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Groups in which the prime graph is a tree

Maria Silvia Lucido (2002)

Bollettino dell'Unione Matematica Italiana

The prime graph Γ G of a finite group G is defined as follows: the set of vertices is π G , the set of primes dividing the order of G , and two vertices p , q are joined by an edge (we write p q ) if and only if there exists an element in G of order p q . We study the groups G such that the prime graph Γ G is a tree, proving that, in this case, π G 8 .

Grundy number of graphs

Brice Effantin, Hamamache Kheddouci (2007)

Discussiones Mathematicae Graph Theory

The Grundy number of a graph G is the maximum number k of colors used to color the vertices of G such that the coloring is proper and every vertex x colored with color i, 1 ≤ i ≤ k, is adjacent to (i-1) vertices colored with each color j, 1 ≤ j ≤ i -1. In this paper we give bounds for the Grundy number of some graphs and cartesian products of graphs. In particular, we determine an exact value of this parameter for n-dimensional meshes and some n-dimensional toroidal meshes. Finally, we present an...

Guessing secrets.

Chung, Fan, Graham, Ronald, Leighton, Tom (2001)

The Electronic Journal of Combinatorics [electronic only]

H -convex graphs

Gary Chartrand, Ping Zhang (2001)

Mathematica Bohemica

For two vertices u and v in a connected graph G , the set I ( u , v ) consists of all those vertices lying on a u - v geodesic in G . For a set S of vertices of G , the union of all sets I ( u , v ) for u , v S is denoted by I ( S ) . A set S is convex if I ( S ) = S . The convexity number c o n ( G ) is the maximum cardinality of a proper convex set in G . A convex set S is maximum if | S | = c o n ( G ) . The cardinality of a maximum convex set in a graph G is the convexity number of G . For a nontrivial connected graph H , a connected graph G is an H -convex graph if G contains...

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