Terminology: Omega_0 = Omega_m? and more

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SUMMARY

The discussion centers on the interpretation of the term Omega_0 in cosmology, particularly in relation to Omega_m within the LambdaCDM model. It is established that Omega_0 is typically assumed to equal Omega_m, especially when Omega_m + Omega_Lambda = 1. The term "universal density" (rho_u) is also examined, with the consensus that it equates to Omega_m multiplied by the critical density (rho_critical). The confusion arises from the inconsistent notation used by authors in the referenced paper.

PREREQUISITES
  • Understanding of LambdaCDM cosmological model
  • Familiarity with cosmological density parameters (Omega_0, Omega_m, Omega_Lambda)
  • Knowledge of critical density in cosmology
  • Basic grasp of redshift concepts in astrophysics
NEXT STEPS
  • Research the LambdaCDM model and its implications on cosmological parameters
  • Study the relationship between Omega parameters and critical density
  • Explore the concept of redshift and its impact on universal density
  • Examine various cosmological papers for notation consistency and definitions
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Astronomers, cosmologists, and physics students seeking clarity on cosmological terminology and relationships between density parameters in the context of the LambdaCDM model.

hAndrew
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Some papers refer to Omega_0 without defining it. (Example: The first footnote on page 2 in http://arxiv.org/PS_cache/astro-ph/pdf/9908/9908159v3.pdf.) What's the normal assumption in this case? Omega_0 = Omega_m (Omega_m as in Omega_m + Omega_Lambda = 1 in LambdaCDM) fits the context, but seems strange in the above paper because the authors use the notation Omega_m elsewhere in the paper. Is Omega_0 = Omega_m?

A related question: That paper refers to the "universal density" rho_u. I haven't heard that term before. rho_u = Omega_m * rho_critical fits the context. Is "universal density" = Omega_m * rho_critical?
 
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Usually \Omega_0 refers to the fraction of the total density and the critical density today \Omega_0 = \rho_0 / \rho_{c,0}. The term "universtal density" in that paper seems to me to be equivalent to the density at a given redshift, but I might be wrong.
 

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