Optimal error estimates for the pseudostress formulation of the Navier-Stokes equations

In this paper, we prove optimal a priori error estimates for the pseudostress-velocity mixed finite element formulation of the incompressible Navier-Stokes equations, thus improve the result of Cai et al. (SINUM 2010). This is achieved by applying Petrov-Galerkin type Brezzi-Rappaz-Raviart theory.