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arXiv 2011.06686math.OAmath.DS
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正合离散群的部分交叉积的核性

Nuclearity for partial crossed products by exact discrete groups

Alcides Buss, Damián Ferraro, Camila F. Sehnem

摘要:

研究了正合离散群在C* 代数上的部分作用。证明了交换C* 代数-代数与正合离散群的部分交叉积是核的,只要完全交叉积与约化部分交叉积重合.这概括了松村在全球行动背景下的一个结果。在一般情况下,我们证明了C* 代数$A$上的正合离散群的部分作用具有Exel逼近性质当且仅当与$A\otimes_{\max} A^\mathrm{op}$上的对角部分作用相关联的完全和约化部分交叉积重合.我们应用这些结果证明了正合离散群的子幺半群的约化半群C*-代数$\mathrm{C}^*_λ(P)$是核的,如果$\ell^2(P)$上的左正则表示是全C*-代数与约化C* 代数之间的同构.我们还证明了在与分离图相关联的C* 代数的情况下,核性等价于弱包含性。

英文摘要:

We study partial actions of exact discrete groups on C*-algebras. We show that the partial crossed product of a commutative C*-algebra by an exact discrete group is nuclear whenever the full and reduced partial crossed products coincide. This generalises a result by Matsumura in the context of global actions. In general, we prove that a partial action of an exact discrete group on a C*-algebra $A$ has Exel's approximation property if and only if the full and reduced partial crossed products associated to the diagonal partial action on $A\otimes_{\max} A^\mathrm{op}$ coincide. We apply our results to show that the reduced semigroup C*-algebra $\mathrm{C}^*_λ(P)$ of a submonoid of an exact discrete group is nuclear if the left regular representation on $\ell^2(P)$ is an isomorphism between the full and reduced C*-algebras. We also show that nuclearity is equivalent to the weak containment property in the case of C*-algebras associated to separated graphs.

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