Tron Omland

Primeness and primitivity conditions for twisted group C∗ -algebras

For a multiplier (2-cocycle)

C⁎-simplicity of free products with amalgamation and radical classes of groups

\sigma

The full group C -algebra of the modular group is primitive

on a discrete group

On the K-theory of C*-algebras arising from integral dynamics

G

C∗-Algebras Associated with a-adic Numbers

we give conditions for which the twisted group

Rigidity theory for C∗-dynamical systems and the “Pedersen rigidity problem”

C^*

On twisted group -algebras associated with FC-hypercentral groups and other related groups

-algebra associated with the pair

PRIMITIVITY OF SOME FULL GROUP C -ALGEBRAS

(G,\sigma)

On reduced twisted group C*-algebras that are simple and/or have a unique trace

is prime or primitive. We also discuss how these conditions behave on direct products and free products of groups.

Three versions of categorical crossed-product duality

Abstract We give new characterizations to ensure that a free product of groups with amalgamation has a simple reduced group C ⁎ -algebra, and provide a concrete example of an amalgam with trivial kernel, such that its reduced group C ⁎ -algebra has a unique tracial state, but is not simple. Moreover, we show that there is a radical class of groups for which the reduced group C ⁎ -algebra of any group is simple precisely when the group has a trivial radical corresponding to this class.