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I was wondering : going back in time up to the time when the universe is hot enough to create nucleons particle antiparticle pairs, when we are not much above this temperature threshold, the nucleons can not be considered ultrarelativistic and if they carry a fraction of the energy density not much smaller than the photons (correct?) and other lighter particles which by contrast are really ultrarelativistic then i would expect that globally the approximation of the ultrarelativistic fluid is not anymore valid (even though it is valid for a colder universe below the energy threshold for pair creation, that's strange!)... so the equation of state would not be rho=3p but somewhere in between rho=3p and p<<rho so that the densities would not decrease as 1/R⁴ but with a law momentarily somewhere in between 1/R³ and 1/R⁴ .. is that correct?, if not what did i miss? thank you in advance.

I found this strange that i read nowhere before that the equation of state could be significantly modified at such high temperatures ...

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# A Hadronic era equation of state

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