A global defensive (respectively, offensive) alliance in a graph G = (V,E) is a set of vertices S ⊆ V with the properties that every vertex in V − S has at least one neighbor in S, and for each vertex v in S (respectively, in V − S) at least half the vertices from the closed neighborhood of v are in S. These alliances are called strong if a strict majority of vertices from the closed neighborho...

A defensive (offensive) k-alliance in Γ = (V,E) is a set S ⊆ V such that for every v ∈ S (v ∈ ∂S), the number of neighbors v has in S is at least k more than the number of neighbors it has in V \ S. A set X ⊆ V is defensive (offensive) k-alliance free, if for all defensive (offensive) k-alliance S, S \ X 6= ∅, i.e., X do not contain any defensive (offensive) k-alliance as a subset. A set Y ⊆ V ...

A set S of vertices of a graph is a defensive alliance if, for each element of S, the majority of its neighbors is in S. The problem of finding a defensive alliance of minimum size in a given graph is NP-hard and there are polynomial-time algorithms if certain parameters are bounded by a fixed constant. In particular, fixed-parameter tractability results have been obtained for some structural p...

A global boundary defensive k-alliance in a graph G = (V,E) is a dominating set S of vertices of G with the property that every vertex in S has k more neighbors in S than it has outside of S. A global boundary offensive k-alliance in a graph G is a set S of vertices of G with the property that every vertex in V − S has k more neighbors in S than it has outside of S. We define a global boundary ...

States form defensive military alliances to enhance their security in the face of potential or realized interstate conflict. The network of these international alliances is increasingly interconnected, now linking most of the states in a complex web of ties. These alliances can be used both as a tool for securing cooperation and to foster peace between direct partners. However, do indirect conn...

Simple combinations of common competitive mechanisms can easily result in cyclic competitive dominance relationships between species. The topological features of such competitive networks allow for complex spatial coexistence patterns. We investigate self-organization and coexistence in a lattice model, describing the spatial population dynamics of competing bacterial strains. With increasing d...

Creating effective strategic alliance is a useful method for the global expansion of international companies and managing strategic alliances is an important research project to the success of strategic alliances. This paper focuses on the practical problems of strategic alliances in China and explores how to manage such alliances. This research aims to introduce the basic background of strateg...

I examine how firms use alliances to respond to the alliance networks of their rivals, by either allying with their rivals’ partners or by building countervailing alliances. Evidence from the global airline industry (1994–98) suggests that these strategic responses depend on alliance cospecialization. Cospecialized alliances by rivals may involve exclusivity, precluding alliances with the rival...