Topological manipulators form an ultrafilter

摘要

Consider the problem of aggregating preferences. A coalition is manipulative if it is able to force the outcome of the aggregation process. In the framework of topological aggregation (due to Chichilnisky) the family of manipulative coalitions constitutes an ultrafilter. This result holds for finite and for infinite populations, and supports the analogy between the Chichilnisky and the Arrovian aggregation model.This text presents research results of the Belgian Programme of Interuniversity Poles of Attraction initiated under the Science Policy Programmes of the Prime Ministers Office, Belgium. The scientific responsibility is assumed by its authors. I thank the referee for her/his constructive comments.