This volume consists of articles contributed by participants at the fourth Ja pan-U.S. Joint Seminar on Operator Algebras. The seminar took place at the University of Pennsylvania from May 23 through May 27, 1988 under the auspices of the Mathematics Department. It was sponsored and supported by the Japan Society for the Promotion of Science and the National Science Foundation (USA). This sponsorship and support is acknowledged with gratitude. The seminar was devoted to discussions and lectures on results and prob lems concerning mappings of operator algebras (C*-and von Neumann alge bras). Among the articles contained in these proceedings, there are papers dealing with actions of groups on C* algebras, completely bounded mappings, index and subfactor theory, and derivations of operator algebras. The seminar was held in honor of the sixtieth birthday of Sh6ichir6 Sakai, one of the great leaders of Functional Analysis for many decades. This vol ume is dedicated to Professor Sakai, on the occasion of that birthday, with the respect and admiration of all the contributors and the participants at the seminar. H. Araki Kyoto, Japan R. Kadison Philadelphia, Pennsylvania, USA Contents Preface.... ..... ....... ........... ...... ......... ................ ...... ............... ... vii On Convex Combinations of Unitary Operators in C*-Algebras UFFE HAAGERUP ......................................................................... .

Inhalt
On Convex Combinations of Unitary Operators in C*-Algebras.- Approximately Inner Derivations, Decompositions and Vector Fields of Simple C*-Algebras.- Derivations in Commutative C*-Algebras.- Representation of Quantum Groups.- Automorphism Groups and Covariant Irreducible Representations.- Proper Actions of Groups on C*-Algebras.- On the Baum-Connes Conjecture.- On Primitive Ideal Spaces of C*-Algebras over Certain Locally Compact Groupoids.- On Sequences of Jones' Projections.- The Powers' Binary Shifts on the Hyperfinite Factor of Type II1.- Index Theory for Type III Factors.- Relative Entropy of a Fixed Point Algebra.- Jones Index Theory for C*-Algebras.- Three Tensor Norms for Operator Spaces.- Extension Problems for Maps on Operator Systems.- Multivariable Toeplitz Operators and Index Theory.- On Maximality of Analytic Subalgebras Associated with Flow in von Neumann Algebras.- Reflections Relating a von Neumann Algebra and Its Commutant.- Normal AW*-Algebras.