Uniform-in-diffusivity mixing by shear flows: stochastic and dynamical perspectives

Kyle L. Liss; Kunhui Luan

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arXiv · 2603.09238

Uniform-in-diffusivity mixing by shear flows: stochastic and dynamical perspectives

Kyle L. Liss·Kunhui Luan

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Abstract

We study passive scalar mixing by parallel shear flows in the presence of weak molecular diffusion. We recover the sharp uniform-in-diffusivity mixing rate for shear flows with finitely many critical points, recently proven in [1]. Our approach is based on the stochastic representation formula of the associated advection-diffusion equation and yields two short proofs. The first uses a stochastic integration-by-parts argument and gives optimal mixing under the weakest regularity assumption required in the zero-diffusion case, answering Question II in [1, Section 4]. The second adopts a dynamical systems perspective and provides a proof of shear-induced mixing that, to our knowledge, is new even in the zero-diffusivity setting.

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Kyle L. Liss, Kunhui Luan. 2026-03-10. Uniform-in-diffusivity mixing by shear flows: stochastic and dynamical perspectives. https://arxiv.org/abs/2603.09238

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