In this paper we give a characterization of kernel-perfect (and of critical kernel-imperfect) arc-local tournament digraphs. As a consequence, we prove that arc-local tournament digraphs satisfy a strenghtened form of the following interesting conjecture which constitutes a bridge between kernels and perfectness in digraphs, stated by C. Berge and P. Duchet in 1982: a graph G is perfect if and ...

In this article, we present a characterization of basic graphs in terms of forbidden induced subgraphs. This class of graphs was introduced by Conforti, Cornuéjols and Vušković [3], and it plays an essential role in the announced proof of the Strong Perfect Graph Conjecture by Chudnovsky, Robertson, Seymour and Thomas [2]. Then we apply the Reducing Pseudopath Method [13] to characterize the su...

The concept of the strongest path plays a crucial role in fuzzy graph theory. In classical graph theory, all paths in a graph are strongest, with a strength value of one. In this article, we introduce Menger’s theorem for fuzzy graphs and discuss the concepts of strengthreducing sets and t-connected fuzzy graphs. We also characterize t-connected and t-arc connected fuzzy graphs. 2012 Elsevier I...

In this paper we study strongest paths in a fuzzy graph. A necessary and sufficient condition for an arc in a fuzzy graph to be a strongest path and a sufficient condition for a path in a fuzzy graph to be a strongest path are obtained. A characterization of δ−arcs and the relationship between fuzzy cutnodes and δ−arcs are also obtained. Also a characterization of blocks is obtained using stron...

In the present paper, we study some properties of fuzzy norm of linear operators. At first the bounded inverse theorem on fuzzy normed linear spaces is investigated. Then, we prove Hahn Banach theorem, uniform boundedness theorem and closed graph theorem on fuzzy normed linear spaces. Finally the set of all compact operators on these spaces is studied.

The Wonderful Lemma, that was first proved by Roussel and Rubio, is one of the most important tools in the proof of the Strong Perfect Graph Theorem. Here we give a short proof of this lemma.

We give sufficient conditions for a tripartite graph to have a spanning subgraph consisting of complete graphs of order 3. This is applied to bound the strong chromatic number of a graph.

In this paper, integrity of fuzzy graph is defined. Integrity of special types of graphs with constant node strength and node strength sequences as (pn−1 1 , p2) is discussed. Also, integrity of regular fuzzy graph and complete fuzzy graph is presented.