#### haushofer

Science Advisor

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The book of d'Inverno speaks about turning the question into an eigenvalue problem, in which he turns the eigenvectors in a tetrad. I don't understand this also.....and least but not last, I look for a derivation of the dominant energy condition of Hawking and Ellis ( maybe they use the way which I described earlier? )

If someone could help me, I would be very pleased! I'm busy right now with a little research in cosmology and the cosmological constant, and I'm a little stuck right now :)