0
$\begingroup$

I am trying to calculate the redshift drift where its written as

$$\frac{dz}{dt} = (1+z)H_0 - H \tag{1}$$

We also know that $$1+z = a(t_o) / a(t_e) \tag{2}$$

and $$H_0 = \frac{\dot{a}(t_0)}{a(t_0)}$$

$$H = \frac{\dot{a}(t_e)}{a(t_e)}$$

$\endgroup$
3
  • $\begingroup$ Related question: physics.stackexchange.com/q/400386 $\endgroup$
    – D. Halsey
    Sep 30, 2020 at 12:45
  • $\begingroup$ Layla, can you specify your problem? If you know the scale factors then the redshift is given by your equation (2). $\endgroup$
    – psm
    Sep 30, 2020 at 15:13
  • $\begingroup$ @psm What information do you need ? $\endgroup$
    – seVenVo1d
    Oct 3, 2020 at 18:29

1 Answer 1

0
$\begingroup$

You have an inaccuracy in the first equation regarding "H". Normally in the context of differentiating with respect to t, functions are assumed to be having a function of t as an argument, and if none is given, then it is normally assumed that H=H(t). In the case of your equation, H=H(z)=H(z(t)). See

What is the cosmological redshift drift effect? .

I suggest the other equations should also be in terms of z rather than t. You should also note that z(t0)=0, and z(t)=(1/a(t))-1.

I hope this helps.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.