an:06937767
Zbl 1395.05116
Jeong, Jisu; S??ther, Sigve Hortemo; Telle, Jan Arne
Maximum matching width: new characterizations and a fast algorithm for dominating set
EN
Discrete Appl. Math. 248, 114-124 (2018).
00414462
2018
j
05C62 05C85 05C69 68Q25
treewidth; branchwidth; maximum matching width; minimum dominating set problem
Summary: A graph of treewidth \(k\) has a representation by subtrees of a ternary tree, with subtrees of adjacent vertices sharing a tree node, and any tree node sharing at most \(k + 1\) subtrees. Likewise for branchwidth, but with a shift to the edges of the tree rather than the nodes. In this paper we show that the mm-width of a graph -- maximum matching width -- combines aspects of both these representations, targeting tree nodes for adjacency and tree edges for the parameter value. The proof of this new characterization of mm-width is based on a definition of canonical minimum vertex covers of bipartite graphs. We show that these behave in a monotone way along branch decompositions over the vertex set of a graph.
We use these representations to compare mm-width with treewidth and branchwidth, and also to give another new characterization of mm-width, by subgraphs of chordal graphs. We prove that given a graph \(G\) and a branch decomposition of maximum matching width \(k\) we can solve the Minimum Dominating Set Problem in time \(O^\ast(8^k)\), thereby beating \(O^\ast(3^{\mathrm{tw}(G)})\) whenever \(\mathrm{tw}(G) > \log_3 8 \times k \approx 1.893 k\). Note that \(\mathrm{mmw}(G) \leq \mathrm{tw}(G) + 1 \leq 3 \mathrm{mmw}(G)\) and these inequalities are tight. Given only the graph \(G\) and using the best known algorithms to find decompositions, maximum matching width will be better for minimum dominating set whenever \(\mathrm{tw}(G) > 1.549 \times \mathrm{mmw}(G)\).