Failure of Friedmann equation?

In summary, the paper discusses the failure of the Friedmann equation at late times due to the presence of subhorizon inhomogeneous gravitational fields. This can potentially explain the observed present acceleration of the Universe without the need for a Dark Energy component. The paper also mentions the assumption of homogeneity in the expansion of the Universe and how it may not be accurate at late times. This is supported by evidence such as the homogeneity of the CMB and the distribution of matter at large scales.
  • #1
wolram
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arXiv:astro-ph/0503715 v2 31 Mar 2005
Late time failure of Friedmann equation
Alessio Notari*
Physics Department, McGill University, 3600 University Road, Montr´eal, QC, H3A 2T8, Canada
(Dated: March 31, 2005)
It is widely believed that the assumption of homogeneity is a good zeroth order approximation for the expansion of our Universe. We analyze the correction due to subhorizon inhomogeneous gravitational fields. While at early times this contribution (which may act as a negative pressure
component) is perturbatively subdominant, we show that the perturbative series is likely to diverge at redshift of order 1, due to the growth of perturbations. In this case, the homogeneous Friedmann
equation can not be trusted at late times. We suggest that the puzzling observations of a present acceleration of the Universe, may just be due to the unjustified use of the Friedmann equation. This
would nicely solve the coincidence problem, without invoking a Dark Energy component.
 
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  • #2
Very interesting. I did not understand the mathematics and I am confused that this can work. I don't know how the current model describes the effect of non-linear corrections on the power spectrum. I can imagine that some perturbations may distort the background up to z ~ 2, but I cannot follow the steps in the paper. May be someone could explaint it.
 
  • #3
How do we know space is homogenous? Is the energy density the same everywhere?
 
  • #4
Starship said:
How do we know space is homogenous? Is the energy density the same everywhere?
As far as I know there are two indications for this: the homogeneity of the CMB and the distribution of matter at scales greater than 100 Mpc, which seams also to be homogeneous and isotropic.
 

1. What is the Friedmann equation?

The Friedmann equation is a mathematical equation that describes the evolution of the universe in terms of its expansion rate, energy density, and curvature. It is a key component of the cosmological models used to study the universe.

2. What does the failure of Friedmann equation mean?

The failure of Friedmann equation refers to situations where the equation does not accurately describe the evolution of the universe. This could occur due to unknown factors or incorrect assumptions made in the equation.

3. What are some possible reasons for the failure of Friedmann equation?

There are several possible reasons for the failure of Friedmann equation, including the presence of dark energy or dark matter, which are not accounted for in the equation. It could also be due to the limitations of the current cosmological models or incorrect assumptions about the nature of the universe.

4. How does the failure of Friedmann equation affect our understanding of the universe?

The failure of Friedmann equation can greatly impact our understanding of the universe. It could mean that our current cosmological models are incomplete or incorrect, and new theories and equations may be needed to fully explain the evolution of the universe. It also highlights the need for further research and exploration in order to gain a better understanding of the universe.

5. Are there any proposed solutions to the failure of Friedmann equation?

There are several proposed solutions to the failure of Friedmann equation, including modifying the equation to include new factors such as dark energy or dark matter. Other solutions involve revising the assumptions made in the equation or developing entirely new equations to describe the evolution of the universe. These proposed solutions are still being studied and debated in the scientific community.

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