On Tue, Feb 14, 2012 at 09:20, Thomas Witkowski < thomas.witkowski at tu-dresden.de> wrote:
> I discretize the Laplace operator (using finite element) on the unit > square equipped with periodic boundary conditions on all four edges. Is it > correct that the null space is still constant? I wounder, because when I > run the same code on a sphere (so a 2D surface embedded in 3D), the > resulting matrix is non-singular. I thought, that both cases should be > somehow equal with respect to the null space? > The continuum operators for both cases have a constant null space, so if either is nonsingular in your finite element code, it's a discretization problem. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20120214/a819d789/attachment.htm>
