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2505.02308

Enabling Local Neural Operators to perform Equation-Free System-Level Analysis

Gianluca Fabiani, Hannes Vandecasteele, Somdatta Goswami, Constantinos Siettos, Ioannis G. Kevrekidis

incompletemedium confidence
Category
Not specified
Journal tier
Specialist/Solid
Processed
Sep 28, 2025, 12:56 AM

Audit review

The paper clearly formulates the EF residual ψ(u;λ) = u − ST[u,λ], advocates Jacobian-free Newton–GMRES, Arnoldi stability analysis, and pseudo‑arclength continuation for neural-operator timesteppers, and demonstrates these numerically; however, it does not provide rigorous convergence, error, or perturbation bounds beyond heuristic discussion and standard algorithmic descriptions. See the paper’s definitions and EF setup, including ψ and ST, and the matrix-free JVP via finite differences and Newton–GMRES, as well as the continuation and Arnoldi details in the main text and Appendix E . The homotopy-based embedding and empirical spectral accuracy claims are described but not proved theoretically; the Bauer–Fike rationale appears only as qualitative guidance . The candidate model solution supplies a plausible theoretical framework (Newton–Kantorovich, implicit function/pseudo‑arclength, spectral perturbation) but leans on an overly strong contraction assumption for ST that cannot hold near unstable equilibria and mixes state and derivative consistency in a key composition error bound; thus, it is also incomplete.

Referee report (LaTeX)

\textbf{Recommendation:} major revisions

\textbf{Journal Tier:} specialist/solid

\textbf{Justification:}

The paper convincingly demonstrates, through careful experiments, that local NO timesteppers can be wrapped in equation-free algorithms (Newton–GMRES, Arnoldi, pseudo-arclength) to recover steady states, leading multipliers, and bifurcation structure. However, theoretical guarantees are absent. Adding clear assumptions and at least local, conditional results would substantively strengthen the contribution. The candidate model solution indicates a viable theoretical path but itself uses an over-strong contraction assumption and an imprecise composition error bound; these should be corrected and aligned with IFT/perturbation arguments that cover unstable equilibria.