English

Reconstruction of topological graphs and their Hilbert bimodules

Operator Algebras 2025-04-30 v2

Abstract

We show that the Hilbert bimodule associated to a compact topological graph can be recovered from the C*-algebraic triple consisting of the Toeplitz algebra of the graph, its gauge action and the commutative subalgebra of functions on the vertex space of the graph. We discuss connections with work of Davidson-Katsoulis and of Davidson-Roydor on local conjugacy of topological graphs and isomorphism of their tensor algebras. In particular, we give a direct proof that a compact topological graph can be recovered up to local conjugacy from its Hilbert bimodule, present an example of nonisomorphic locally conjugate compact topological graphs with isomorphic Hilbert bimodules. We also give an elementary proof that for compact topological graphs with totally disconnected vertex space the notions of local conjugacy, Hilbert bimodule isomorphism, isomorphism of C*-algebraic triples, and isomorphism all coincide.

Keywords

Cite

@article{arxiv.2212.09195,
  title  = {Reconstruction of topological graphs and their Hilbert bimodules},
  author = {Rodrigo Frausino and Abraham C. S. Ng and Aidan Sims},
  journal= {arXiv preprint arXiv:2212.09195},
  year   = {2025}
}

Comments

V2: 24 pages. Added references to earlier work, especially of Davidson-Katsoulis, Davidson-Roydor for the origin of local conjugacy of topological graphs and related results/examples, and of Bruce-Takeishi on reconstruction of discrete graphs; apologies for our oversight. Thanks to Adam Dor-On and an anonymous referee for alerting us, and Davidson and Katsoulis for helpful discussions