Let tw(G), pw(G), c(G), !J.(G) denote, respectively, the tree-width, path-width, cutwidth and the maximum degree of a graph G on 11 vertices . It is known that c (G)~tw (G). We prove that c (G) =0 (tw (G)·!J.(G)·logn), and if ({Xj : iel] ,T=(I,A» is a tree decomposition of G with tree-wid~ then c (G) S (k+ l)·!J.(G)·c (T). In case that a tree decomposition is given, or that the tree-width is bo...

abstract the oak leafroller moth , tortrix viridana l. is a destructive pest within it’s spreading area which invades the oak species, especially in west and northwest forests of iran, in recent years. some parts of west azarbayjan’s forests which are located in piranshahr and sardasht region have been affected by this pest since 1989 that oak trees vigor and survival have been gone down result...

We prove that for any fixed r ≥ 2, the tree-width of graphs not containing Kr as a topological minor (resp. as a subgraph) is bounded by a linear (resp. polynomial) function of their rank-width. We also present refinements of our bounds for other graph classes such as Kr-minor free graphs and graphs of bounded genus.

Disjunctive Answer Set Programming (ASP) is a powerful declarative programming paradigm whose main decision problems are located on the second level of the polynomial hierarchy. Identifying tractable fragments and developing efficient algorithms for such fragments are thus important objectives in order to complement the sophisticated ASP systems available to date. Hard problems can become tract...

Tree-width and clique-width are two important graph complexity measures that serve as parameters in many fixed-parameter tractable (FPT) algorithms. The same classes of sparse graphs, in particular of planar graphs and of graphs of bounded degree have bounded tree-width and bounded clique-width. We prove that, for sparse graphs, clique-width is polynomially bounded in terms of tree-width. For p...