On geometric properties of passive random advection

Abstract

We study geometric properties of a random Gaussian short-time correlated velocity field by considering statistics of a passively advected metric tensor. That describes universal properties of fluctuations of tensor objects frozen into the fluid and passively advected by it. The problem of one-point statistics of co- and contravariant tensors is solved exactly, provided the advected fields do not reach dissipative scales, which would break the symmetry of the problem. Asymptotic in time duality of the problem is established, which in the three-dimensional case relates the probabilities of the volume deformations into "tubes" and into "sheets".