1,028 research outputs found
Matrix approach to consistency of the additive efficient normalization of semivalues
In fact the Shapley value is the unique efficient semivalue. This motivated Ruiz et al. to do additive efficient normalization for semivalues. In this paper, by matrix approach we derive the relationship between the additive efficient normalization of semivalues and the Shapley value. Based on the relationship, we axiomatize the additive efficient normalization of semivalues as the unique solution verifying covariance, symmetry, and reduced game property with respect to the reduced game
Matrix analysis for associated consistency in cooperative game theory
Hamiache's recent axiomatization of the well-known Shapley value for TU games states that the Shapley value is the unique solution verifying the following three axioms: the inessential game property, continuity and associated consistency. Driessen extended Hamiache's axiomatization to the enlarged class of efficient, symmetric, and linear values, of which the Shapley value is the most important representative.
In this paper, we introduce the notion of row (resp. column)-coalitional matrix in the framework of cooperative game theory. Particularly, both the Shapley value and the associated game are represented algebraically by their coalitional matrices called the Shapley standard matrix and the associated transformation matrix respectively. We develop a matrix approach for Hamiache's axiomatization of the Shapley value. The associated consistency for the Shapley value is formulated as the matrix equality The diagonalization procedure of and the inessential property for coalitional matrices are fundamental tools to prove the convergence of the sequence of repeated associated games as well as its limit game to be inessential. In addition, a similar matrix approach is applicable to study Driessen's axiomatization of a certain class of linear values. Matrix analysis is adopted throughout both the mathematical developments and the proofs. In summary, it is illustrated that matrix analysis is a new and powerful technique for research in the field of cooperative game theory
The Cost of Stability in Coalitional Games
A key question in cooperative game theory is that of coalitional stability,
usually captured by the notion of the \emph{core}--the set of outcomes such
that no subgroup of players has an incentive to deviate. However, some
coalitional games have empty cores, and any outcome in such a game is unstable.
In this paper, we investigate the possibility of stabilizing a coalitional
game by using external payments. We consider a scenario where an external
party, which is interested in having the players work together, offers a
supplemental payment to the grand coalition (or, more generally, a particular
coalition structure). This payment is conditional on players not deviating from
their coalition(s). The sum of this payment plus the actual gains of the
coalition(s) may then be divided among the agents so as to promote stability.
We define the \emph{cost of stability (CoS)} as the minimal external payment
that stabilizes the game.
We provide general bounds on the cost of stability in several classes of
games, and explore its algorithmic properties. To develop a better intuition
for the concepts we introduce, we provide a detailed algorithmic study of the
cost of stability in weighted voting games, a simple but expressive class of
games which can model decision-making in political bodies, and cooperation in
multiagent settings. Finally, we extend our model and results to games with
coalition structures.Comment: 20 pages; will be presented at SAGT'0
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
Cooperative Games with Overlapping Coalitions
In the usual models of cooperative game theory, the outcome of a coalition
formation process is either the grand coalition or a coalition structure that
consists of disjoint coalitions. However, in many domains where coalitions are
associated with tasks, an agent may be involved in executing more than one
task, and thus may distribute his resources among several coalitions. To tackle
such scenarios, we introduce a model for cooperative games with overlapping
coalitions--or overlapping coalition formation (OCF) games. We then explore the
issue of stability in this setting. In particular, we introduce a notion of the
core, which generalizes the corresponding notion in the traditional
(non-overlapping) scenario. Then, under some quite general conditions, we
characterize the elements of the core, and show that any element of the core
maximizes the social welfare. We also introduce a concept of balancedness for
overlapping coalitional games, and use it to characterize coalition structures
that can be extended to elements of the core. Finally, we generalize the notion
of convexity to our setting, and show that under some natural assumptions
convex games have a non-empty core. Moreover, we introduce two alternative
notions of stability in OCF that allow a wider range of deviations, and explore
the relationships among the corresponding definitions of the core, as well as
the classic (non-overlapping) core and the Aubin core. We illustrate the
general properties of the three cores, and also study them from a computational
perspective, thus obtaining additional insights into their fundamental
structure
Testing Core Membership in Public Goods Economies
This paper develops a recent line of economic theory seeking to understand
public goods economies using methods of topological analysis. Our first main
result is a very clean characterization of the economy's core (the standard
solution concept in public goods). Specifically, we prove that a point is in
the core iff it is Pareto efficient, individually rational, and the set of
points it dominates is path connected.
While this structural theorem has a few interesting implications in economic
theory, the main focus of the second part of this paper is on a particular
algorithmic application that demonstrates its utility. Since the 1960s,
economists have looked for an efficient computational process that decides
whether or not a given point is in the core. All known algorithms so far run in
exponential time (except in some artificially restricted settings). By heavily
exploiting our new structure, we propose a new algorithm for testing core
membership whose computational bottleneck is the solution of convex
optimization problems on the utility function governing the economy. It is
fairly natural to assume that convex optimization should be feasible, as it is
needed even for very basic economic computational tasks such as testing Pareto
efficiency. Nevertheless, even without this assumption, our work implies for
the first time that core membership can be efficiently tested on (e.g.) utility
functions that admit "nice" analytic expressions, or that appropriately defined
-approximate versions of the problem are tractable (by using
modern black-box -approximate convex optimization algorithms).Comment: To appear in ICALP 201
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