fenics team mailing list archive

[Gideon Simpson <grs2103@xxxxxxxxxxxx>]

Something I discovered that I'm hoping someone will clarify is the  
following.

Let A be the matrix associated with a Finite Element formulation of  
Poisson's equation, as in the example in the demo directory.  If one  
exams the eigenvalues of A before the application of the BC's, there  
is a zero eigenvalue, while afterwards, there is no such troublemaker.

Thinking of A in terms of its associated weak form, I fully expected  
A to be a positive definite, symmetric matrix.  This is not the case.


-gideon