Undergrad How is the value of tT^2 calculated for neucleosynthesis

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SUMMARY

The calculation of the value 0.74 for the nucleosynthesis era is derived from the temperature/time relation defined by the equation involving time (t in seconds), temperature (T in MeV), and the effective number of particle species (g*). In the standard model, g* is established as 10.75, which includes contributions from photons, electron-positron pairs, and neutrino flavors. The discussion highlights a lack of comprehensive resources beyond Wikipedia, prompting the user to seek further clarification and references on this specific calculation.

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  • Understanding of Big Bang nucleosynthesis
  • Familiarity with effective number of particle species (g*)
  • Basic knowledge of temperature and time relations in cosmology
  • Ability to interpret scientific equations and models
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Astrophysicists, cosmologists, and students studying Big Bang nucleosynthesis who seek a deeper understanding of the calculations and principles governing the early universe.

Buzz Bloom
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The following quote is from the Wikipedia article
https://en.wikipedia.org/wiki/Big_Bang_nucleosynthesis#Characteristics .
The temperature/time relation in this era can be given by the equation:​

tT2 EQ.png
where
t is time in seconds,
T is temperature in MeV, and
g* is the effective number of particle species.
(g* includes contributions of 2 from photons, 7/2 from electron-positron pairs and 7/4 from each neutrino flavor. In the standard model g* is 10.75).​
I would much appreciate seeing a reference citation or an explanation from someone about how the value 0.74 is calculated for the nucleosynthesis era.

By the way, when I searched the internet for this information, all I could find were articles that quoted the same material from Wikipedia.
 
Last edited:
Hi @Greg Bernhardt:

I think it is time to abandon this thread. I have the impression that there are no PF participants who are able to help me with respect to my question here.

I started a different thread to get help with respect to a different aspect of this thread.
I was pleased to get one useful response, and I am hoping to continue a discussion about that response.

Regards,
Buzz
 

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