AGM-consistency and perfect Bayesian equilibrium. Part II: from PBE to sequential equilibrium.

This is a slightly extended version of a chapter prepared for the Handbook of Logics for Knowledge and Belief edited by Hans van Ditmarsch, Joseph Y. Halpern, Wiebe van der Hoek, and Barteld Kooi, College Publications, London. In [5] (Int. J. Game Theory, 42:567-592, 2013) a general notion of perfect Bayesian equilib- rium (PBE) was introduced for extensive-form games and shown to be intermediate between subgame-perfect equilibrium and sequential equilibrium. The essential ingredient of the pro- posed notion is the existence of a plausibility order on the set of histories that rationalizes a given assessment. In this paper we study restrictions on the belief revision policy encoded in a plausibility order and provide necessary and su¢ cient conditions for a PBE to be a sequential equilibrium.