arXiv:2606.11055v1

Exponential mixing and enhanced dissipation on the unit sphere with Rossby-Haurwitz flows

Augusto Del Zotto, Marc Nualart

math.APmath.DSphysics.flu-dyn35Q4937H0537A2576F25

Abstract

We exhibit a family of smooth incompressible velocity fields on the two-dimensional unit sphere such that the time evolution of any mean-free initial data passively advected by any of them is mixed exponentially fast. In the presence of molecular diffusivity, we show that the solution to the associated advection-diffusion equation experiences enhanced dissipation with optimal decay rates. Each member of this family is an alternating combination of two Rossby-Haurwitz flows with random amplitudes and constitutes a spherical analogue to the sine shear-alternating example of Pierrehumbert.

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Audited against arXiv v1

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 uniform-in-diffusivity exponential correlation decay, passive-scalar mixing, and optimal logarithmic enhanced-dissipation conclusions are correct for every pair of non-parallel axes under the stated random-amplitude model.

Theorem 1.1 and Corollary 1.2Correct

The alternating Rossby–Haurwitz flow mixes exponentially almost surely

Pages 4–6 and Sections 2–12 · arXiv:2606.11055v1

The one-point, projective, and inviscid two-point chains satisfy the required irreducibility, small-set, and drift conditions; the projective argument also gives a positive top Lyapunov exponent. The stochastic two-point drift and minorization are uniform for small diffusivity. Quantitative Harris theory then gives the correlation estimate with a random prefactor whose moments are uniform in the diffusivity, and Sobolev duality yields Corollary 1.2.

Corollary 1.3Correct

The enhanced-dissipation rate has the claimed optimal logarithmic scale

Page 5 and pages 77–78 · enhanced-dissipation corollary and proof · arXiv:2606.11055v1

Combining uniform exponential mixing with energy monotonicity gives a contraction after a time proportional to log(1/κ)\log(1/\kappa). Iteration produces the random rate μ(κ)\mu(\kappa), and the uniform second moment of the mixing prefactor gives the displayed high-probability lower bound. The deterministic upper bound and the probability estimate together place μ(κ)log(1/κ)\mu(\kappa)\log(1/\kappa) in the announced interval.

02Proofs2 reported findingsCorrect

The Lie-algebra rank calculations, fixed-set drift functions, stochastic stability estimates, and uniform Harris theorem verify every input required for mixing and enhanced dissipation.

Sections 4–8Correct and complete

The inviscid geometric-ergodicity and Lyapunov-exponent arguments cover non-parallel axes

Lie-algebra rank, one-point, projective, and two-point analyses · arXiv:2606.11055v1

The commutator computations give full rank at explicit points and the submersion criterion supplies open small sets. The fixed points and other symmetry sets are identified before the phase spaces are punctured, and the drift functions control every approach to those sets. Furstenberg's criterion is applied only after projective irreducibility is proved.

Sections 9–12Correct and complete

The stochastic two-point estimates are uniform in small diffusivity

Stochastic stability, drift construction, and Proposition 12.6 · arXiv:2606.11055v1

The inner-core, annular, and outer regimes cover neighborhoods of every inviscid fixed set and give one global Lyapunov–Foster inequality. Compact reachability and the local submersion estimate are then transferred to the noisy chain with constants uniform in κ\kappa. Proposition 12.6 matches the exact quantitative Harris hypotheses quoted in Section 2.

03Novelty0 reported findingsNo non-novelty findings

No non-novelty findings.

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Paper
arXiv:2606.11055v1
Authors listed
Augusto Del Zotto, Marc Nualart
Audit date
August 18, 2026
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