LOCAL MULTILEVEL METHODS FOR ADAPTIVE FINITE ELEMENT METHODS FOR NONSYMMETRIC AND INDEFINITE ELLIPTIC BOUNDARY VALUE PROBLEMS

In this paper, we propose some local multilevel algorithms for solving linear systems arising from adaptive finite element approximations of nonsymmetric and indefinite elliptic boundary value problems. Two types of local smoothers are constructed. One is based on the original nonsymmetric problems, and the other is defined in terms of the associated symmetric problems. It is shown that the local multilevel methods for the nonsymmetric and indefinite elliptic boundary value problems are optimal, which means that the convergence rates of the local multilevel methods are independent of mesh sizes and mesh levels provided that the coarsest grid is sufficiently fine. Numerical experiments are reported to confirm our theory.