[1] 
J. Garcke and M. Griebel.
On the computation of the eigenproblems of hydrogen and helium in
strong magnetic and electric fields with the sparse grid combination
technique.
Journal of Computational Physics, 165(2):694716, 2000. [ bib  DOI  http  .ps.gz 1  .pdf 1 ] We introduce the combination technique for the numerical solution of deigenproblems on sparse grids. Here, O(d ·(logN)^{d1}) different problems, each of size O(N), have to be solved independently. This is in contrast to the one problem of size O(N^{d}) for a conventional finite element discretization, where N denotes the number of grid points in one coordinate direction. Therefore, also higher dimensional eigenvalue problems can be treated by our sparse grid combination approach. We apply this method to solve the threedimensional Schrödinger equation for hydrogen (one electron problem) and the sixdimensional Schrödinger equation for helium (two electron problem) in strong magnetic and electric fields.
