Integrating Friedmann Equation of Multi-component universe respect to a and t

AI Thread Summary
The discussion focuses on integrating the Friedmann equation to find the relationship between scale factor 'a' and time 't' in a multi-component universe. The user seeks assistance specifically for two scenarios: a matter-curvature only universe and a matter-lambda only universe. The provided integrals for each scenario are outlined, with suggestions to substitute x = 1/a and utilize a table of integrals for simplification. The resulting expression for the matter-lambda case is given, highlighting the dependency on the density parameters. Overall, the thread emphasizes the complexity of deriving these relationships in cosmological models.
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I am having a trouble finding relationship between 'a' and 't' by integrating friedmann equation in a multi-component universe.

It would be very helpful if you can help me with just
matter-curvature only universe and matter-lambda only universe.

The two integrals looks like following.

Matter-curvature only:

H_0 t = ∫_0^a \frac{da}{[Ω_0/a + (1-Ω_0)]^{1/2}}

Matter-Lambda only:

H_0 t = ∫_0^a \frac{da}{[Ω_0/a + (1-Ω_0)a^2]^{1/2}}

Thank you for your help.
 
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Try substituting x = 1/a and then use a table of integrals.
 
with matter lambda the result is
a(t)=(ro_matter/ro_lambda)^(1/3)*[sinh[(6*Pi*ro_lambda*G)^(1/2)*t]^(2/3)
Where ro_x/ro_critical=omega_0x
 
https://en.wikipedia.org/wiki/Recombination_(cosmology) Was a matter density right after the decoupling low enough to consider the vacuum as the actual vacuum, and not the medium through which the light propagates with the speed lower than ##({\epsilon_0\mu_0})^{-1/2}##? I'm asking this in context of the calculation of the observable universe radius, where the time integral of the inverse of the scale factor is multiplied by the constant speed of light ##c##.
Why was the Hubble constant assumed to be decreasing and slowing down (decelerating) the expansion rate of the Universe, while at the same time Dark Energy is presumably accelerating the expansion? And to thicken the plot. recent news from NASA indicates that the Hubble constant is now increasing. Can you clarify this enigma? Also., if the Hubble constant eventually decreases, why is there a lower limit to its value?

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