Timeline for What is the current value for the temperature at which Recombination took place?
Current License: CC BY-SA 4.0
13 events
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| Dec 7, 2018 at 1:05 | vote | accept | CommunityBot | ||
| Nov 10, 2018 at 1:11 | comment | added | user32023 | @RobJeffries - Please double check my math. $h^2=\left(\frac{67.7}{100}\right) ^2=0.4529$. So, $\Omega_b=\frac{0.02205}{0.4529}=0.0487$. So baryonic matter makes up 4.87% of the universe's density according to $\Lambda CDM$. Is that right? | |
| Nov 7, 2018 at 13:17 | comment | added | user32023 | @RobJeffries - Thank you. That's useful information. I'm also interested in whether or not you agree with the (apparently) model independent calculations in the Curious Astronomer piece. I would rather be less precise if it meant being able to do the calculation without an assumption of Dark Matter and Dark Energy. | |
| Nov 7, 2018 at 6:57 | comment | added | ProfRob | @DonaldAirey The current density of baryons is not measured (accurately), it is calculated to be $3\times 10^4 \Omega_b h^2/8\pi G$ (with appropriate unit conversions). | |
| Nov 7, 2018 at 1:29 | comment | added | user32023 | The article referenced by N. Steinle doesn't use any $\lambda CDM$ concepts, not even $\Omega_b$. It determines the baryon density by looking at the current density and extrapolating backwards, just as you do with temperature: $(n_p+n_H)(z)=1.6(1+z)^3\space per\space m^3$. Would you agree with this method and does this make the Saha temperature estimate completely independent of Cosmological model? | |
| Nov 6, 2018 at 19:58 | history | edited | ProfRob | CC BY-SA 4.0 |
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| Nov 6, 2018 at 18:45 | comment | added | PM 2Ring | @DonaldAirey The simple model underlying the Saha equation means that Rob's results for various levels of recombination are only rough estimates. Wikipedia describes a more accurate 3-level atom model, and it also discusses modern refinements to that model which are expected to be accurate to 0.1%. The variations due to these different models of recombination have more impact than the variations due to cosmological model (those cosmological parameters impact the timing, though). | |
| Nov 6, 2018 at 18:18 | comment | added | ProfRob | @DonaldAirey Equation 10 in the cited source is almost the same as the one I quote (bar the sign error, which I have now corrected). It also uses $\Omega_b h^2$ because it relies (see equation 9) on the current baryon density of the universe. | |
| Nov 6, 2018 at 18:13 | history | edited | ProfRob | CC BY-SA 4.0 |
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| Nov 6, 2018 at 15:23 | comment | added | ProfRob | @DonaldAirey They depend on $\Omega_b h^2$ as shown. No other dependences that I can think of since the ionisation state of hydrogen at a given temperature has nothing to do with cosmological models other than through the baryon density which is given by the aforementioned parameter. What you calculate as "the" surface of last scattering depends on how it is defined. There is no "the" surface. | |
| Nov 6, 2018 at 13:45 | comment | added | user32023 | N. Steinle provide a link to a useful article on the subject. Equation 10 in the article (cited below) gives a model-independent calculation of the temperature. How dependent are these values that you quote on the cosmological model used? | |
| Nov 6, 2018 at 12:59 | comment | added | user32023 | That's a pretty wide range. Can you tell me which of these is generally used to calculate the distance to the Surface of Last Scattering? | |
| Nov 6, 2018 at 9:09 | history | answered | ProfRob | CC BY-SA 4.0 |