Sharp nonuniqueness for the forced 2D Navier-Stokes and dissipative SQG equations

Abstract

We prove a sharp nonuniqueness result for the forced generalized SQG equation. First, this yields nonunique ${\dot{H}}^s$- energy solutions below the Miura-Ju class. In particular, this shows that the solutions constructed by Resnick and Marchand for the dissipative SQG equation are not necessarily unique. Second, this establishes nonuniqueness below the Ladyzhenskaya-Prodi-Serrin class for the 2D Navier-Stokes equation, as well as below the Constantin-Wu and Dong-Chen-Zhao-Liu classes for the dissipative SQG equation.