Fields Institute Monographs 1997; 165 pp; hardcover Volume: 8 Reprint/Revision History: reprinted with corrections 1998 ISBN10: 0821806025 ISBN13: 9780821806029 List Price: US$56 Member Price: US$44.80 Order Code: FIM/8
 The nature of \(C^*\)algebras is such that one cannot study perturbation without also studying the theory of lifting and the theory of extensions. Approximation questions involving representations of relations in matrices and \(C^*\)algebras are the central focus of this volume. A variety of approximation techniques are unified by translating them into lifting problems: from classical questions about transitivity of algebras of operators on Hilbert spaces to recent results in linear algebra. One chapter is devoted to Lin's theorem on approximating almost normal matrices by normal matrices. The techniques of universal algebra are applied to the category of \(C^*\)algebras. An important difference, central to this book, is that one can consider approximate representations of relations and approximately commuting diagrams. Moreover, the highly algebraic approach does not exclude applications to very geometric \(C^*\)algebras. \(K\)theory is avoided, but universal properties and stability properties of specific \(C^*\)algebras that have applications to \(K\)theory are considered. Index theory arises naturally, and very concretely, as an obstruction to stability for almost commuting matrices. Multiplier algebras are studied in detail, both in the setting of rings and of \(C^*\)algebras. Recent results about extensions of \(C^*\)algebras are discussed, including a result linking amalgamated products with the Busby/Hochshild theory. Titles in this series are copublished with The Fields Institute for Research in Mathematical Sciences (Toronto, Ontario, Canada). Readership Reviews "Loring deals, in a beautifully organised and systematic manner, with a wide swathe of modern \(C^*\)algebra theory, covering such topics as generators and relations, multipliers and corona algebras, extendibility, lifting, projectivity and semiprojectivity. There is a marked algebraic flavour to much of the book, and Loring has been careful to separate out those sections that are purely ringtheoretic in nature. Algebraists are beginning to discover some of the rich structure that nonunital rings can possess, and they should find much of interest here. Loring has done a superb job in assembling a mass of powerful machinery ... Every operator algebraist will want a copy of this book."  Bulletin of the London Mathematical Society Table of Contents Part I. Rings and \(C^*\)algebras  \(\sigma\)unital \(C*\)algebras
 Order and factoring
 Generators and relations
 Basic perturbation
 Pushouts and pullbacks
 Matrix algebras
 Multipliers
Part II.Lifting  Easy lifting
 Multiplier algebras
 Projectivity
 Properties of projective \(C^*\)algebras
 Heavy lifting
Part III. Perturbing  Inductive limits
 Stable relations
 Applications
 Extensions
Part IV. Almost Normal  Normals, limits
 Almost normal elements
 Almost normal matrices
 Bibliography
 Index
