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2105.00479

CONJUGACY OF LOCAL HOMEOMORPHISMS VIA GROUPOIDS AND C*-ALGEBRAS

Becky Armstrong, Kevin Aguyar Brix, Toke Meier Carlsen, Søren Eilers

correcthigh confidence
Category
Not specified
Journal tier
Strong Field
Processed
Sep 28, 2025, 12:56 AM

Audit review

The candidate reproduces the equivalence in Theorem 3.1 for second-countable Deaconu–Renault systems using the same three pillars as the paper: (i) a C0-level characterisation (Proposition 3.4), (ii) a groupoid/cocycle characterisation (Proposition 3.8), and (iii) a C*-algebraic characterisation via weighted actions plus groupoid reconstruction (Lemma 3.10 and Proposition 3.12). The paper’s statements and proofs explicitly appear in 3.4, 3.8, 3.10, 3.12 and the summary Theorem 3.1, and the candidate’s route mirrors these steps with only minor stylistic differences (e.g., an explicit “edge test” to pin down ψ on Z(X,1,0,σX(X))). One small nuance is that, where the paper requires a “separating” group in some implications, the candidate instantiates Γ = ℝ and argues the diagonal as the joint fixed-point algebra directly; this is consistent with the theorem as stated over ℝ. Overall, the arguments agree line-by-line with the paper’s logic and dependencies.

Referee report (LaTeX)

\textbf{Recommendation:} minor revisions

\textbf{Journal Tier:} strong field

\textbf{Justification:}

The paper provides a comprehensive characterisation of conjugacy for Deaconu–Renault systems via groupoid and C*-algebra invariants, extending prior results and unifying several perspectives. The proofs are sound and well-structured. Minor clarifications regarding the role of separating groups versus the R-formulation, and a few expository enhancements, would further improve readability.