Non-uniqueness of weak solutions to the Navier-Stokes equations in R^3

TL;DR

This paper demonstrates the non-uniqueness of weak solutions to the Navier-Stokes equations in the entire three-dimensional space, extending previous results from periodic domains using convex integration and localized correction techniques.

Contribution

It extends non-uniqueness results for Navier-Stokes solutions from periodic domains to the whole space R^3 using a novel iterative scheme with localized corrections.

Findings

Existence of infinitely many weak solutions dissipating energy in bounded domains.

Non-uniqueness of solutions in R^3 with finite kinetic energy.

Instability of Navier-Stokes near Couette flow in L2(R^3).

Abstract

To our knowledge, the convex integration method has been widely applied to the study of non-uniqueness of solutions to the Naiver-Stokes equations in the periodic region, but there are few works on applying this method to the corresponding problems in the whole space or other regions. In this paper, we prove that weak solutions of the Navier-Stokes equations are not unique in the class of weak solutions with finite kinetic energy in the whole space, which extends the non uniqueness result for the Navier-Stokes equations on torus T3in the groundbreaking work (Buckmaster and Vicol, Ann. of Math., 189 (2019), pp.101-144) to R3. The critical ingredients of the proof include developing an iterative scheme in which the approximation solution is refined by decomposing it into local and non-local parts. For the non-local part, we introduce the localized corrector which plays a crucial role in balancing the compact support of the Reynolds stress error with the non-compact support of the solution. As applications of this argument, we first prove that there exist infinitely many weak solutions that dissipate the kinetic energy in smooth bounded domain. Moreover, we show the instability of the Navier-Stokes equations near Couette flow in L2(R3).