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Voltage quantum graphs and a Gross-Tucker theorem for quantum graphs
Björn Schäfer, Mariusz Tobolski
A voltage graph is a finite directed graph whose edges are labeled by elements of a finite group . A classical construction of Gross and Tucker associates to every voltage graph…
Hypercube C*-algebras and an application to magic isometries
Björn Schäfer
We study C*-algebras generated by two partitions of unity with orthogonality relations governed by hypercubes for . These "hypercube C*-alge…
Classification of Certain C*-Algebras Generated by Two Partitions of Unity
Björn Schäfer
We study C*-algebras generated by two partitions of unity subject to orthogonality relations governed by a bipartite graph which we also call "bipartite graph C*-algebras". These a…
Complete Classification of Directed Quantum Graphs on M2
Nina Kiefer, Björn Schäfer
In 2022, Gromada and Matsuda classified undirected quantum graphs on the matrix algebra . Later, Wasilweski provided a solid theory of directed quantum graphs which was former…
Nuclearity of Hypergraph C*-Algebras
Björn Schäfer, Moritz Weber
We partially characterize nuclearity for the recently introduced class of hypergraph C*-algebras using a tailor-made hypergraph minor relation. The latter is generated by certain o…