There is no boundary. On Feb 14, 2012 5:47 PM, "Mohammad Mirzadeh" <mirzadeh at gmail.com> wrote:
> What do you set on the sphere? If you impose a Dirichlet BC that makes it > nonsingular > > Mohammad > On Feb 14, 2012 7:27 AM, "Jed Brown" <jedbrown at mcs.anl.gov> wrote: > >> 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/bb91e2d5/attachment.htm>
