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2210.15480

L1-FLAT POLYNOMIALS AND SIMPLE LEBESGUE SPECTRUM FOR CONSERVATIVE MAPS EXIST: A SIMPLE PROOF.

el HOUCEIN el ABDALAOUI

correctmedium confidence
Category
Not specified
Journal tier
Specialist/Solid
Processed
Sep 28, 2025, 12:56 AM

Audit review

The paper proves L^α-flatness (0<α<2) for 0–1 analytic polynomials built from Singer sets via a careful Marcinkiewicz–Zygmund interpolation argument that uses only the values of the auxiliary polynomial Q_q on q-th roots of unity, where Q_q(1)=|S|-1 and Q_q(z_r)=-1/|S| for r=1,...,q-1, then controls the L^α norms and passes to α≤1 by monotonicity (see (2.5), (2.12)–(2.19) in the paper) . The model’s core step asserts the global identity |P_q(z)|^2 = 1 + r^{-1}∑_{x=1}^{q-1} z^x for all z on the circle; that identity holds only at q-th roots of unity and is false for general z. Without the paper’s interpolation step (or a correct inequality bound), the model’s reduction to Dirichlet kernel norms is invalid. The real-line windowed flatness and the spectral constructions (rank-one map/flow, generalized Riesz products) in the paper are standard and correctly executed (Fejér kernel step and rank-one spectral formula) . Hence: paper correct; model’s argument has a crucial flaw.

Referee report (LaTeX)

\textbf{Recommendation:} minor revisions

\textbf{Journal Tier:} specialist/solid

\textbf{Justification:}

The manuscript offers a short, coherent construction of L\^1-flat 0–1 polynomials using Singer sets and a clean interpolation argument, and applies standard generalized Riesz-product and rank-one machinery to produce conservative systems and flows with simple Lebesgue spectrum. The proofs are correct and well-motivated. Minor clarifications (e.g., explicitly restricting certain identities to evaluations at q-th roots and adding brief reminders for the spectral product criteria) would further improve readability for non-specialists.