El 04/02/2015, a las 19:32, Andrew Spott escribió: > When I compute the eigenvectors of a real symmetric matrix, I’m getting > eigenvectors that are rotated by approximately pi/4 in the complex plane. So > what could be purely real eigenvectors have some overall phase factor. > > Why is that? And is there a way to prevent this overall phase factor? > > -Andrew >
Eigenvectors are normalized to have 2-norm equal to one. Complex eigenvectors may be scaled by any complex scalar of modulus 1. When computing eigenvectors of a real symmetric matrix in complex arithmetic, the solver cannot control this because the matrix is not checked to be real. Since you know it is real, you could do a postprocessing that scales the eigenvectors as you wish. This is done in function FixSign() in this example: http://slepc.upv.es/documentation/current/src/nep/examples/tutorials/ex20.c.html Jose
