cosmic scale factor

cosmic scale factor

Symbol: R. A measure of the size of the Universe as a function of time. R is related to the redshift parameter, z, by
1 + z = R (t 0 )/R (t 1 )

where t 0 is the present time and t 1 is the time at emission of the radiation. The quantity (1 + z) thus gives the factor by which the Universe has expanded in size between the time t 1 and the present, t 0. The proper distance between the origin and a point at a comoving coordinate r (i.e. in a system expanding with the Universe) is given by the product of R (t) and sin–1r, r, or sinh–1r depending on whether the Universe is closed, Euclidean, or open, respectively. R is also related to the Hubble constant H 0 :

H 0 = R –1(dR /dt )

References in periodicals archive ?
Our model however, is bound to a main restriction: for physical reasons, it provides a solution which holds only for the existence of the cosmic scale factor, within the Godel metric.
In the full RW model F(t) is called the cosmic scale factor which varies with the (cosmic) proper time t of the whole space.