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2112.14562

POLYNOMIAL EFFECTIVE DENSITY IN QUOTIENTS OF H3 AND H2 × H2

E. Lindenstrauss, A. Mohammadi

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

Audit review

The paper’s main theorem exactly states the quantitative dichotomy for P-orbits in X = G/Γ (G = SL2(C) or SL2(R)×SL2(R)) with the parameters A, κ1, C1 and the alternative involving a nearby periodic H-orbit, and it gives a complete proof based on non-divergence, a projection/incidence step, spectral gap for the ambient space, and an effective closing lemma. By contrast, the model’s solution hinges on a global quantitative mean/pointwise ergodic theorem for the H-action along well-rounded P-averages with a polynomial rate uniform away from small periodic orbits; such a tool does not exist in the requisite generality here and is precisely the gap the paper fills by a different route. The model also conflates a K-thickening in G with sets lying inside H, and it normalizes exponents post hoc. Hence the paper’s argument is correct and novel, while the model’s proof relies on unproven assumptions.

Referee report (LaTeX)

\textbf{Recommendation:} minor revisions

\textbf{Journal Tier:} top field-leading

\textbf{Justification:}

The paper establishes the first polynomial-rate effective density theorem for general P-orbits in arithmetic quotients of SL2(C) and SL2(R)×SL2(R), beyond the horospherical setting. The proof innovatively combines a Margulis function and random-walk technique with a projection theorem and an effective closing lemma, all underpinned by ambient spectral gap. The results are significant and timely; clarity is generally high, though a few expository refinements would help readers track constants and parameter dependencies across sections.