Multi-locality and fusion rules on the generalized structure functions in two-dimensional and three-dimensional Navier-Stokes turbulence

TL;DR

This paper extends the proof of locality in turbulence theory to multiple nonlinear interactions, demonstrating that fusion rules imply both locality and multilocality in various cascades of 2D and 3D Navier-Stokes turbulence.

Contribution

It introduces the concept of multilocality and develops a new fusion rule leveraging rotational symmetry, advancing the understanding of non-perturbative locality in turbulence.

Findings

Fusion rules imply locality and multilocality in turbulence cascades.

Locality holds in both IR and UV limits for all orders of structure functions.

The results apply to both 2D and 3D Navier-Stokes turbulence cascades.

Abstract

Using the fusion rules hypothesis for three-dimensional and two-dimensional Navier-Stokes turbulence, we generalize a previous non-perturbative locality proof to multiple applications of the nonlinear interactions operator on generalized structure functions of velocity differences. We shall call this generalization of non-perturbative locality to multiple applications of the nonlinear interactions operator "multilocality". The resulting cross-terms pose a new challenge requiring a new argument and the introduction of a new fusion rule that takes advantage of rotational symmetry. Our main result is that the fusion rules hypothesis implies both locality and multilocality in both the IR and UV limits for the downscale energy cascade of three-dimensional Navier-Stokes turbulence and the downscale enstrophy cascade and inverse energy cascade of two-dimensional Navier-Stokes turbulence. We stress that these claims relate to non-perturbative locality of generalized structure functions on all orders, and not the term by term perturbative locality of diagrammatic theories or closure models that involve only two-point correlation and response functions.