2006.04783
DISTINGUISHING ENDPOINT SETS FROM ERDŐS SPACE
David S. Lipham
correcthigh confidence
- Category
- math.DS
- Journal tier
- Specialist/Solid
- Processed
- Sep 28, 2025, 12:55 AM
- arXiv Links
- Abstract ↗PDF ↗
Audit review
The paper proves that the escaping endpoint set Ė(f) for f(z)=e^z−1 is not homeomorphic to Q×X for any space X via a brush-model plus a topological lemma and an explicit simple-closed-curve construction around endpoints; the argument is coherent and complete in the provided text (see the statement of Theorem 1 and its proof outline and completion) . By contrast, the model’s proof hinges on unproven—and likely false—claims: (i) that the escaping endpoints Ė(f) are homeomorphic to an open subset of Z^N (hence Polish/Baire), and (ii) that the address–endpoint map is a homeomorphism on the subspace of addresses with positive minimal potential. The paper’s brush model does not imply these topological identifications; in particular, the set Σ_fast={s:t_s>0} need not be open in the product topology on Z^N, and “escaping endpoint = t_s>0” is not justified. Consequently, the model’s Baire-vs-meagre argument lacks the required foundations.
Referee report (LaTeX)
\textbf{Recommendation:} minor revisions
\textbf{Journal Tier:} specialist/solid
\textbf{Justification:}
A concise and well-motivated note that cleanly separates the topology of escaping endpoints from the class Q×X by an elegant geometric argument in the brush model. The proof is correct as written and yields additional insight (a simple closed curve separating each escaping endpoint from infinity, and path-connectedness of the complement). A few minor clarifications in the construction could further improve readability.