Nash equilibrium: a standalone construct

John Nash introduced the equilibrium point in Equilibrium Points in n-Person Games (1950) and gave the fuller treatment in Non-Cooperative Games (1951): a Nash equilibrium is a choice of strategy by every player at once such that no single player can raise their own payoff by switching strategy while the others keep theirs fixed. In plain terms, each player is already doing the best they can given what everyone else is doing, so no one has a private reason to move. Nash proved that every finite game has at least one such equilibrium once players are allowed to mix, meaning to randomise over their available actions with fixed probabilities. The construct is a landmark because it defines stability for interdependent decisions of any kind, from pricing and bargaining to voting and evolutionary biology, wherever the best action for one party depends on the actions of others, and it earned Nash a share of the 1994 Nobel Memorial Prize in Economic Sciences.[1][2]

Unit

A strategy profile, one strategy per player, from which no player can profitably deviate alone

Recovery means

Not applicable

Measured by

Identified as a fixed point of the best-response map, shown to exist by the Kakutani and Brouwer fixed-point theorems