“…Graph Sparsification. Graph sparsification was introduced by Benczúr and Karger [8] ("for-all" cut sparsfiers), and has led to research in a number of directions: Fung et al [17] and Kapralov and Panigrahy [27] gave new algorithms for preserving cuts in a sparsifier; Spielman and Teng [46] generalized to spectral sparsfiers that preserved all quadratic forms, which led to further research both in improving the bounds on the size of the sparsifier [45,7] and also in the running time of spectral sparsification algorithms (e.g., [35,5,36,11,34,31,33,32]); faster algorithms for fundamental graph problems such as maximum flow utilized sparsification results (e.g., [8,43]); Ahn and Guha [1] introduced sparsification in the streaming model, which has led to a large body of work for both cut sparifiers (e.g., [2,3,18]) and spectral sparsifiers (e.g., [26,25,24,4]) in graph streams; both cut [30,40] and spectral [44] sparsification have been studied in hypergraphs; etc. For lower bounds, Andoni et al [6] showed that any data structure that (1± )-approximately stores the sizes of all cuts in an undirected graph must use Ω(n/ 2 ) bits.…”