I would like to get a mathematically precise formulation of the Ehlers-Geren-Sachs theorem. I have heard that this theorem roughly tells us that the universe in total is described by a FLRW metric if there exists a set of fundamental observers, with respect to whom all observable properties of the Universe are isotropic. But this in my eyes is not a mathematically precise statement and I would like to see a rigorous mathematical theorem about differential-geometric properties of spacetimes. Can you give me a reference, where I can find it?(adsbygoogle = window.adsbygoogle || []).push({});

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# Mathematically precise formulation of Ehlers-Geren-Sachs theorem

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