Physics, asked by suni1177, 1 year ago

What are “the background equations” in cosmology?

Answers

Answered by 27June2018
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I think he's on about the equations that govern the general evidence we have for how the cosmos is. Such as the 3K CMB radiation, red shift and some others.

3K background

For the CMB, we the image that you have probably seen. This is Planck's radiation law, that says the temperature is proportion the the square of the angular frequency of the radiation.

TT ~ ν2ν2 A more in depth view is found here

Red Shift This notion is understood the Doppler effect, which is essentially the addition of velocity vectors and it's effect on the frequency. There is a relativistic treatment but the standard is:

f=c+vrc+vsf0


hope it helps you
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¶potter¶
Answered by Anonymous
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Explanation:

No idea in this context so I can't provide an answer for sure, but it could just be talking about the mean equations -- when you introduce the perturbations, if you collect all the mean terms together you get a set of equations for those and when you collect all the perturbed terms together, you get the perturbation equation. And I think that is what the question is implying -- when you do the perturbation and set ϵ=0, you get something called the background equations in terms of a0 and ρ0. – tpg2114♦ Feb 23 '16 at 11:37

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