Narrow Results

In this paper, we study the impact of countries’ subjective beliefs, i.e., pessimism and optimism, on international agreements to provide global public goods. Under symmetric beliefs, we find that while pessimism (optimism) could decrease (increase) signatories’ efforts, it can also increase (decrease) the coalition size. Under asymmetric beliefs, optimists entering the coalition may crowd out the more pessimistic countries. If a stable coalition exists, then while optimists are willing to participate even at rather small coalition sizes, the participation of more pessimistic types requires the coalition size to be larger. A stable coalition would consist of the most optimists and possibly some other types.

The deployment of fog computing has not only helped in task offloading for the end-users toward delay-sensitive task provisioning but also reduced the burden for cloud back-end systems to process variable workloads arriving from the user equipment. However, due to the constraints on the resources and computational capabilities of the fog nodes, processing the computational-intensive task within the defined timelines is highly challenging. Also, in this scenario, offloading tasks to the cloud creates a burden on the upload link, resulting in high resource costs and delays in task processing. Existing research studies have considerably attempted to handle the task allocation problem in fog–cloud networks, but the majority of the methods are found to be computationally expensive and incur high resource costs with execution time constraints. The proposed work aims to balance resource costs and time complexity by exploring collaboration among host machines over fog nodes. It introduces the concept of task scheduling and optimal resource allocation using coalition formation methods of game theory and pay-off computation. The work also encourages the formation of coalitions among host machines to handle variable traffic efficiently. Experimental results show that the proposed approach for task scheduling and optimal resource allocation in fog computing outperforms the existing system by 56.71% in task processing time, 47.56% in unused computing resources, 8.33% in resource cost, and 37.2% in unused storage.

A model of coalition government formation is presented in which inefficient, non-minimal winning coalitions may form in Nash equilibrium. Predictions for five games are presented and tested experimentally. The experimental data support potential maximization as a refinement of Nash equilibrium. In particular, the data support the prediction that non-minimal winning coalitions occur when the distance between policy positions of the parties is small relative to the value of forming the government. These conditions hold in games 1, 3, 4 and 5, where subjects played their unique potential-maximizing strategies 91, 52, 82 and 84 percent of the time, respectively. In the remaining game (Game 2) experimental data support the prediction of a minimal winning coalition. Players A and B played their unique potential-maximizing strategies 84 and 86 percent of the time, respectively, and the predicted minimal-winning government formed 92 percent of the time (all strategy choices for player C conform with potential maximization in Game 2). In Games 1, 2, 4 and 5 over 98 percent of the observed Nash equilibrium outcomes were those predicted by potential maximization. Other solution concepts including iterated elimination of weakly dominated strategies and strong/coalition-proof Nash equilibrium are also tested.

This paper establishes sufficient conditions for the existence of a stable coalition structure in the "coalition unanimity" game of coalition formation, first defined by Hart and Kurz (1983) and more recently studied by Yi (1997, 2003). Our conditions are defined on the strategic form game used to derive the payoffs of the game of coalition formation. We show that if no synergies are generated by the formation of coalitions, a stable coalition structure always exists provided that players are symmetric and either the game exhibits strategic complementarity or, if strategies are substitutes, the best reply functions are contractions.

In this paper we give an overview of various methods used to study cooperation within a set of players. Besides the classical games with transferable utility and games without transferable utility, recently new models have been proposed: the coalition formation games. In these, each player has his own preferences over coalitions to which he could belong and the quality of a coalition structure is evaluated according to its stability. We review various definitions of stability and restrictions of preferences ensuring the existence of a partition stable with respect to a particular stability definition. Further, we stress the importance of preferences over sets of players derived from preferences over individuals and review the known algorithmic results for special types of preferences derived from the best and/or the worst player of a coalition.

We propose an abstract approach to coalition formation that focuses on simple merge and split rules transforming partitions of a group of players. We identify conditions under which every iteration of these rules yields a unique partition. The main conceptual tool is a specific notion of a stable partition. The results are parametrized by a preference relation between partitions of a group of players and naturally apply to coalitional TU-games, hedonic games and exchange economy games.

This paper reviews the game-theoretic literature on collaborative environmental management. It begins with a survey of static models of international environmental agreements (IEAs), comparing their underlying assumptions and their results. Extensions of the basic model to allow for both adaptation and mitigation, and for transfer payments are considered. We review the various concepts of coalitional stability, such as internal and external stability and far-sighted stability in the noncooperative strand, and the gamma core concept in the cooperative strand. The network approach to cooperation building is reviewed. We next survey extensions of IEA theory to dynamic models with stock pollutants, allowing membership status to change over time. Finally, dynamic cooperative games of pollution with transfer payments that take place over time are discussed.

In this paper, we examine whether farsighted players form the efficient grand coalition structure in coalition formation games. We propose a stability concept for a coalition structure, called sequentially stability, when only bilateral mergers of two separate coalitions are feasible because of high negotiation costs. We provide an algorithm to check the sequential stability of the grand coalition structure as well as sufficient conditions for which the efficient grand coalition structure is sequentially stable. We also illustrate out results by means of common pool resource games and Cournot oligopoly games.

A party is dominant if there is a majority coalition to which that party belongs such that it affords this party more possibilities to form an alternative winning coalition than any of the other members of the coalition. I present empirical evidence showing that an allocation of seats in a parliament is biased toward the high frequency occurrence of a dominant party and the low frequency occurrence of a dictator. If a dominant party forms a cabinet coalition, and if that cabinet coalition has a majority in parliament, then the dominant party tends to form a coalition which it dominates.

The partition function approach is applied to study coalition formation in the Northeast Atlantic mackerel fishery in the presence of externalities. Atlantic mackerel is mainly exploited by the European Union (EU), the United Kingdom (UK), Norway, the Faroe Islands and Iceland. Two games are considered. First, a four-player game where the UK is still a member of the EU. Second, a five-player game where the UK is no longer a member of the union. Each game is modeled in two stages. In the first stage, players form coalitions following a predefined set of rules. In the second stage, given the coalition structure that has been formed, each coalition chooses the economic strategy that maximizes its own net present value of the fishery, given the behavior of the other coalitions. The game is solved using backward induction to obtain the set of Nash equilibria coalition structures in pure strategies, if any. We find that the current management regime is among the stable coalition structures in all eight scenarios of the four-player game but in only one case of the five-player game. In addition, stability in the five-player game is sensitive to the growth function applied and the magnitude of the stock elasticity parameter.

Despite the fact that social networks are ubiquitous on the Internet, only few websites exploit the potential of combining user communities and online marketplaces. Not many platforms allow users to engage in a phenomenon called "group buying" — buyers joining groups, or coalitions, to bundle their purchasing power towards sellers. We argue that this may be due to a lack of face-to-face interaction on the Internet; often, users do not know which other users to trust, which makes them suspicious of engaging in online business, in particular if many unknown other parties are involved. This situation, however, can be alleviated by leveraging the social networks of users: based on who a user knows and is connected to, a trust metric — for example, the TrustWebRank metric developed by us — can be computed to assess who else may be considered trustworthy to that user. In this paper, we build a simple agent-based model of coalition formation among agents in the setting of group buying in an electronic marketplace. In this model, agents use their trust relationships in order to determine who to form coalitions with. We show that this leads agents to experience high utility and that agents are able to learn who is trustworthy and who is not, even when they have no initial knowledge about the trustworthiness of other agents. This work may provide the foundation for a real-world application of an online coalition formation platform for e-commerce built on a social networking platform such as Facebook.

Optimal task allocation among the suitably formed robot groups is one of the key issues to be investigated for the smooth operations of multi-robot systems. Considering the complete execution of available tasks, the problem of assigning available resources (robot features) to the tasks is computationally complex, which may further increase if the number of tasks increases. Popularly this problem is known as multi-robot coalition formation (MRCF) problem. Genetic algorithms (GAs) have been found to be quite efficient in solving such complex computational problems. There are several GA-based approaches to solve MRCF problems but none of them have considered the dynamic GA variants. This paper considers immigrants-based GAs viz. random immigrants genetic algorithm (RIGA) and elitism based immigrants genetic algorithm (EIGA) for optimal task allocation in MRCF problem. Further, it reports a novel use of these algorithms making them adaptive with certain modifications in their traditional attributes by adaptively choosing the parameters of genetic operators and terms them as adaptive RIGA (aRIGA) and adaptive EIGA (aEIGA). Extensive simulation experiments are conducted for a comparative performance evaluation with respect to standard genetic algorithm (SGA) using three popular performance metrics. A statistical analysis with the analysis of variance has also been performed. It is demonstrated that RIGA and EIGA produce better solutions than SGA for both fixed and adaptive genetic operators. Among them, EIGA and aEIGA outperform RIGA and aRIGA, respectively.

This paper investigates which drivers affect the formation and stability of international climate agreements (ICAs). The applied model STACO is used to project costs and benefits of an international agreement on climate change mitigation activities. The simulation results show that an incentive-based permit allocation scheme is an essential driver in stabilizing larger coalitions. Regional damage shares turn out to be another driver of coalition formation but global damages do not seem to be, thus illustrating that international coalition formation is a matter of relative costs and benefits across regions. No allocation scheme can, however, assure the stability of a global agreement due to huge free-rider incentives. This requires alternative rules, such as a condition that some players are essential in a coalition, or accepting a small loss from cooperation.

We investigate whether global cooperation on emissions abatement can be improved if asymmetric countries agree to sign one out of several environmental agreements. The analysis is based on a two-stage game theoretical model. Conditions for stable coalitions and the resulting global emissions are determined. We allow for multiple coalitions with all countries being different, and analyze the effects in the cases of increasing marginal damages from emissions and of decreasing marginal benefits of emissions. We find that in the case of decreasing marginal benefits and constant marginal damages, admitting multiple coalitions increases the number of cooperating countries and reduces emissions (compared to the standard case with a single coalition). For increasing marginal damages and constant marginal benefits, however, multiple stable coalitions cannot coexist. If both damages and benefits are nonlinear, admitting multiple coalitions can decrease emissions. The paper thus contributes to the emerging discussion on the scope and limits of climate clubs.

The partition function approach is applied to study coalition formation in the Northeast Atlantic mackerel fishery in the presence of externalities. Atlantic mackerel is mainly exploited by the European Union (EU), the United Kingdom (UK), Norway, the Faroe Islands and Iceland. Two games are considered. First, a four-player game where the UK is still a member of the EU. Second, a five-player game where the UK is no longer a member of the union. Each game is modeled in two stages. In the first stage, players form coalitions following a predefined set of rules. In the second stage, given the coalition structure that has been formed, each coalition chooses the economic strategy that maximizes its own net present value of the fishery, given the behavior of the other coalitions. The game is solved using backward induction to obtain the set of Nash equilibria coalition structures in pure strategies, if any. We find that the current management regime is among the stable coalition structures in all eight scenarios of the four-player game but in only one case of the five-player game. In addition, stability in the five-player game is sensitive to the growth function applied and the magnitude of the stock elasticity parameter.

Task execution in a multi-agent, multi-task environment often requires allocation of agents to different tasks and cooperation among agents. Agents usually have limited resources that cannot be regenerated, and are heterogeneous in capabilities and available resources. Agent coalition benefits the system because agents can complement each other by taking different functions and hence improve the performance of a task. Good task allocation decision in a dynamic and unpredictable environment must consider overall system optimization across tasks, and the sustainability of the agent society for the future tasks and usage of the resources. In this chapter we present an efficient scheme to solve the real time team/coalition formation problem. Our domain of applications is coalition formation of various Unmanned Aerial Vehicles (UAVs) for cooperative sensing and attack. In this scheme each agent bids the maximum affordable cost for each task. Based on the bidding information and the cost curves of the tasks, the agents are split into groups, one for each task, and cost division among the group members for each task is calculated. This cost sharing scheme provably guarantees the stability in cost division within each coalition in terms of the core in game theory, therefore achieves good sustainability of the agent society with balanced resource depletions across agents. Simulation results show that, under most conditions, our scheme greatly increases the total utility of the system compared with the traditional heuristics.