A MULTILEVEL ALGORITHM FOR MIXED PROBLEMS

A multilevel algorithm is described for the numerical solution of symmetric indefinite problems which arise, e. g. from mixed finite element approximation of the Stokes equation. The main difficulty, besides the indefiniteness, is the lack of regularity of the solution of the corresponding continuous problem. This is overcome by introducing a scale of mesh-dependent norms. The convergence rate of the described algorithm is bounded independently of the meshsize.