Reduced $C^{*}$-algebras of Product Systems -- an $E_0$-semigroup and a Groupoid perspective

Md Amir Hossain; S. Sundar

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arXiv · 2507.20319

Reduced $C^{*}$-algebras of Product Systems -- an $E_0$-semigroup and a Groupoid perspective

Md Amir Hossain·S. Sundar

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Abstract

For Ore semigroups $P$ with an order unit, we prove that there is a bijection between $E_0$-semigroups over $P$ and product systems of $C^{*}$-correspondences over $P^{op}$. We exploit this bijection and show that the reduced $C^{*}$-algebra of a proper product system is Morita equivalent to the reduced crossed product of the associated semigroup dynamical system given by the corresponding $E_0$-semigroup. We appeal to the groupoid picture of the reduced crossed product of a semigroup dynamical system derived in [47] to prove that, under good conditions, the reduced $C^{*}$-algebra of a proper product system is nuclear/exact if and only if the coefficient algebra is nuclear/exact. We also discuss the invariance of $K$-theory under homotopy of product systems.

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BibTeX RIS

Md Amir Hossain, S. Sundar. 2025-07-27. Reduced $C^{*}$-algebras of Product Systems -- an $E_0$-semigroup and a Groupoid perspective. https://arxiv.org/abs/2507.20319

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