Characterization of eccentric digraphs

AbstractThe eccentric digraph ED(G) of a digraph G represents the binary relation, defined on the vertex set of G, of being ‘eccentric’; that is, there is an arc from u to v in ED(G) if and only if v is at maximum distance from u in G. A digraph G is said to be eccentric if there exists a digraph H such that G=ED(H). This paper is devoted to the study of the following two questions: what digraphs are eccentric and when the relation of being eccentric is symmetric.We present a characterization of eccentric digraphs, which in the undirected case says that a graph G is eccentric iff its complement graph G¯ is either self-centered of radius two or it is the union of complete graphs. As a consequence, we obtain that all trees except those with diameter 3 are eccentric digraphs. We also determine when ED(G) is symmetric in the cases when G is a graph or a digraph that is not strongly connected

A Survey on eccentric digraphs of (di)graphs

The eccentricity e(u) of a vertex u is the maximum distance of u to any other vertex of G. A vertex v is an eccentric vertex of vertex u if the distance from u to v is equal to e(u). The eccentric digraph ED(G) of a graph(digraph) G is the digraph that has the same vertex as G and an arc from u to v exists in ED(G) if and only if v is an eccentric vertex of u in G. In this survey we take a look on the progress made till date in the theory of Eccentric digraphs of graphs and digraphs, in general. And list the open problems in the area

Eccentric digraphs

AbstractThe distance d(u,v) from vertex u to vertex v in a digraph G is the length of the shortest directed path from u to v. The eccentricity e(v) of vertex v is the maximum distance of v to any other vertex of G. A vertex u is an eccentric vertex of vertex v if the distance from v to u is equal to the eccentricity of v. The eccentric digraph ED(G) of a digraph G is the digraph that has the same vertex set as G and the arc set defined by: there is an arc from u to v iff v is an eccentric vertex of u. The idea of the eccentric digraph of a graph was introduced by Buckley (Congr. Numer. 149 (2001) 65) and the idea of the eccentric digraph of a digraph by Boland and Miller (Proceedings of AWOCA’01, July 2001, p. 66). In this paper, we examine eccentric digraphs of digraphs for various families of digraphs and we consider the behaviour of an iterated sequence of eccentric digraphs of a digraph. The paper concludes with several open problems

Products and Eccentric digraphs

The eccentricity e(u) of a vertex u is the maximum distance of u to any other vertex of G. A vertex v is an eccentric vertex of vertex u if the distance from u to v is equal to e(u). The eccentric digraph ED(G) of a graph(digraph) G is the digraph that has the same vertex as G and an arc from u to v exists in ED(G) if and only if v is an eccentric vertex of u in G. In this paper, we consider the eccentric digraphs of different products of graphs, viz., cartesian, normal, lexicographic, prism, et

Products and Eccentric Diagraphs

The eccentricity e(u) of a vertex u is the maximum distance of u to any other vertex of G. A vertex v is an eccentric vertex of vertex u if the distance from u to v is equal to e(u). The eccentric digraph ED(G) of a graph(digraph) G is the digraph that has the same vertex as G and an arc from u to v exists in ED(G) if and only if v is an eccentric vertex of u in G. In this paper, we consider the eccentric digraphs of different products of graphs, viz., cartesian, normal, lexicographic, prism, etc

Distance Degree Regular Graphs and Theireccentric Digraphs

The eccentricity e(u) of a vertex u is the maximum distance of u to any other vertex of G.The distance degree sequence (dds) of a vertex v in a graph G = (V,E) is a list of the number of vertices at distance 1, 2, . . . , e(u) in that order, where e(u) denotes the eccentricity of v in G. Thus the sequence (di0 , di1 , di2 , . . . , dij , . . .) is the dds of the vertex vi in G where dij denotes number of vertices at distance j from vi. A graph is distance degree regular (DDR) graph if all vertices have the same dds. A vertex v is an eccentric vertex of vertex u if the distance from u to v is equal to e(u). The eccentric digraph ED(G) of a graph (digraph) G is the digraph that has the same vertex as G and an arc from u to v exists in ED(G) if and only if v is an eccentric vertex of u in G. In this paper, we consider the construction of new families of DDR graphs with arbitrary diameter. Also we consider some special class of DDR graphs in relation with eccentric digraph of a graph. Different structural properties of eccentric digraphs of DDR graphs are dealt herewith

Distance Degree Regular Graphs and Distance Degree Injective Graphs: An Overview

The distance d ( v , u ) from a vertex v of G to a vertex u is the length of shortest v to u path. The eccentricity e v of v is the distance to a farthest vertex from v . If d ( v , u ) = e ( v ) , ( u ≠ v ) , we say that u is an eccentric vertex of v . The radius rad ( G ) is the minimum eccentricity of the vertices, whereas the diameter diam ( G ) is the maximum eccentricity. A vertex v is a central vertex if e ( v ) = r a d ( G ) , and a vertex is a peripheral vertex if e ( v ) = d i a m ( G ) . A graph is self-centered if every vertex has the same eccentricity; that is, r a d ( G ) = d i a m ( G ) . The distance degree sequence (dds) of a vertex v in a graph G = ( V , E ) is a list of the number of vertices at distance 1 , 2 , . . . . , e ( v ) in that order, where e ( v ) denotes the eccentricity of v in G . Thus, the sequence ( d i 0 , d i 1 , d i 2 , … , d i j , … ) is the distance degree sequence of the vertex v i in G where d i j denotes the number of vertices at distance j from v i . The concept of distance degree regular (DDR) graphs was introduced by Bloom et al., as the graphs for which all vertices have the same distance degree sequence. By definition, a DDR graph must be a regular graph, but a regular graph may not be DDR. A graph is distance degree injective (DDI) graph if no two vertices have the same distance degree sequence. DDI graphs are highly irregular, in comparison with the DDR graphs. In this paper we present an exhaustive review of the two concepts of DDR and DDI graphs. The paper starts with an insight into all distance related sequences and their applications. All the related open problems are listed

DIGRAF EKSENTRIK DARI GRAF COCKTAIL PARTY

Misal G adalah suatu graf dengan himpunan vertex V(G) dan himpunan vertex E(G) . Jarak dari vertex u ke vertex v di G, dinotasikan d(u,v), adalah panjang dari path terpendek dari vertex u ke v. Eksentrisitas vertex u dalam graf G adalah jarak maksimum dari vertex u ke sebarang vertex yang lain di G, dinotasikan e(u). Vertex v adalah suatu vertex eksentrik dari u jika d(u,v) = e(u). Digraf eksentrik ED(G) dari suatu graf G adalah suatu graf yang mempunyai himpunan vertex yang sama dengan himpunan vertex G, dan terdapat suatu arc (edge berarah) yang menghubungkan vertex u ke v jika v adalah suatu vertex eksentrik dari u. Dalam makalah ini diselidiki digraf eksentrik dari suatu kelas graf yaitu graf cocktail party H m , n , untuk m = 2 . Kata kunci : eksentrisitas, digraf eksentrik, graf cocktail part

DIGRAF EKSENTRIK DARI GRAF GEAR

Diberikan G dengan himpunan berhingga vertex V(G) dan himpunan edge E(G). Jarak dari vertex u ke vertex v di G, dinotasikan d(u,v), adalah panjang dari path terpendek dari vertex u ke v. Eksentrisitas vertex u dalam graf G adalah jarak maksimum dari vertex u ke sebarang vertex yang lain di G, dinotasikan e(u). Vertex v disebut vertex eksentrik dari u jika d(u,v) = e(u). Sedangkan untuk menentukan jarak dari vertex u ke sembarang vertex v dalam graf G digunakan algoritma Breadth First Search (BFS) Moore yang diambil dari Chartrand dan Oellermann [3]. Digraf eksentrik ED(G) dari suatu graf G adalah suatu graf yang mempunyai himpunan vertex yang sama dengan himpunan vertex G, dan terdapat suatu arc (edge berarah) yang menghubungkan vertex u ke v jika v adalah suatu vertex eksentrik dari u. Boland dan Miller [1] memperkenalkan digraf eksentrik dari suatu digraf. Mereka memberi saran untuk menemukan digraf ekesentrik dari bermacam kelas graf. Di sini diselidiki digraf eksentrik dari salah satu kelas graf yaitu graf gear. Kata kunci: eksentrisitas, digraf eksentrik, graf gear