Emiko Fukuda

Theoretical and experimental investigations of the performance of keyword auction mechanisms

Two keyword auction mechanisms, the Generalized Second-Price auction (GSP) and the Vickrey-Clarke-Groves mechanism (VCG), were compared theoretically and experimentally. The former is widely used in practice; the latter is not, but it has a dominant strategy equilibrium where all participants bid their true values. In the theoretical investigation, by applying the �locally envy-free Nash equilibrium� to the VCG, we found that the allocations are efficient and that upper and lower bounds of the auctioneers revenue coincide in the two mechanisms. A laboratory experiment, in which the revenues and efficiencies were similar in both mechanisms, supported this result

GENERALIZED CORES AND STABLE SETS FOR FUZZY GAMES

Core elements (a la Aubin) of a fuzzy game can be associated with additive separable supporting functions of fuzzy games. Generalized cores whose elements consist of more general separable supporting functions of the game are introduced and studied. While the Aubin core of unanimity games can be empty, the generalized core of unanimity games is nonempty. Properties of the generalized cores and their relations to stable sets are studied. For convex fuzzy games interesting properties are found such as the fact that the generalized core is a unique generalized stable set.

Fuzzy clan games and bi-monotonic allocation rules

In this paper the class of fuzzy clan games is introduced. The cores of such games have an interesting shape which inspires to define a class of compensation-sharing rules that are additive and stable on the cone of fuzzy clan games. Further, the notion of bi-monotonic participation allocation scheme (bi-pamas) is introduced and it turns out that each core element of a fuzzy clan game is extendable to a bi-pamas.

A wareness, belief, and communication reaching consensus

This article studies graph-theoretical conditions under which communication will lead to consensus among players about their decisions in circumstances where there are more than tow players and they interact in pair without public announcement. It is shown that comsensus on their decisions can be guaranteed if the communication graph contains no cycle. Where none of the requirements for players knowledge is imposed as in the standard model of knowledg with partitional information structure.

Risk evaluation and games in mine warfare considering shipcounter effects

Abstract Mines are believed to have suitable cost performance because cheap weapons prevent opponents from freely engaging in activity in mined areas for a comparatively long time. Mine warfare (MW) can be regarded as combat between a minefield planner and mine countermeasure (MCM) forces. The minefield planner equips influence mines with mine counter-countermeasures (MCCMs), which increase the difficulty of their removal. One of the MCCMs is a mine shipcounter, which provides a mine detonation fuse that triggers with some delay after the mine sensor detects vessels. In this paper, we develop a mathematical model of the MCM operation against scattered naval mines with shipcounters and analyze MW as a two-sided warfare game between the minefield planner and the MCM forces. The MCM forces must make a clever choice between mine-hunting or sweeping operations because, depending on the MCM operations, the shipcount has different effects on the removal of mines or on the damage risk to civilian ships transiting in a channel. First, we evaluate the performances of hunting and sweeping considering the mine shipcount; second, we consider a simple game with the minefield planner and the MCM forces as players and analyze rational strategies for these decision makers in MW.

Compromising In Partition Function Form Games And Cooperation In Perfect Extensive Form Games

In this paper reasonable payoff intervals for players in a game in partition function form (p.f.f. game) are introduced and used to define the notion of compromisable p.f.f. game. For a compromisable p.f.f. game a compromise value is defined for which an axiomatic characterization is provided. Also a generic subclass of games in extensive form of perfect information without chance moves is introduced. For this class of perfect extensive form games there is a natural credible way to define a p.f.f. game if the players consider cooperation. It turns out that the p.f.f. games obtained in this way are compromisable.