Quadratic subproduct systems, free products, and their C*-algebras

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Hauptverfasser: Arici, Francesca, Ge, Yufan
Format: Preprint
Veröffentlicht: 2025
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author Arici, Francesca
Ge, Yufan
author_facet Arici, Francesca
Ge, Yufan
contents Motivated by the interplay between quadratic algebras, noncommutative geometry, and operator theory, we introduce the notion of quadratic subproduct systems of Hilbert spaces. Specifically, we study the subproduct systems induced by a finite number of complex quadratic polynomials in noncommuting variables, and describe their Toeplitz and Cuntz--Pimsner algebras. Inspired by the theory of graded associative algebras, we define a free product operation in the category of subproduct systems and show that this corresponds to the reduced free product of the Toeplitz algebras. Finally, we obtain results about the K-theory of the Toeplitz and Cuntz--Pimsner algebras of a large class of quadratic subproduct systems.
format Preprint
id arxiv_https___arxiv_org_abs_2504_12843
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Quadratic subproduct systems, free products, and their C*-algebras
Arici, Francesca
Ge, Yufan
Operator Algebras
K-Theory and Homology
Quantum Algebra
Rings and Algebras
Motivated by the interplay between quadratic algebras, noncommutative geometry, and operator theory, we introduce the notion of quadratic subproduct systems of Hilbert spaces. Specifically, we study the subproduct systems induced by a finite number of complex quadratic polynomials in noncommuting variables, and describe their Toeplitz and Cuntz--Pimsner algebras. Inspired by the theory of graded associative algebras, we define a free product operation in the category of subproduct systems and show that this corresponds to the reduced free product of the Toeplitz algebras. Finally, we obtain results about the K-theory of the Toeplitz and Cuntz--Pimsner algebras of a large class of quadratic subproduct systems.
title Quadratic subproduct systems, free products, and their C*-algebras
topic Operator Algebras
K-Theory and Homology
Quantum Algebra
Rings and Algebras
url https://arxiv.org/abs/2504.12843