2110.11727
ABUNDANCE OF OBSERVABLE LYAPUNOV IRREGULAR SETS
Shin Kiriki, Xiaolong Li, Yushi Nakano, Teruhiko Soma
correctmedium confidence
- Category
- Not specified
- Journal tier
- Strong Field
- Processed
- Sep 28, 2025, 12:56 AM
- arXiv Links
- Abstract ↗PDF ↗
Audit review
The paper establishes Theorem A: for some g in a Newhouse open set (r≥2), every sufficiently small neighborhood O of g contains an uncountable family L of diffeomorphisms that are pairwise non-topologically-conjugate; for each f in L there are open sets U_f and cone V_f such that every x in U_f is Lyapunov-irregular for all nonzero v in V_f, and L splits into uncountable subfamilies R (Birkhoff-regular on U_f) and I (Birkhoff-irregular on U_f). This statement and its proof are presented explicitly and in detail, including the Colli–Vargas return-map setup, the control of higher-order terms, and the construction of the uncountable, non-conjugate families with the Birkhoff dichotomy (see Theorem A and Section 4, including Theorem 4.8 and the concluding argument) . By contrast, the candidate solution hinges on a stronger, unproven premise: it assumes as input that within any Newhouse open set there is a dense subset of maps already exhibiting the open-set Lyapunov-irregular property with a Birkhoff regular/irregular dichotomy, attributed to the same 2021 paper. The paper itself does not prove that dense-subset statement; rather, it proves the existence of a specific g with the desired neighborhood-universal property and remarks that a dense-set extension is plausible, not established. Consequently, the model’s Step (A) misstates the available result and uses it critically to select f_R and f_I in an arbitrary small neighborhood O; this logical gap undermines the model’s argument even though its later use of periodic-spot technology (Turaev) could, in principle, supply a different route to non-conjugacy. In short: the paper’s argument is correct and complete for the stated theorem, while the model’s solution relies on a non-cited, unproven strengthening.
Referee report (LaTeX)
\textbf{Recommendation:} minor revisions
\textbf{Journal Tier:} strong field
\textbf{Justification:}
The manuscript establishes a substantial and technically sophisticated result on the abundance (indeed, uncountable multiplicity up to conjugacy) of diffeomorphisms near robust homoclinic tangencies whose Lyapunov exponents fail to exist on open sets, together with a Birkhoff regular/irregular dichotomy on those sets. The construction, grounded in the Colli–Vargas framework and careful derivative estimates on return maps, convincingly achieves the claimed phenomena. A few expository clarifications (e.g., more detail on the non-conjugacy distinction and on how the coding implies uncountability up to conjugacy) would further enhance readability.