Lower bounds on the top Lyapunov exponent for linear PDEs driven by the 2D stochastic Navier-Stokes equations

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Main Authors: Hairer, Martin, Punshon-Smith, Sam, Rosati, Tommaso, Yi, Jaeyun
Format: Preprint
Published: 2024
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author Hairer, Martin
Punshon-Smith, Sam
Rosati, Tommaso
Yi, Jaeyun
author_facet Hairer, Martin
Punshon-Smith, Sam
Rosati, Tommaso
Yi, Jaeyun
contents We consider the top Lyapunov exponent associated to the advection-diffusion and linearised Navier-Stokes equations on the two-dimensional torus. The velocity field is given by the stochastic Navier-Stokes equations driven by a non-degenerate white-in-time noise with a power-law correlation structure. We show that the top Lyapunov exponent is bounded from below by a negative power of the diffusion parameter. This partially answers a conjecture of Doering and Miles and provides a first lower bound on the Batchelor scale in terms of the diffusivity. The proof relies on a robust analysis of the projective process associated to the linear equation, through its spectral median dynamics. We introduce a probabilistic argument to show that high-frequency states for the projective process are unstable under stochastic perturbations, leading to a Lyapunov drift condition and quantitative-in-diffusivity estimates.
format Preprint
id arxiv_https___arxiv_org_abs_2411_10419
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Lower bounds on the top Lyapunov exponent for linear PDEs driven by the 2D stochastic Navier-Stokes equations
Hairer, Martin
Punshon-Smith, Sam
Rosati, Tommaso
Yi, Jaeyun
Probability
Analysis of PDEs
Dynamical Systems
60H15, 35Q35, 37H15, 37L30
We consider the top Lyapunov exponent associated to the advection-diffusion and linearised Navier-Stokes equations on the two-dimensional torus. The velocity field is given by the stochastic Navier-Stokes equations driven by a non-degenerate white-in-time noise with a power-law correlation structure. We show that the top Lyapunov exponent is bounded from below by a negative power of the diffusion parameter. This partially answers a conjecture of Doering and Miles and provides a first lower bound on the Batchelor scale in terms of the diffusivity. The proof relies on a robust analysis of the projective process associated to the linear equation, through its spectral median dynamics. We introduce a probabilistic argument to show that high-frequency states for the projective process are unstable under stochastic perturbations, leading to a Lyapunov drift condition and quantitative-in-diffusivity estimates.
title Lower bounds on the top Lyapunov exponent for linear PDEs driven by the 2D stochastic Navier-Stokes equations
topic Probability
Analysis of PDEs
Dynamical Systems
60H15, 35Q35, 37H15, 37L30
url https://arxiv.org/abs/2411.10419