Coalitional stability in structured environments

In many real-world settings, the structure of the environment constrains the formation of coalitions among agents. Therefore, examining the stability of formed coalition structures in such settings is of natural interest. We address this by considering core-stability within various models of cooperative games with structure. First, we focus on characteristic function games defined on graphs that determine feasible coalitions. In particular, a coalition S can emerge only if S is a connected set in the graph. We study the (now modified) core, in which it suffices to check only feasible deviations. Specifically, we investigate core non-emptiness as well as the complexity of computing stable configurations. We then move on to the more general class of (graph-restricted) partition function games, where the value of a coalition depends on which other coalitions are present, and provide the first stability results in this domain. Finally, we propose a Bayesian extension of partition function games, in which information regarding the success of a deviation is provided in the form of a probability distribution describing the possible reactions of non-deviating agents, and provide the first core-stability results in this model also. Copyright © 2012, International Foundation for Autonomous Agents and Multiagent Systems (www.ifaamas.org). All rights reserved