Comoving volume

The comoving volume VC is the volume in which the number densities of non-evolving objects locked into the Hubble flow are constant with redshift. It is the proper volume times three factors of the relative scale factor from the present epoch to the time at redshift z, or (1 + z)3. It can be thought of as the cosmological volume with the expansion of the Universe factored out, i.e. the comoving volume defined by a fixed set of objects remains constant, and is useful in cosmological calculations.

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