A graph G of order n is called arbitrarily vertex decomposable if for each sequence (a1, . . . , ak) of positive integers such that a1+. . .+ak = n there exists a partition (V1, . . . , Vk) of the vertex set of G such that for each i ∈ {1, . . . , k}, Vi induces a connected subgraph of G on ai vertices. D. Barth and H. Fournier showed that if a tree T is arbitrarily vertex decomposable, then T ...

A graph is called degree-magic if it admits a labelling of the edges by integers 1, 2, . . . , |E(G)| such that the sum of the labels of the edges incident with any vertex v is equal to 1+|E(G)| 2 deg(v). Degree-magic graphs extend supermagic regular graphs. In this paper we characterize complete tripartite degree-magic graphs.

For any h ∈ Z, a graph G = (V, E) is said to be h-magic if there exists a labeling l : E(G) → Zh−{0} such that the induced vertex set labeling l : V (G) → Zh defined by l(v) = ∑ uv∈E(G) l(uv) is a constant map. For a given graph G, the set of all h ∈ Z+ for which G is h-magic is called the integermagic spectrum of G and is denoted by IM (G). In this paper, we will determine the integer-magic sp...

We propose a Bayesian approximate inference method for learning the dependence structure of a Gaussian graphical model. Using pseudo-likelihood, we derive an analytical expression to approximate the marginal likelihood for an arbitrary graph structure without invoking any assumptions about decomposability. The majority of the existing methods for learning Gaussian graphical models are either re...

Finding clusters of well-connected nodes in a graph is a problem common to many domains, including social networks, the Internet and bioinformatics. From a computational viewpoint, finding these clusters or graph communities is a difficult problem. We use a clique matrix decomposition based on a statistical description that encourages clusters to be well connected and few in number. The formal ...

We answer a question of Brandstädt et al. by showing that deciding whether a line graph with maximum degree 5 has a stable cutset is NP -complete. Conversely, the existence of a stable cutset in a line graph with maximum degree at most 4 can be decided efficiently. The proof of our NP -completeness result is based on a refinement on a result due to Chvátal that recognizing decomposable graphs w...

This survey emphasises results in graph theory which were fairly difficult to prove. Because it is a personal view of the subject, this section will describe three of my own results which I personally found fairly difficult to prove (whatever their degree of difficulty in an absolute sense may be). A decomposition of a graph G is a set of subgraphs of G such that each edge of G belongs to exact...

SUPER MAGIC AND ANTIMAGIC LABELINGS OF DISJOINT UNION OF PLANE GRAPHS Ali Ahmad, Martin Bača, Marcela Lascsáková, Andrea Semaničová-Feňovčíková 2,3 College of computer and information system, Jazan University, Jazan, Saudi Arabia Department of Appl. Mathematics and Informatics, Technical University, Košice, Slovak Republic Abdus Salam School of Mathematical Sciences, G. C. University, Lahore, P...

A vertex magic total labeling on a graph with v vertices and e edges is a one to one map taking the vertices and edges onto the integers with the property that the sum of the label on the vertex and the labels of its incident edges is a constant, independent of the choice of the vertex. A graph with vertex magic total labeling with two constants or is called a vertex bimagic total labeling. The...