We investigate the computational complexity of several decision problems in hedonic coalition formation games and demonstrate that attaining stability in such games remains NP-hard even when they are additive. Precisely, we prove that when either core stability or strict core stability is under consideration, the existence problem of a stable coalition structure is NP-hard in the strong sense. ...

The coalition structure generation problem represents an active research area in multi-agent systems. A coalition structure is defined as a partition of the agents involved in a system into disjoint coalitions. The problem of finding the optimal coalition structure is NP-complete. In order to find the optimal solution in a combinatorial optimization problem it is theoretically possible to enume...

A graph is an opposition graph, respectively, a coalition graph, if it admits an acyclic orientation which puts the two end-edges of every chordless 4-vertex path in opposition, respectively, in the same direction. Opposition and coalition graphs have been introduced and investigated in connection to perfect graphs. Recognizing and characterizing opposition and coalition graphs still remain lon...

Unanimity and monotonicity are natural assumptions in most cases. Unanimity reflects the fact that all agents agree; hence, the coalition should be winning. Monotonicity tells that the addition of agents in the coalition cannot turn a winning coalition into a losing one, which is reasonable for voting: more supporters should not harm the coalition. A first way to represent a voting game is by l...

The purpose of this study is to examine how language affects coalition formation in multiparty negotiations. The authors relied on communication accommodation theory for theoretical framing and hypothesized that language can help coalition partners reach an agreement when it is used to increase a sense of unity. Findings of an experimental study support this hypothesis, demonstrating that great...

Our concern is the extension of the theory of the Shapley value to problems involving externalities. Using the standard axiom systems behind the Shapley value for an arbitrary exogenous coalition structure leads to the identification of bounds on players’ payoffs around an “externality-free” value. In endogenizing the coalition structure, we analyze a two-stage process of coalition formation in...

We introduce a new variant of hedonic coalition formation games in which agents have two levels of preference on their own coalitions: preference on the set of “roles” that makes up the coalition, and preference on their own role within the coalition. We define several stability notions and optimization problems for this model. We prove the hardness of the decision problems related to our optim...

The opinions expressed in this paper do not necessarily reflect the position of Summary We investigate the computational complexity of several decision problems in hedonic coalition formation games and demonstrate that attaining stability in such games remains NP-hard even when they are additive. Precisely, we prove that when either core stability or strict core stability is under consideration...

We study coalitional games where the proceeds from cooperation depend on the entire coalition structure. The coalition structure core (Kóczy, 2007) is a generalisation of the coalition structure core for such games. We introduce a noncooperative, sequential coalition formation model and show that the set of equilibrium outcomes coincides with the recursive core. In order to extend past results ...

Carpal coalition is a rare asymptomatic condition and usually detected incidentally. It may be symptomatic after a trauma and causes pain on the medial part of the wrist. Most often, lunotriquetral coalition is seen. The second frequent one is capitate-hamate coalition. It can be seen as an isolated entity or as a part of a congenital anomaly. Four radiological sub-types have been determined. I...