A Homeomorphism Theorem for the Universal Type Space with the Uniform Weak Topology

Abstract

Kolmogorov’s extension theorem provides a natural mapping from the space of coherent hierarchies of an agent’s first-order, second-order, etc. beliefs to the space of probability measures over the exogenous parameters and the other agents' belief hierarchies. Mertens and Zamir (1985) showed that, if the spaces of belief hierarchies are endowed with the product topology, then this mapping is a homeomorphism. This paper shows that this mapping is also a homeomorphism if the spaces of belief hierarchies are endowed with the uniform weak topology of Chen et al. (2010) or the universal strategic topology of Dekel et al. (2006), both of which ensure that strategic behaviour exhibits desirable continuity properties.