Redshift in Terms of k | General Relativity

In summary, the conversation discusses studying general relativity, specifically the FRW universe, using Hobson's. It mentions the equations for a matter universe with curvature and the expression for Ωm + Ωk. The topic of redshift is also brought up, with a question about how to find it in terms of Ωk when curvature dominates. The conversation concludes with the solution to this question.
  • #1
unscientific
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Hi, I have been studying general relativity using Hobson's lately, particularly about the FRW universe.

I know that for a matter universe with curvature,
[tex]H^2 = \left( \frac{\dot a}{a} \right)^2 = \frac{8\pi G}{3} \rho_m -\frac{kc^2}{a^2} [/tex]
Another expression I came across is also
[tex]1 = \Omega_m + \Omega_k[/tex]

I am thinking when the curvature dominates at late times what would the redshift be like.
When curvature dominates, the FRW equation is simply ##\left( \frac{\dot a}{a} \right)^2 = \frac{8\pi G}{3} \rho_m -\frac{kc^2}{a^2} ##.

I know that redshift is ##1+z = \frac{1}{a}##. How do I find redshift in terms of ##\Omega_k##?
 
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  • #2
solved.
 

1. What is redshift in terms of k?

Redshift in terms of k refers to the amount by which light from distant objects is shifted towards longer wavelengths due to the expansion of the universe. This is described by the cosmological redshift formula, which includes the cosmological constant (k) as a parameter.

2. How is redshift related to general relativity?

Redshift is related to general relativity through the theory of gravitation. According to general relativity, the observed redshift of light from distant galaxies is a result of the expansion of the universe and the stretching of space-time.

3. Can redshift be used to measure the expansion rate of the universe?

Yes, redshift can be used to measure the expansion rate of the universe. The amount of redshift observed in light from distant objects can be used to calculate the distance to those objects and their relative velocity. This information can then be used to determine the expansion rate of the universe.

4. What is the difference between redshift and blueshift?

Redshift and blueshift are the opposite effects of the Doppler effect on the wavelength of light. Redshift occurs when an object is moving away from an observer, causing the light to be stretched to longer wavelengths. Blueshift occurs when an object is moving towards an observer, causing the light to be compressed to shorter wavelengths.

5. How does redshift support the Big Bang theory?

Redshift is a key piece of evidence that supports the Big Bang theory. The observation of redshift in light from distant galaxies suggests that the universe is expanding, which is a fundamental aspect of the Big Bang theory. Additionally, the amount of redshift observed in the cosmic microwave background radiation provides further evidence for the Big Bang model.

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