The relativistic redshift for a particle is given by





where
is the rest wavelength. From the relativistic Doppler shift

So, for







Since, to first-order approximation

using

gives



The time derivative of z is

where a is the expansion parameter and H is Hubble constant. In the Einstein-de Sitter cosmological model, the derivative is



In terms of the expansion parameter,



But

so






(1)
where


(2)
So, for








(3)
Since, to first-order approximation

(4)
using

(5)
gives

(6)

(7)

(8)
The time derivative of z is

(9)
where a is the expansion parameter and H is Hubble constant. In the Einstein-de Sitter cosmological model, the derivative is

(10)

(11)

(12)
In terms of the expansion parameter,

(13)

(14)

(15)
But

(16)
so

(17)
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