Very weak solutions for the stationary Stokes equations

Abstract

The concept of very weak solution introduced by Giga (1981) for the stationary Stokes equations has been intensively studied in the last years for the stationary Navier–Stokes equations. We give here a new and simpler proof of the existence of very weak solution for the stationary Navier–Stokes equations, based on density arguments and an adequate functional framework in order to define more rigorously the traces of non-regular vector fields. We also obtain regularity results in fractional Sobolev spaces. All these results are obtained in the case of a bounded open set, connected of class C 1 , 1 of R 3 and can be extended to the Laplace's equation and to other dimensions.