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On free Stein dimension

Charlesworth, Ian and Nelson, Brent 2025. On free Stein dimension. Indiana University Mathematics Journal

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Abstract

We establish several properties of the free Stein dimension, an invariant for finitely generated unital tracial *-algebras. We give formulas for its behaviour under direct sums and tensor products with finite dimensional algebras. Among a given set of generators, we show that (approximate) algebraic relations produce (non-approximate) bounds on the free Stein dimension. Particular treatment is given to the case of separable abelian von Neumann algebras, where we show that free Stein dimension is a von Neumann algebra invariant. In addition, we show that under mild assumptions L2-rigidity implies a free Stein dimension of one. Finally, we use limits superior/inferior to extend the free Stein dimension to a von Neumann algebra invariant—which is substantially more difficult to compute in general—and compute it in several cases of interest.

Item Type: Article
Date Type: Published Online
Status: In Press
Schools: Schools > Mathematics
Publisher: Indiana University Mathematics Journal
ISSN: 0022-2518
Date of First Compliant Deposit: 17 January 2024
Date of Acceptance: 6 January 2024
Last Modified: 04 Jun 2025 11:45
URI: https://orca.cardiff.ac.uk/id/eprint/165568

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