Game theory
John Nash proved that games with several players have a stable solution provided that coalitions between players are disallowed. Nash won the Nobel Prize for economics for this important result which extended von Neumann's theory of zero-sum games. Nash's stable solution is known as the Nash equilibrium.
If cooperation between players is allowed, then the game becomes more complex; many concepts have been developed to analyze such games. Cooperative game theory uses coalition formation, joint actions, and payoffs for analysis.
