2103.00645
Erdős–Rényi laws for exponentially and polynomially mixing dynamical systems
Nicolai Haydn, Matthew Nicol
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 an Erdős–Rényi limit law at the logarithmic window length L_n = ⌊(ln n)/I(α)⌋ for Hölder observables on systems modeled by Young towers with exponential tails, proving that max_{0≤j≤n−L_n} S_{L_n}(T^j x)/L_n → α almost surely (see Proposition 4.1 for the reduction and Theorem 5.1 for the main result, with LDP assumptions and the tower-based proof strategy) . The paper’s argument proves the upper bound from the LDP alone and the lower bound via a blocking argument on the quotient tower that leverages decay of correlations using a symbolic metric and Lipschitz approximations to indicator functions, rather than α-mixing . The model’s solution also derives the same limit: the upper bound via a union bound plus the LDP (matching the paper’s Proposition 4.1(a)), and the lower bound via separated-window testing combined with exponential α-mixing and Borel–Cantelli. This is a different proof route. Two minor issues in the model writeup are: (i) a small misalignment in the “bridging” step for the upper bound when handling n between exp(m I(α)) and exp((m+1) I(α))—which is easily fixed by applying the union bound up to n_{m+1} for window length m—and (ii) for the lower bound, one must either run the separated-window argument for both lengths m and m+1 or use boundedness of ϕ to transfer an m-exceedance to an (m+1)-exceedance. With these standard fixes, the model proof is correct. Overall, the paper’s proof is complete and correct, and the model provides a correct alternative proof under standard α-mixing that holds for Young towers with exponential tails (citing external results).
Referee report (LaTeX)
\textbf{Recommendation:} minor revisions
\textbf{Journal Tier:} strong field
\textbf{Justification:}
The paper proves an optimal Erdős–Rényi law at the logarithmic scale for a large class of nonuniformly hyperbolic systems modeled by Young towers with exponential tails. The use of a symbolic metric and quotient-tower correlation decay to control indicator approximations is technically clean and avoids reliance on mixing coefficients. The results match the i.i.d. benchmark and are of clear interest to specialists. Minor clarifications would further improve readability.