An edge-coloring of a graph G with colors 1, . . . , t is an interval t-coloring if all colors are used, and the colors of edges incident to each vertex of G are distinct and form an interval of integers. A graph G is interval colorable if it has an interval t-coloring for some positive integer t. The problem of deciding whether a bipartite graph is interval colorable is NP-complete. The smalle...

let g be a finite group and let $gk(g)$ be the prime graph of g. we assume that $n$ is an odd number. in this paper, we show that if $gk(g)=gk(b_n(p))$, where $ngeq 9$ and $pin {3,5,7}$, then g has a unique nonabelian composition factor isomorphic to $b_n(p)$ or $c_n(p)$ . as consequences of our result, $b_n(p)$ is quasirecognizable by its spectrum and also by a new proof, the validity of a con...

The present paper studies local distributed graph problems in highly dynamic networks. We define a (in our view) natural generalization of static graph problems to the dynamic graph setting. For some parameter T > 0, the set of admissible outputs of nodes in a T -dynamic solution for a given graph problem at some time t is defined by the dynamic graph topology in the time interval [t − T, t]. T...

in this paper we will prove that the simple group g2(q) where 2 < q = 1(mod3)is recognizable by the set of its order components, also other word we prove that if g is anite group with oc(g) = oc(g2(q)), then g is isomorphic to g2(q).

A dominating set of a graph G is vertices that contains at least one endpoint every edge on the graph. The domination number order minimum G. (t, r) broadcast generalization in which broadcasting emits signals strength t decrease by 1 as they traverse each edge, and we require vertex receives cumulative signal r from its neighbors. In this paper, extend study to directed graphs. Our main result...

The interval number of a graph G is the least natural number t such that G is the intersection graph of sets, each of which is the union of at most t intervals, denoted by i (G ). Griggs and West showed that i(G) d12(d þ 1)e. We describe the extremal graphs for that inequality when d is even. For three special perfect graph classes we give bounds on the interval number in terms of the independe...