Computing the molecular expansion of species with the Maple package Devmol.
A dominating set in a graph is a connected dominating set of if it induces a connected subgraph of . The connected domatic number of is the maximum number of pairwise disjoint, connected dominating sets in . We establish a sharp lower bound on the number of edges in a connected graph with a given order and given connected domatic number. We also show that a planar graph has connected domatic number at most 4 and give a characterization of planar graphs having connected domatic number 3.
The intersection graph of a graph has for vertices all the induced paths of order 3 in . Two vertices in are adjacent if the corresponding paths in are not disjoint. A -container between two different vertices and in a graph is a set of internally vertex disjoint paths between and . The length of a container is the length of the longest path in it. The -wide diameter of is the minimum number such that there is a -container of length at most between any pair of different...
In [1] Burger and Mynhardt introduced the idea of universal fixers. Let G = (V, E) be a graph with n vertices and G’ a copy of G. For a bijective function π: V(G) → V(G’), define the prism πG of G as follows: V(πG) = V(G) ∪ V(G’) and , where . Let γ(G) be the domination number of G. If γ(πG) = γ(G) for any bijective function π, then G is called a universal fixer. In [9] it is conjectured that the only universal fixers are the edgeless graphs K̅ₙ. In this work we generalize the concept of universal...