Michel Le Breton

Equivalence of strong and coalition-proof Nash equilibria in games without spillovers (*)

This paper examines the conditions which guarantee that the set of coalition-proof Nash equilibria coincides with the set of strong Nash equilibria in the normal form games without spillovers. We find that population monotonicity properties of the payoff functions, when the payoff of a player changes monotonically when the size of the group of players choosing the same strategy increases, are crucial to obtain the equivalence of these two solution concepts. We identify the classes of games, satisfying population monotonicity properties, which yield the equivalence of the set of coalition-proof Nash equilibria and the set of strong Nash equilibria. We also provide sufficient conditions for the equivalence result even when the population monotonicity assumptions are relaxed.

Equivalence of Strong and Coalition-Proof Nash Equilibria in Games without Spillovers

SummaryThis paper examines the conditions which guarantee that the set of coalition-proof Nash equilibria coincides with the set of strong Nash equilibria in the normal form games withoutspillovers. We find thatpopulation monotonicity properties of the payoff functions, when the payoff of a player changes monotonically when the size of the group of players choosing the same strategy increases, are crucial to obtain the equivalence of these two solution concepts. We identify the classes of games, satisfying population monotonicity properties, which yield the equivalence of the set of coalition-proof Nash equilibria and the set of strong Nash equilibria. We also provide sufficient conditions for the equivalence result even when the population monotonicity assumptions are relaxed.

On existence of undominated pure strategy Nash equilibria in anonymous nonatomic games

Abstract We strengthen the theorem of Schmeidler (1973) on the existence of a pure strategy Nash equilibrium in anonymous games with a continuum of players by showing the nonemptiness of the Pareto frontier of the set of pure strategy Nash equilibria.