Set Center for Advanced Studies in Economic Theory Arbitrage and Equilibrium with Exchangeable Risks Aviad Heifetz Enrico Minelli H. M. Polemarchakis Working Paper n. 06/00 Set Center for Advanced Studies in Economic Theory Universita’ degli Studi di Milano Bicocca Via Bicocca degli Arcimboldi, 8 20126 Milan - Italy Ph. ++39-026448.7358; Fax ++39-02647.3312 E-mail:set.center@unimib.it http://www.unimib.it/set University of Milan-Bicocca