Equilibrium Departures from Common Knowledge in Games with Non-Additive Expected Utility

This paper concerns the interpretation of equilibrium in non-additive beliefs in two-player normal form games. We argue that such equilibria involve beliefs and actions which are consistent with a lack of common knowledge of the game. Our argument rests on representation results which show that different notions of equilibrium in games with non-additive beliefs may be reinterpreted as equilibrium in associated games of incomplete information with additive (Bayesian) beliefs where common knowledge of the (original) game does not apply. The representation results show one way of comparing and understanding the various notions of equilibrium, for games with non-additive beliefs, advanced in the literature.