The Weak Tracial Rokhlin Property for Finite Group Actions on Simple C*-Algebras

摘要

We develop the concept of weak tracial Rokhlin property for finite group actions on simple (not necessarily unital) C*-algebras and study its properties systematically. In particular, we show that this property is stable under restriction to invariant hereditary C*-algebras, minimal tensor products, and direct limits of actions. Some of these results are new even in the unital case and answer open questions asked by N. C. Phillips in full generality. We present several examples of finite group actions with the weak tracial Rokhlin property on simple stably projectionless C*-algebras. We prove that if (lpha colon G ightarrow ext{Aut}(A)) is an action of a finite group (G) on a simple C*-algebra (A) with tracial rank zero and (lpha) has the weak tracial Rokhlin property, then the crossed product (A times_{lpha} G) and the fixed point algebra (A^{lpha}) are simple with tracial rank zero. This extends a result of N. C. Phillips to the nonunital case. We use the machinery of Cuntz subequivalence to work in this nonunital setting.