The NTU consistent coalitional value

We introduce a new value for NTU games with coalition structure. This value coincides with the consistent value for trivial coalition structures, and with the Owen value for TU games with coalition structure. Furthermore, we present two characterizations: the first one using a consistency property and the second one using balanced contributions properties.consistent coalition structure value NTU balanced contributions

Farsighted Coalitional Stability in TU-games

We study farsighted coalitional stability in the context of TUgames. Chwe (1994, p.318) notes that, in this context, it is difficult to prove nonemptiness of the largest consistent set. We show that every TU-game has a nonempty largest consistent set. Moreover, the proof of this result points out that each TU-game has a farsighted stable set. We go further by providing a characterization of the collection of farsighted stable sets in TU-games. We also show that the farsighted core of a TU-game is empty or is equal to the set of imputations of the game. Next, the relationships between the core and the largest consistent set are studied in superadditive TU-games and in clan games. In the last section, we explore the stability of the Shapley value. It is proved that the Shapley value of a superadditive TU-game is always a stable imputation: it is a core imputation or it constitutes a farsighted stable set. A necessary and sufficient condition for a superadditive TU-game to have the Shapley value in the largest consistent set is given.

Efficient computation of the Shapley value for game-theoretic network centrality

The Shapley value—probably the most important normative payoff division scheme in coalitional games—has recently been advocated as a useful measure of centrality in networks. However, although this approach has a variety of real-world applications (including social and organisational networks, biological networks and communication networks), its computational properties have not been widely studied. To date, the only practicable approach to compute Shapley value-based centrality has been via Monte Carlo simulations which are computationally expensive and not guaranteed to give an exact answer. Against this background, this paper presents the first study of the computational aspects of the Shapley value for network centralities. Specifically, we develop exact analytical formulae for Shapley value-based centrality in both weighted and unweighted networks and develop efficient (polynomial time) and exact algorithms based on them. We empirically evaluate these algorithms on two real-life examples (an infrastructure network representing the topology of the Western States Power Grid and a collaboration network from the field of astrophysics) and demonstrate that they deliver significant speedups over the Monte Carlo approach. Fo

Learning Cooperative Games

This paper explores a PAC (probably approximately correct) learning model in cooperative games. Specifically, we are given $m$ random samples of coalitions and their values, taken from some unknown cooperative game; can we predict the values of unseen coalitions? We study the PAC learnability of several well-known classes of cooperative games, such as network flow games, threshold task games, and induced subgraph games. We also establish a novel connection between PAC learnability and core stability: for games that are efficiently learnable, it is possible to find payoff divisions that are likely to be stable using a polynomial number of samples.Comment: accepted to IJCAI 201

A bargaining approach to the consistent value for NTU games with coalition structure

The mechanism by Hart and Mas-Colell (1996) for NTU games is generalized so that a coalition structure among players is taken into account. The new mechanism yields the Owen value for TU games with coalition structure as well as the consistent value (Maschler and Owen 1989, 1992) for NTU games with trivial coalition structure. Furthermore, we obtain a solution for pure bargaining problems with coalition structure which generalizes the Nash (1950) bargaining solution.NTU consistent bargaining stationary subgame perfect equilibrium

Farsighted Stable Sets

A coalition is usually called stable if nobody has an immediate incentive to leave or to enter the coalition since he does not improve his payoff. This myopic behaviour does not consider further deviations which can take place after the first move. Chwe (1994) incorporated the idea of a farsighted behaviour in his definition of large consistent set (LCS). In some respects, we propose a different idea of dominance relation based on indirect dominance and on a different concept of belief on moving coalitions' behavior. A notion of stability for a coalitional game is introduced by taking into account the different degree of risk/safety of any player participating in a move. Some results about uncovered sets, internal stability are investigated. By exploiting our dominance and stability concepts, the prisoner's dilemma in coalitional form and its Nash equilibrium are studied. Some examples illustrating the differences between the largest consistent set, our stable set and stable set due to von Neumann and Morgenstern (1947) are presented.

One-deviation principle in coalition formation

We study coalitional one-deviation principle in a framework a la Chwe (1994). The principle requires that an active coalition or any of its subcoalition will not benefit from a single deviation to a strategy that specifies, for each history of coalitional moves, an active coalition and its move. A strategy meeting the one-deviation property is characterized. Moreover, it is shown to exist. Finally, the results are compared to the existing theories of coalitional games.one-deviation principle, coalition formation

Model checking coalitional games in shortage resource scenarios

Verification of multi-agents systems (MAS) has been recently studied taking into account the need of expressing resource bounds. Several logics for specifying properties of MAS have been presented in quite a variety of scenarios with bounded resources. In this paper, we study a different formalism, called Priced Resource-Bounded Alternating-time Temporal Logic (PRBATL), whose main novelty consists in moving the notion of resources from a syntactic level (part of the formula) to a semantic one (part of the model). This allows us to track the evolution of the resource availability along the computations and provides us with a formalisms capable to model a number of real-world scenarios. Two relevant aspects are the notion of global availability of the resources on the market, that are shared by the agents, and the notion of price of resources, depending on their availability. In a previous work of ours, an initial step towards this new formalism was introduced, along with an EXPTIME algorithm for the model checking problem. In this paper we better analyze the features of the proposed formalism, also in comparison with previous approaches. The main technical contribution is the proof of the EXPTIME-hardness of the the model checking problem for PRBATL, based on a reduction from the acceptance problem for Linearly-Bounded Alternating Turing Machines. In particular, since the problem has multiple parameters, we show two fixed-parameter reductions.Comment: In Proceedings GandALF 2013, arXiv:1307.416