Super-diffusivity in a shear flow model from perpetual homogenization

Abstract

This paper is concerned with the asymptotic behavior solutions of stochastic differential equations dy_t =dω_ t −∇Γ(y_t ) dt, y_0=0 and d=2. Γ is a 2 x 2 skew-symmetric matrix associated to a shear flow characterized by an infinite number of spatial scales Γ_(12) = −Γ_(21) = h(x_1), with h(x_1) = ∑_(n =0)^∞γ_n h^n (x_1/R_n ), where h^n are smooth functions of period 1, h^n (0)=0, γ_ n and R_n grow exponentially fast with n. We can show that y_t has an anomalous fast behavior (?[|y_t |^2]∼t^(1+ν) with ν > 0) and obtain quantitative estimates on the anomaly using and developing the tools of homogenization.