MULTIGRID TECHNIQUES FOR NONLINEAR EIGENVALUE PROBLEMS; SOLUTIONS OF A NONLINEAR SCHRODINGER EIGENVALUE PROBLEM IN 2D AND 3D

This paper presents MG techniques for nonlinear EP and emphasizes an MG algorithm for a nonlinear Schrodinger EP. The algorithm overcomes the mentioned difficulties combining the following techniques: an MG projection coupled with backrotations for separation of solutions and treatment of difficulties related to clusters of close and equal eigenvalues; MG subspace continuation techniques for the treatment of the nonlinearity; an MG simultaneous treatment of the eigenvectors at the same time with the nonlinearity and with the global constraints. The simultaneous MG techniques reduce the large number of selfconsistent iterations to only a few or one MG simultaneous iteration and keep the solutions in a right neighborhood where the algorithm converges fast.