2025/05/23 by Duwenig, Anna
#22A22 #46L05 #46L55 #FOS: Mathematics #Operator Algebras (math.OA)
paper · doi:10.48550/arxiv.2505.17913
We identify which conditions on an open normal subgroupoid of a LCH étale groupoid with twist are necessary and sufficient for the subgroupoid's reduced twisted C*-algebra to be a C*-diagonal in the ambient groupoid C*-algebra. We do so by first giving an explicit description of the Weyl groupoid and Weyl twist associated to any non-traditional Cartan subalgebra, that is, a Cartan subalgebra that is induced from a non-trivial open normal subgroupoid, as studied in [DWZ2025]. We then combine this description with Kumjian-Renault theory to establish the necessary and sufficient conditions to get a C*-diagonal.