Subsemi-Eulerian graphs.
Soit le -ième nombre premier. Une fonction arithmétique complètement additive est définie sur par la donnée des et la formule , où désigne la...
The basis number of a graph was defined by Schmeichel to be the least integer such that has an -fold basis for its cycle space. He proved that for , the basis number of the complete bipartite graph is equal to 4 except for , and with . We determine the basis number of some particular non-planar graphs such as and , , and -cages for , and the Robertson graph.
A set D of vertices in a graph G = (V,E) is a dominating set of G if every vertex in V-D is adjacent to some vertex in D. The domination number γ(G) of G is the minimum cardinality of a dominating set. We define the cobondage number of G to be the minimum cardinality among the sets of edges X ⊆ P₂(V) - E, where P₂(V) = X ⊆ V:|X| = 2 such that γ(G+X) < γ(G). In this paper, the exact values of bc(G) for some standard graphs are found and some bounds are obtained. Also, a Nordhaus-Gaddum type...
In a graph, by definition, the weight of a (proper) coloring with positive integers is the sum of the colors. The chromatic sum is the minimum weight, taken over all the proper colorings. The minimum number of colors in a coloring of minimum weight is the cost chromatic number or strength of the graph. We derive general upper bounds for the strength, in terms of a new parameter of representations by edge intersections of hypergraphs.
An edge ordering of a graph G is an injection f : E(G) → R, the set of real numbers. A path in G for which the edge ordering f increases along its edge sequence is called an f-ascent ; an f-ascent is maximal if it is not contained in a longer f-ascent. The depression of G is the smallest integer k such that any edge ordering f has a maximal f-ascent of length at most k. A k-kernel of a graph G is a set of vertices U ⊆ V (G) such that for any edge ordering f of G there exists a maximal f-ascent of...
In this paper we continue the study of paired-domination in graphs introduced by Haynes and Slater (Networks 32 (1998), 199–206). A paired-dominating set of a graph with no isolated vertex is a dominating set of vertices whose induced subgraph has a perfect matching. The paired-domination number of , denoted by , is the minimum cardinality of a paired-dominating set of . The graph is paired-domination vertex critical if for every vertex of that is not adjacent to a vertex of degree one,...