Is the Friedmann Equation Failing at Late Times?

[wolram]

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.

 

[hellfire]

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.

 

[Starship]

How do we know space is homogenous? Is the energy density the same everywhere?

 

[hellfire]

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.