2504.09731
LYAPUNOV SPECTRUM VIA BOUNDARY THEORY I - FRAMEWORK
Uri Bader, Alex Furman
incompletemedium confidence
- Category
- math.DS
- Journal tier
- Strong Field
- Processed
- Sep 28, 2025, 12:56 AM
- arXiv Links
- Abstract ↗PDF ↗
Audit review
The paper establishes (1) simplicity (ΛF ∈ a++) for Zariski-dense representations and (2) continuity of Λ under uniform integrability with complete, self-contained proofs in the Apafic Greg framework, including an explicit Iwasawa-cocycle formula and a tight continuity argument (Proposition 6.5 and the convergence estimate (6.11)) . However, for (3) positivity of the drift, the case where the Zariski closure H of ρ(Γ) is disconnected relies on a “cocycle trick” explicitly marked ‘to be justified in the updated version with cocycles,’ leaving a gap in the present manuscript . The model’s solution captures the right high-level strategy and gives correct conclusions for (1)–(2) in spirit, but it glosses over key hypotheses: it appeals to continuity-of-stationary-measures results that typically require stronger (e.g., exponential) moment bounds than the paper assumes, and it asserts exact functoriality of the Cartan projection under homomorphisms in (3), which is too strong as stated. Hence both are incomplete: the paper on (3), the model on technical hypotheses and rigor in (2)–(3).
Referee report (LaTeX)
\textbf{Recommendation:} major revisions \textbf{Journal Tier:} strong field \textbf{Justification:} This manuscript introduces a robust boundary-theoretic framework (Apafic Gregs) yielding simplicity and continuity of Lyapunov spectra well beyond i.i.d. products. The proofs of (1) and (2) are complete and convincing, recovering classical results and extending them with minimal moment assumptions. However, Theorem A.(3) currently contains an explicit gap for the disconnected Zariski-closure case, deferred to a future update; this must be addressed for publication. Clarity and organization are good, and the results are significant.