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Paper   IPM / M / 17267
School of Mathematics
  Title:   Finite group and integer actions on simple tracially Z-absorbing $C^{*}$-algebras
  Author(s):  Nasser Golestani (Joint with M. Amini, S. Jamali, and N. Christopher Phillips)
  Status:   To Appear
  Journal: J. Operator Theory
  Supported by:  IPM
We show that if $A$ is a simple (not necessarily unital) tracially $\mathcal{Z}$-absorbing C*-algebra and $\alpha \colon G \to \mathrm{Aut} (A)$ is an action of a finite group $G$ on $A$ with the weak tracial Rokhlin property, then the crossed product $C^*(G, A,\alpha)$ and the fixed point algebra $A^\alpha$ are simple and tracially $\mathcal{Z}$-absorbing, and they are $\mathcal{Z}$-stable if, in addition, $A$ is separable and nuclear. The same conclusion holds for all intermediate C*-algebras of the inclusions $A^\alpha \subseteq A$ and $A \subseteq C^*(G, A,\alpha)$. We prove that if $A$ is a simple tracially $\mathcal{Z}$-absorbing C*-algebra, then, under a finiteness condition, the permutation action of the symmetric group $S_m$ on the minimal $m$-fold tensor product of $A$ has the weak tracial Rokhlin property. We define the weak tracial Rokhlin property for automorphisms of simple C*-algebras and we show that---under a mild assumption---(tracial) $\mathcal{Z}$-absorption is preserved under crossed products by such automorphisms.

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