On Singleton Congestion Games with Resilience Against Collusion

We study the subclass of singleton congestion games in which there are identical resources with increasing cost functions. In this domain, we prove that there always exists an outcome that is resilient to weakly-improving deviations by singletons (i.e., the outcome is a Nash equilibrium), by the grand coalition (i.e., the outcome is Pareto efficient), and by coalitions with respect to an a priori given partition coalition structure (i.e., the outcome is a partition equilibrium). To our knowledge, this is the strongest existence guarantee in the literature on congestion games when weakly-improving deviations are considered. Our proof technique gives the false impression of a potential function argument but it is a novel application of proof by contradiction.