2405.00165
Solvable Initial Value Problems Ruled by Discontinuous Ordinary Differential Equations
Olivier Bournez, Riccardo Gozzi
correctmedium confidence
- Category
- Not specified
- Journal tier
- Strong Field
- Processed
- Sep 28, 2025, 12:56 AM
- arXiv Links
- Abstract ↗PDF ↗
Audit review
The paper proves two key facts: (i) if f is solvable (Baire–1 and with closed discontinuity sets on all closed subdomains), then the f-removed sequence stabilizes at a countable stage (Theorem 9, via the Cantor–Baire stationary principle, Theorem 6), and (ii) the unique solution of the IVP can be obtained analytically by a concrete transfinite search-and-glue construction ((α)Monkeys approach) that converges to the solution (Theorem 10) . The candidate solution correctly rederives the countable termination of the removed-set process using standard Baire–1 facts and a rational-balls injection argument, which is compatible with the paper’s Theorem 9 and Lemma 2 (meagerness/Fσ of discontinuities) . However, its final “construction” of the solution is circular: it defines ranks using the unknown solution y and assumes uniqueness/continuity on layers to “glue” solution segments, instead of providing the analytic, non-circular transfinite procedure that the paper develops ((α)Monkeys). Thus, while the candidate’s termination argument is fine, it fails to supply the analytic transfinite construction required by Theorem 10. The paper’s argument is complete on both points; the model’s solution is incomplete/wrong on the constructive step.
Referee report (LaTeX)
\textbf{Recommendation:} minor revisions \textbf{Journal Tier:} strong field \textbf{Justification:} The paper introduces a robust solvability notion for discontinuous IVPs with unique solutions, proves countable termination of the removed-set hierarchy, and provides an analytic transfinite construction to obtain the solution. The results connect classical Baire-category methods to constructive procedures reminiscent of Denjoy’s totalization. Examples illustrate the hierarchy and computational implications. Minor expository refinements would improve accessibility of the main construction.