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2506.04124

Hölder continuity of Lyapunov exponents for non-invertible and non-compact random cocycles

Pedro Duarte, Tomé Graxinha

correcthigh confidence
Category
Not specified
Journal tier
Strong Field
Processed
Sep 28, 2025, 12:56 AM

Audit review

The paper proves local Hölder continuity of the top Lyapunov exponent in the Wasserstein metric near a quasi-irreducible measure with a spectral gap (Theorem 2.1), via a spectral/Markov-operator method yielding uniform strong mixing on Hölder observables and a careful truncation/tail analysis of ψ_v̂(g)=log∥gv∥ (see the statement and proof outline in Sections 2 and 7, together with the spectral theory developed in Section 6 ). The candidate solution establishes the same conclusion by a coupling-and-contraction route, deriving a recursion for projective angles and a telescoping sum bound. Aside from a minor constant/exponent slip (a factor r^{1−α} should replace r^{α−1} in the final normalization) and an over-terse justification of the expectation-to-exponent limit, the argument is logically sound and compatible with the paper’s hypotheses. Hence, both are correct, but they use substantially different proof strategies.

Referee report (LaTeX)

\textbf{Recommendation:} minor revisions

\textbf{Journal Tier:} strong field

\textbf{Justification:}

The paper extends Hölder regularity of Lyapunov exponents to non-invertible and non-compact matrix cocycles under natural spectral and irreducibility conditions, with a careful Wasserstein framework. The spectral-operator approach is robust and yields further consequences (e.g., strong mixing and large deviations). Clarity is high overall, though a few technical steps (truncation/tail handling and parameter ranges) could be streamlined and constants made more explicit. The contribution is valuable for the random matrix and dynamical systems communities.