Norm inflation for generalized Navier-Stokes equations

Abstract

We consider the incompressible Navier-Stokes equation with a fractional power $\alpha\in[1,\infty)$ of the Laplacian in the three dimensional case. We prove the existence of a smooth solution with arbitrarily small in $\dot{B}_{\infty,p}^{-\alpha}$ ($2 0$ in arbitrarily small time. This extends the result of Bourgain and Pavlovic for the classical Navier-Stokes equation which utilizes the fact that the energy transfer to low modes increases norms with negative smoothness indexes. It is remarkable that the space $\dot{B}_{\infty,\infty}^{-\alpha}$ is supercritical for $\alpha >1$. Moreover, the norm inflation occurs even in the case $\alpha \geq 5/4$ where the global regularity is known.