2110.10265
Hölder Continuity of the Lyapunov Exponents of Linear Cocycles over Hyperbolic Maps
Pedro Duarte, Silvius Klein, Mauricio Poletti
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 local Hölder continuity of all Lyapunov exponents near typical, fiber‑bunched cocycles by first establishing a uniform large‑deviations type estimate (via a fiber strong‑mixing Markov operator construction) and then invoking an abstract continuity theorem to derive a Hölder modulus; see Theorem 1.1, Theorem 7.1 and Theorem 7.2, and the exterior‑power reduction to all exponents (Theorems 2.2–2.3) . By contrast, the model’s argument critically asserts uniform exponential convergence of the finite‑time averages (1/n)∫log||∧^k B_n|| dμ to Λ_k(B) from an LDT of the form μ{|(1/n)log||∧^k B_n||−Λ_k|>ε} ≤ Ce^{-kε^2 n}. That conclusion does not follow from such LDT bounds (optimizing ε yields only O(n^{-1/2})-type control on the mean deviation, not an exponential rate). The paper avoids this pitfall and obtains Hölder continuity through the abstract continuity theorem, rather than through an (incorrect) exponential speed of convergence of expectations . The model also misattributes the source of uniform LDT to quasi‑multiplicativity (Park); in the paper, the LDT is obtained via strong mixing of a Markov operator on the projectivized bundle and holonomy reduction, not via Park’s approach .
Referee report (LaTeX)
\textbf{Recommendation:} minor revisions
\textbf{Journal Tier:} strong field
\textbf{Justification:}
The paper proves local Hölder continuity of Lyapunov exponents for typical, fiber-bunched cocycles via a robust and well-motivated pipeline: holonomy reduction, a fiber strong-mixing Markov operator, a uniform LDT, and an abstract continuity theorem. The arguments are technically careful and the results are significant, with additional statistical consequences. Minor edits could further clarify where constants are uniform and how the abstract continuity theorem is applied.