Eigenvectors of the EM stress-energy tensor

[Creedence]

TL;DR

What do they mean?

My question is that what is the physical meaning of the EM stress-energy tensor's eigenvectors?
Thanks for the answers - Robert

 

[Paul Colby]

I would think an eigenvector of a stress energy tensor to be that directed area for which the energy-momentum passing through is collinear with the area vector but I'm just guessing.

 

[vanhees71]

Isn't this rather provided by the eigenvectors of the $3 \times 3$ stress tensor alone and not the energy-momentum-stress tensor?