<p>In this paper, we introduce compact group actions with the weak tracial Rokhlin property. This concept generalizes both the finite group actions with the weak tracial Rokhlin property and the compact group actions with the tracial Rokhlin property on classifiable C*-algebras (in the sense of the Elliott program). Under this framework, we prove that simplicity, pure infiniteness, tracial <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\mathcal {Z}\)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="script">Z</mi> </math></EquationSource> </InlineEquation>-stability and the combination of nuclearity and <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(\mathcal {Z}\)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="script">Z</mi> </math></EquationSource> </InlineEquation>-stability can be transferred from the original algebra to the crossed product. We also show that the radius of comparison of the fixed point algebra does not exceed that of the original algebra. Furthermore, we discuss the relationship between our definition and natural generalization of the finite group case in non-Elliott program settings. Finally, we provide a nontrivial example of a compact group action with the weak tracial Rokhlin property with comparison: an action of <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\((S_2)^{\mathbb {N}}\)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mrow> <mo stretchy="false">(</mo> <msub> <mi>S</mi> <mn>2</mn> </msub> <mo stretchy="false">)</mo> </mrow> <mi mathvariant="double-struck">N</mi> </msup> </math></EquationSource> </InlineEquation> on the Jiang-Su algebra <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(\mathcal {Z}\)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="script">Z</mi> </math></EquationSource> </InlineEquation>. Since <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(\mathcal {Z}\)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="script">Z</mi> </math></EquationSource> </InlineEquation> contains no nontrivial projections, this action does not possess the tracial Rokhlin property.</p>

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Crossed products by compact group actions with the weak tracial Rokhlin property

  • Xiaochun Fang,
  • Haotian Tian

摘要

In this paper, we introduce compact group actions with the weak tracial Rokhlin property. This concept generalizes both the finite group actions with the weak tracial Rokhlin property and the compact group actions with the tracial Rokhlin property on classifiable C*-algebras (in the sense of the Elliott program). Under this framework, we prove that simplicity, pure infiniteness, tracial \(\mathcal {Z}\) Z -stability and the combination of nuclearity and \(\mathcal {Z}\) Z -stability can be transferred from the original algebra to the crossed product. We also show that the radius of comparison of the fixed point algebra does not exceed that of the original algebra. Furthermore, we discuss the relationship between our definition and natural generalization of the finite group case in non-Elliott program settings. Finally, we provide a nontrivial example of a compact group action with the weak tracial Rokhlin property with comparison: an action of \((S_2)^{\mathbb {N}}\) ( S 2 ) N on the Jiang-Su algebra \(\mathcal {Z}\) Z . Since \(\mathcal {Z}\) Z contains no nontrivial projections, this action does not possess the tracial Rokhlin property.