Calculating dark energy and matter density

[Ranku]

What is the easiest way to calculate dark energy and matter density at any given age of the universe?

 

[Orodruin]

Given what input data?

 

[Ranku]

Given what input data?

Age of the universe.

 

[Orodruin]

Age of the universe.

That is clearly not sufficient.

 

[Ranku]

That is clearly not sufficient.

Hmm...I am trying to calculate how the density of dark energy and matter varies over the age of the universe.

 

[Orodruin]

So I ask again what input data you want to use.

 

[Ranku]

So I ask again what input data you want to use.

Then, in addition to age of the universe, either dark energy or matter density, or redshift.

 

[Orodruin]

You can easily compute how matter or dark energy density scales with the scale factor (and therefore with redshift). In order to know the actual density and how redshift relates to the age of the universe you must know the Hubble parameter today as well as the current ratio between the energy densities.

 

[Ranku]

You can easily compute how matter or dark energy density scales with the scale factor (and therefore with redshift). In order to know the actual density and how redshift relates to the age of the universe you must know the Hubble parameter today as well as the current ratio between the energy densities.

So using the Friedmann equation.

 

[Orodruin]

Yes, you need to integrate the Friedmann equations to connect the scale factor to the age of the universe.

 

[Ranku]

Yes, you need to integrate the Friedmann equations to connect the scale factor to the age of the universe.

Could you show how - not quite sure how to do it.

 

[Orodruin]

This should be described in any introductory level textbook on cosmology that discusses the Friedman equations.

 

[Ranku]

This should be described in any introductory level textbook on cosmology that discusses the Friedman equations.

Looked into a few, but couldn't find the "integration of the Friedman equations to connect with age of the universe".

 

[Lindsayforbes]

Hmm...I am trying to calculate how the density of dark energy and matter varies over the age of the universe.

I think it's a good question, Ranku. Why do you think Dark Energy varies over the age of the universe?

 

[Ranku]

I think it's a good question, Ranku. Why do you think Dark Energy varies over the age of the universe?

I was referring to how the comparative percentage of dark energy and matter changes over time - not in absolute terms, where only matter density decreases over time.

 

[stevebd1]

While you are talking about change in density, you still might find these two links of interest which look at the change in distribution of dark energy and matter over time-

http://www.einsteins-theory-of-relativity-4engineers.com/cosmocalc_2010.htm
adjust the redshift to see how the distribution of matter and dark energy has changed over the years

https://preposterousuniverse.com/wp-content/uploads/skytel-mar05.pdf
a great article by Sean Carroll that looks at dark energy and mentions the past and future distribution of dark energy

 

[Bandersnatch]

http://www.einsteins-theory-of-relativity-4engineers.com/cosmocalc_2010.htm
adjust the redshift to see how the distribution of matter and dark energy has changed over the years

Ugh, man. Use the newest version. You're missing out on cool features, including graphing.

 

[stevebd1]

Ugh, man. Use the newest version. You're missing out on cool features, including graphing.

Thanks for the input, while this is more up to date, unless I'm missing something, this doesn't show how the distribution of dark energy and matter has changed over the age of the universe which is what I wanted to point out.

 

[Bandersnatch]

But it does!