Smoothing techniques and computation of invariant subspaces of elliptic operators Original Research Article

We propose a generalized Krylov subspace method for computing the invariant subspace associated with the smallest eigenvalues of an elliptic operator. The success of the method relies upon a smoothing operator whose main purposes is to enhance the components of the smallest eigenvalues while dumping those of the largest ones. We show numerically that multigrid techniques can be used to construct an efficient smoothing operator.