arXiv:2507.23731v2

Fourier decay of equilibrium states and the Fibonacci Hamiltonian

Gaétan Leclerc

math.DSmath-phmath.SP37A4637D3537A2537D4581Q35

Abstract

We show power Fourier decay for equilibrium states of nonlinear, area preserving, smooth Axiom-A diffeomorphisms on surfaces. This implies positivity of the lower Fourier dimension for self-conformal measures under C1+C^{1+} iterated function systems that are factors of hyperbolic diffeomorphisms, which is the first result of this kind in this low-regularity setting. To do so, we use the sum-product phenomenon to reduce Fourier decay to the study of a temporal distance function for a well chosen suspension flow, behaving like a 3-dimensional Axiom A flow, whose mixing properties reflects the nonlinearity of our base dynamics. We then generalize in an Axiom A setting the methods of Tsujii-Zhang, dealing with exponential mixing of three-dimensional Anosov flows arXiv:2006.04293. The nonlinearity condition is generic and can be checked in concrete contexts. To illustrate the applications, we prove two corollaries. We first establish a spectral gap, proving exponential mixing for generic circle extensions over hyperbolic maps on surfaces. As a second application, we prove power Fourier decay for the density of states measure of the Fibonacci Hamiltonian. This implies phase-averaged escape-of-mass estimates, which is the first result of this type in a quasicrystal.

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Audited against arXiv v2

Not a correctness certificate. A “Correct” result may include yellow typos or minor formal corrections that do not affect substantive soundness. It means this audit found no unresolved substantive error under the stated criteria; it does not replace expert scrutiny or formal verification.

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Detailed mathematical audit

Generated August 18, 2026
01Statements2 reported findingsCorrect

The power Fourier decay theorem for nonlinear area-preserving Axiom-A surface dynamics and its Fibonacci-Hamiltonian and circle-extension applications are correct outside the explicitly stated discrete exceptional set.

Theorems 1.1, 1.3, 1.5–1.6, and 1.10–1.11Correct

Nonlinearity gives Fourier decay and the stated applications

Pages 3–13 and Sections 3–6 · arXiv:2507.23731v2

The quantitative nonlinearity condition gives polynomial nonconcentration of temporal distance. Regular-word decompositions and the sum-product theorem convert this into uniform oscillatory-integral decay for equilibrium states. For the trace map, analyticity of the Anosov cocycle makes its zero set closed and discrete after a nonzero small-coupling computation; stable holonomy transfers the resulting decay to the density of states. The phase-averaged quantum and generic circle-extension consequences then follow from the stated Fourier and Dolgopyat estimates.

Full paper, version 2
Theorems 1.5–1.6 and spectral applicationsCorrect

Fourier decay criteria feed correctly into the Fibonacci density-of-states conclusions

Pages 8–14 and Sections 5–6 · arXiv:2507.23731v2

Stable/unstable nonintegrability yields decay for equilibrium projections under the stated Axiom A hypotheses. The trace-map coding then identifies the density-of-states measure with such a projection on the relevant hyperbolic set, so the convolution and exceptional-coupling conclusions use exactly the established decay exponent.

02Proofs2 reported findingsCorrect

The symbolic reduction, nonconcentration, sum-product, temporal-distance, trace-map, and spectral applications are correct and complete.

Sections 3–6 and Appendices B–DCorrect and complete

The nonlinear Fourier-decay mechanism closes at every scale

Pages 21–78 · Sections 3–6 and Appendices B–D · arXiv:2507.23731v2

Large deviations remove only exponentially small families of irregular words, distortion is uniform on regular cylinders, and the temporal-distance templates satisfy the nonconcentration exponents needed by the sum-product input. The trace-map computation verifies nonvanishing before analyticity is used, and the extended RAGE argument applies Fourier decay after the phase average with the required domination.

Sections 4–6Correct and complete

Nonconcentration, sum-product decay, and trace-map transfer form a complete chain

Pages 30–62 · arXiv:2507.23731v2

Cylinder distortion and temporal-distance estimates give uniform projective nonconcentration, after which the additive-combinatorial estimate controls the Fourier transform blockwise. The Markov coding and holonomy maps preserve the needed regularity, and the final trace-map identification transfers the bound to the density-of-states measure.

03Novelty0 reported findingsNo non-novelty findings

No non-novelty findings.

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Paper
arXiv:2507.23731v2
Authors listed
Gaétan Leclerc
Audit date
August 18, 2026
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