Canadians also strong in alliances

Strong Alliances in Graphs

For any simple connected graph $G=(V,E)$, a defensive alliance is a subset $S$ of $V$ satisfying the condition that every vertex $vin S$ has at most one more neighbour in $V-S$ than it has in $S$. The minimum cardinality of any defensive alliance in $G$ is called the alliance number of $G$, denoted $a(G)$. In this paper, we introduce a new type of alliance number called $k$-strong alliance numb...

On global (strong) defensive alliances in some product graphs

A defensive alliance in a graph is a set $S$ of vertices with the property that every vertex in $S$ has at most one moreneighbor outside of $S$ than it has inside of $S$. A defensive alliance $S$ is called global if it forms a dominating set. The global defensive alliance number of a graph $G$ is the minimum cardinality of a global defensive alliance in $G$. In this article we study the global ...

On defensive alliances and strong global offensive alliances

We consider complexity issues and upper bounds for defensive alliances and strong global offensive alliances in graphs. We prove that it is NP-complete to decide for a given 6-regular graph G and a given integer a, whether G contains a defensive alliance of order at most a. Furthermore, we prove that determining the strong global offensive alliance number γô(G) of a graph G is APX-hard for cubi...

Healthy Canadians in 2010?

Vanishing Canadians.

Take a look around at your fellow Canadians, because they are slowly disappearing. All of the scenarios projected by Statistics Canada about population growth in Canada over the next 50 years show a “negative increase” (you’ve got to love bureaucratic language) in the number of births minus deaths.1 In the low-growth scenario for the Canadian population, the first year in which there will be mo...