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Cosmography: Cosmology without the Einstein equations. (English) Zbl 1080.83026

Summary: How much of modern cosmology is really cosmography? How much of modern cosmology is independent of the Einstein equations? (Independent of the Friedmann equations?) These questions are becoming increasingly germane-as the models cosmologists use for the stress-energy content of the universe become increasingly baroque, it behaves us to step back a little and carefully disentangle cosmological kinematics from cosmological dynamics. The use of basic symmetry principles (such as the cosmological principle) permits us to do a considerable amount, without ever having to address the vexatious issues of just how much “dark energy”, “dark matter”, “quintessence”, and/or “phantom matter” is needed in order to satisfy the Einstein equations. This is the sub-sector of cosmology that Weinberg refers to as “cosmography”, and in this article I will explore the extent to which cosmography is sufficient for analyzing the Hubble law and so describing many of the features of the universe around us.

MSC:

83F05 Relativistic cosmology
83C55 Macroscopic interaction of the gravitational field with matter (hydrodynamics, etc.)
85A40 Astrophysical cosmology

References:

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