Topological entropy of some automorphisms of reduced amalgamated free product C*-algebras

Certain classes of automorphisms of recued 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 Stormer's result about entropy of automorphisms of the II_1-factor of a free group.Comment: 13 page

Free subproducts and free scaled products of II_1 factors

The constructions of free subproducts of von Neumann algebras and free scaled products are introduced, and results about them are proved, including rescaling results and results about free trade in free scaled products.Comment: 30 page

On certain free product factors via an extended matrix model

Voiculescu's random matrix model for freeness is extended to the non-Gaussian case and also the case of constant block diagonal matrices. Thus we are able to investigate free products of free group factors with matrix algebras and with the hyperfinite II$_1$ factor, showing that $$L(F_n) * R = L(F_(n+1))$$ for $n \ge 1$, (where $L(F_1)=L(Z)$).Comment: 19+3 pages, AMSTeX 2.1 (figures in LaTeX 2.09), KD-at-UCB-00

Free products of exact groups

It has recently been proved that the class of unital exact C*-algebras is closed under taking reduced amalgamated free products. In particular, this implied that the class of exact discrete groups is closed under taking amalgamated free products. Here a proof is presented of a special case: that the class of exact discrete groups is closed under taking free products (with amalgamation over the identity element). The proof of this special case is considerably simpler than in full generality.Comment: 9 pages, to appear in the proceedings volume of the conference on C*-algebras in Muenster, March, 199