Exactness of Reduced Amalgamated Free Product C {algebras

A Relationship between Hnn Extensions and Amalgamated Free Products in Operator Algebras

By improving the previous construction in [18] we observe that any reduced HNN extension is a corner of a certain reduced amalgamated free product in both the von Neumann algebra and the C∗-algebra settings. Then, the same fact is shown for universal HNN extensions of C∗-algebras. We apply the observation to the questions of factoriality and type classification of HNN extensions of von Neumann ...

Topological Entropy of Some Automorphisms of Reduced Amalgamated Free Product C–algebras

Certain classes of automorphisms of reduced amalgamated free products of C∗– algebras are shown to have Brown–Voiculescu topological entropy zero. Also, for automorphisms of exact C∗–algebras, the Connes–Narnhofer–Thirring entropy is shown to be bounded above by the Brown–Voiculescu entropy. These facts are applied to generalize Størmer’s result about the entropy of automorphisms of the II1–fac...

On Embeddings of Full Amalgamated Free Product C∗–algebras

An embedding question for full (i.e. universal) amalgamated free products of C∗–algebras is raised, and solved in part. This is used to give a necessary and sufficient condition for the full amalgamated free product of finite dimensional C∗–algebras to be residually finite dimensional.

Institute for Mathematical Physics Topological Entropy of Some Automorphisms of Reduced Amalgamated Free Product C {algebras

On Embeddings of Full Amalgamated Free Product C–algebras Revised and Expanded Version

We examine the question of when the ∗–homomorphism λ : A ∗D B → Ã ∗ D̃ B̃ of full amalgamated free product C∗–algebras, arising from compatible inclusions of C∗–algebras A ⊆ Ã, B ⊆ B̃ and D ⊆ D̃, is an embedding. Results giving sufficient conditions for λ to be injective, as well of classes of examples where λ fails to be injective, are obtained. As an application, we give necessary and sufficient ...