Expansionsfaktorn
Expansionsfaktorn, or expansion factor, is a dimensionless function a(t) that describes the expansion of space in cosmological models. It is the scale factor in the Friedmann-Lemaître-Robertson-Walker metric and relates the proper distance between comoving points by D(t) = a(t) χ, where χ is the comoving distance. The function is typically normalized so that a(t0) = 1 at the present time t0.
The Hubble parameter is defined as H(t) = ȧ(t) / a(t), describing the rate of expansion. For distant
The expansion factor evolves according to the Friedmann equations, which connect ȧ, a, and the energy content
Significance: the expansion factor encodes the history of cosmic expansion; it is not a physical velocity of