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    Definition of the Einstein Tensor

    I provide an answer this question in my page General Relativity : the Einstein field equation. I just wrote this page in the last days; see also the cosmology page linked there for a more intuitive, less formal description. This explanation is quite brief and assumes some familiarity with tensor...
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    Energy in GR - side question

    Energy in GR can no more be described as a precise quantity simply obtained by integrating some explicit field along the space-like 3D surface we consider. This does not mean that there is no conservation of energy. But it takes a more subtle, complex form. In particular we can roughly define...
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    Details of Stress-Energy-Momentum Tensor

    These descriptions are all true, so that a logical consequence of them is that the energy flux happens to equal the momentum density (*c2), while these are 2 different concepts. Usual conventions on tensors assume c=1 so that "mass" and energy are the same. If we don't put c=1, as the...