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Full-Text Articles in Physical Sciences and Mathematics
Sparse Hypergraphs And Pebble Game Algorithms, Ileana Streinu, Louis Theran
Sparse Hypergraphs And Pebble Game Algorithms, Ileana Streinu, Louis Theran
Computer Science: Faculty Publications
A hypergraph G=(V,E) is (k,ℓ)-sparse if no subset V′⊂V spans more than k|V′|−ℓ hyperedges. We characterize (k,ℓ)-sparse hypergraphs in terms of graph theoretic, matroidal and algorithmic properties. We extend several well-known theorems of Haas, Lovász, Nash-Williams, Tutte, and White and Whiteley, linking arboricity of graphs to certain counts on the number of edges. We also address the problem of finding lower-dimensional representations of sparse hypergraphs, and identify a critical behavior in terms of the sparsity parameters k and ℓ. Our constructions extend the pebble games of Lee and Streinu [A. Lee, I. Streinu, Pebble game algorithms …
Some Properties Of Yao Y4 Subgraphs, Joseph O'Rourke
Some Properties Of Yao Y4 Subgraphs, Joseph O'Rourke
Computer Science: Faculty Publications
The Yao graph for k = 4, Y4, is naturally partitioned into four subgraphs, one per quadrant. We show that the subgraphs for one quadrant differ from the subgraphs for two adjacent quadrants in three properties: planarity, connectedness, and whether the directed graphs are spanners.