and Algorithms ♦ Computer Science - Discrete Mathematics ♦ G.2.0 ♦ G.2.1 ♦ F.2.2 ♦ cs Abstract We introduce and study finite $d$-volumes - the high dimensional generalization of finite metric spaces. Having developed a suitable combinatorial machinery, we define $\ell_1$-volumes and show that they contain Euclidean volumes and hypertree volumes. We show that they can approximate any $d$-volume with $O(n^d)$ multiplicative distortion. On the other hand, contrary to Bourgain's theorem for $d=1$, there exists a $2$-volume that on $n$ vertices that cannot be approximated by any $\ell_1$-volume with distortion smaller than $\tilde{\Omega}(n^{1/5})$. We further address the problem of $\ell_1$-dimension reduction in the context of $\ell_1$ volumes, and show that this phenomenon does occur, although not to the same striking degree as it does for Euclidean metrics and volumes. In particular, we show that any $\ell_1$ metric on $n$ points can be $(1+ \epsilon)$-approximated by a sum of $O(n/\epsilon^2)$ cut metrics, improving over the best previously known bound of $O(n \log n)$ due to Schechtman. In order to deal with dimension reduction, we extend the techniques and ideas introduced by Karger and Bencz{\'u}r, and Spielman et al.~in the context of graph Sparsification, and develop general methods with a wide range of applications. Educational Use Research Learning Resource Type Article