Timeline for Seeking a plot of the energy history of the Universe
Current License: CC BY-SA 4.0
12 events
| when toggle format | what | by | license | comment | |
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| Aug 11, 2022 at 13:09 | comment | added | Yukterez | @seVenVo1d - you can plot by t, the relation between t and a is simply t(a)=∫{0...a}[dã/ã/H(ã)] since da/dt=ȧ=H·a, so you have to do it numerically if you have a mixed component universe where radiation can't be neglected, but that's what computers are for (there are analytical solutions for that as well, but they are longer to type in than to perform the numerical integral) | |
| Aug 11, 2022 at 12:55 | comment | added | Yukterez | @G. Smith - The oregon plot is wrong while the alberta plot is correct, maybe they drew the first one by hand after setting to few sample points but the curves for radiation and matter must bend down on a logarithmic ρ(t) plot, see yukterez.net/f/einstein.equations/files/y#r2 - the mixture is no longer relevant in late times, where the discrepancy between the two plots occurs, so the first one is really wrong. | |
| Aug 11, 2022 at 12:27 | answer | added | Yukterez | timeline score: 0 | |
| Dec 15, 2020 at 20:18 | comment | added | seVenVo1d | It is not easy to plot $\rho$ vs $t$. You can make approximations to obtain $a(t)$ and then plot it but then it is not easy. You can plot $\rho$ vs $a$ | |
| Dec 13, 2020 at 22:23 | comment | added | G. Smith | It’s possible that they disagree because one of them takes into account how the radiation interacts with the matter, rather than considering a simple noninteracting mixture. I don’t understand how this interaction is usually modeled in cosmological computations. | |
| Dec 13, 2020 at 22:16 | comment | added | G. Smith | Note that both are log-log plots but in one the radiation and matter curves bend up and in the other they bend down. I haven’t tried the integration myself so I don’t know which is correct. Note that if the time dependence were $t^{-2}$ the two curves would be straight lines. | |
| Dec 13, 2020 at 22:14 | comment | added | G. Smith | sites.ualberta.ca/~pogosyan/teaching/ASTRO_122/lect30a/… | |
| Dec 13, 2020 at 22:13 | comment | added | G. Smith | pages.uoregon.edu/jimbrau/BrauImNew/Chap27/7th/… | |
| Dec 13, 2020 at 21:54 | comment | added | G. Smith | A complete history means that there are eras when the universe is not dominated by one of these, and the scale factor therefore does not evolve as you say. You can integrate the Friedmann equations taking into account all three contributions to get the curve you want, and the curve of each contribution, including their crossover points. I didn’t manage to find a graph of the total on the internet. I found two graphs of the three separate contributions but they were inconsistent with each other. | |
| Dec 13, 2020 at 19:49 | history | edited | Qmechanic♦ |
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| Dec 13, 2020 at 17:32 | history | edited | Solidification | CC BY-SA 4.0 |
added 45 characters in body
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| Dec 13, 2020 at 17:25 | history | asked | Solidification | CC BY-SA 4.0 |
