2207.00875
The dud canard: Existence of strong canard cycles in R3
Kristiansen, K. U.
correctmedium confidence
- Category
- Not specified
- Journal tier
- Specialist/Solid
- Processed
- Sep 28, 2025, 12:56 AM
- arXiv Links
- Abstract ↗PDF ↗
Audit review
The paper proves Theorem 1.1 in the analytic setting via a two-chart blow-up analysis that constructs (i) small Hopf-born cycles in the ε̄=1 chart using an analytic slow manifold and a Melnikov-type return map, and (ii) intermediate cycles in the x̄=−1 chart via transition maps and then glues these families to obtain the full branch Γ_{h,ε} with µ(h,ε) and Hausdorff convergence to singular canard cycles; see the setting (3)–(5) and the statement of Theorem 1.1 (µ=µ_H(√ε), µ_H(0)=0) and its proof architecture in Sections 2–4 . By contrast, the model’s solution asserts a global Poincaré map that is a small C^1 perturbation of the identity and even posits that the singular return map is the identity, from which it applies an IFT in µ. These steps sidestep the zero-Hopf nonuniformity and the need for analyticity stressed in the paper (for extending a normally elliptic slow manifold and setting up a uniform return map near the Hopf) and they omit the chart-wise construction and gluing that the paper makes essential . The model also does not justify the claimed transversality of the return map’s µ-dependence at ε=0 nor the O(√ε) near-identity estimate for the global map. Hence, while the model states the correct high-level result, its proof outline relies on unjustified or false claims (e.g., singular map ≡ identity) and misses key hypotheses (analyticity), making it incorrect as a proof.
Referee report (LaTeX)
\textbf{Recommendation:} minor revisions \textbf{Journal Tier:} specialist/solid \textbf{Justification:} This paper gives a rigorous and conceptually clear account of the birth and continuation of strong canard cycles through a folded saddle-node of type II in three dimensions, including the singular Hopf connection. The use of a two-chart blow-up, analytic slow manifold construction, and a Melnikov-style return map near the Hopf, followed by a careful gluing with intermediate orbits, offers a sound extension of the planar canard-explosion framework to R3. The contribution is specialized but solid and timely. Minor revisions are recommended to improve exposition and to delineate more explicitly the role of analyticity and the scope of uniformity near the zero-Hopf limit.