The pure Nash equilibrium property and the quasi-acyclic condition

This paper presents a sufficient condition for the quasi-acyclic condition. A game is quasi-acyclic if from any strategy profile, there exists a finite sequence of strict best replies that ends in a pure strategy Nash equilibrium. The best-reply dynamics must converge to a pure strategy Nash equilibrium in any quasi-acyclic game. A game has the pure Nash equilibrium property (PNEP) if there is a pure strategy Nash equilibrium in any game constructed by restricting the set of strategies to a subset of the set of strategies in the original game. Any finite, ordinal potential game and any finite, supermodular game have the PNEP. We show that any finite, two-player game with the PNEP is quasi-acyclic.best-reply dynamics

Monotone and local potential maximizers in symmetric 3x3 supermodular games

Generalized notions of potential maximizer, monotone potential maximizer (MP-maximizer) and local potential maximizer (LP-maximizer), are studied. It is known that 2x2 coordination games generically have a potential maximizer, while symmetric 4x4 supermodular games may have no MP- or LP-maximizer. This note considers the case inbetween, namely the class of (generic) symmetric 3x3 supermodular coordination games. This class of games are shown to always have a unique MP-maximizer, and its complete characterization is given. A nondegenerate example demonstrates that own-action quasiconcave supermodular games may have more than one LP-maximizers.equilibrium selection, supermodular game, monotone potential, MP-maximizer, local potential, LP-maximizer

Robustness to incomplete information in repeated games

This paper extends the framework of Kajii and Morris (1997) to study the question of robustness to incomplete information in repeated games. We show that dynamically robust equilibria can be characterized using a one-shot robustness principle that extends the one-shot deviation principle. Using this result, we compute explicitly the set of dynamically robust equilibrium values in the repeated prisoners' dilemma. We show that robustness requirements have sharp intuitive implications regarding when cooperation can be sustained, what strategies are best suited to sustain cooperation, and how changes in payoffs affect the sustainability of cooperation. We also show that a folk theorem in dynamically robust equilibria holds, but requires stronger identifiability conditions than the pairwise full rank condition of Fudenberg, Levine and Maskin (1994).Robustness to incomplete information, one-shot robustness principle, repeated Prisoners' Dilemma, selective punishment, folk theorem

Multi-sender cheap talk with restricted state spaces

This paper analyzes multi-sender cheap talk when the state space might be restricted, either because the policy space is restricted, or the set of rationalizable policies of the receiver is not the whole space. We provide a necessary and sufficient condition for the existence of a fully revealing perfect Bayesian equilibrium for any state space. We show that if biases are large enough and are not of similar directions, where the notion of similarity depends on the shape of the state space, then there is no fully revealing perfect Bayesian equilibrium. The results suggest that boundedness, as opposed to dimensionality, of the state space plays an important role in determining the qualitative implications of a cheap talk model. We also investigate equilibria that satisfy a robustness property, diagonal continuity.Cheap talk, two senders, multidimensional state space

Algebraic curves admitting the same Galois closure for two projections

A criterion for the existence of a plane model of an algebraic curve such that the Galois closures of projections from two points are the same is presented. As an application, it is proved that the Hermitian curve in positive characteristic coincides with the Galois closures of projections of some plane curve from some two non-uniform points.Comment: 6 page

Monotone methods for equilibrium selection under perfect foresight dynamics

This paper studies a dynamic adjustment process in a large society of forward-looking agents where payoffs are given by a normal form supermodular game. The stationary states of the dynamics correspond to the Nash equilibria of the stage game. It is shown that if the stage game has a monotone potential maximizer, then the corresponding stationary state is uniquely linearly absorbing and globally accessible for any small degree of friction. A simple example of a unanimity game with three players is provided where there are multiple globally accessible states for a small friction.Equilibrium selection, perfect foresight dynamics, supermodular game, strategic complementarity, stochastic dominance, potential, monotone potential