Interpreting Complex Eigenvalues in Comsol Analysis

[ra123]

Hey,
Im working with Comsol and doing some eigenvalue analysis.
Why is sometimes the eigenvalues are complex numbers and not real number frequencies?
How should I interpret these complex eigenvalues?
Thanks

 

[FredGarvin]

They are sometimes imaginary because, at the heart of eigenvalue solving (the ones that I know of anyways) is solving a polynomial for it's roots. For example, finding the principal stresses in a 3x3 stress tensor is an eigenvalue problem. In that you are solving for the roots of a third order polynomial.

 

[ra123]

okaay great, so can i just take the absolute value as the eigenfrequency to work with?