Weinberg's Cosmology: Neglecting (1+z(eq)) in Denominator

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SUMMARY

The discussion centers on the equation from Steven Weinberg's book "Cosmology," specifically the term 〖H₁〗^2/〖H₀〗^2 =Ω₀(cri) (R₀⁴)/(R₁⁴(1+z(eq))). Participants question the neglect of the term “(1+z(eq))” in the denominator, suggesting that it is negligible when z is close to 0. This simplification is critical for understanding the dynamics of cosmic expansion as outlined by Weinberg.

PREREQUISITES
  • Understanding of cosmological equations and terms, particularly Hubble parameters (H₀ and H₁).
  • Familiarity with redshift concepts, specifically the significance of z(eq) in cosmology.
  • Knowledge of the Friedmann equations and their role in cosmological models.
  • Basic grasp of the implications of cosmic scale factors (R₀ and R₁).
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  • Study the Friedmann equations to understand their application in cosmology.
  • Research the implications of redshift in cosmological models, focusing on z(eq).
  • Examine Weinberg's "Cosmology" for detailed explanations of the terms used in the equation.
  • Explore the concept of critical density (Ω₀(cri)) and its relevance in cosmic expansion.
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EhsanZ
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In equation below
〖H₁〗^2/〖H₀〗^2 =Ω₀(cri) (R₀⁴)/(R₁⁴(1+z(eq)))

Why is the term “(1+z(eq))” negligible in denominator according to the term “ R₁⁴ ” ?

Weinburg did it in his book named "Cosmology".
 
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I would assume that z is incredibly close to 0.
 
EhsanZ said:
Weinburg did it in his book named "Cosmology".

I would like to see the context, but I don't feel like looking for this by flipping through Weinberg page-by-page. Could you please give the page number?
 

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