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Antonio Bibiano edited section_Perturbations_The_linear_perturbations__.tex
almost 9 years ago
Commit id: 984aaa2b86d351d4a40a2b90de748e351b361488
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diff --git a/section_Perturbations_The_linear_perturbations__.tex b/section_Perturbations_The_linear_perturbations__.tex
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we can now use these relations to substitute the $\delta G$ terms in \ref{scalefactorfirst} after another differentiation to obtain a third order differential equation for the growth factor that will depend only on the cosmological quantities already introduced:
\begin{equation}
\label{scalefactorsecond}
D'''(a)+\frac{1}{2}\left( \begin{split}
&D'''(a)+\frac{1}{2}\left( 16-9\tilde{\Omega}(a) \right) \frac{D''(a)}{a} + \\
\frac{3}{2} &\frac{3}{2} \left( 8 - 11 \tilde{\Omega}_m(a) + 3 \tilde{\Omega}_m^2(a) - a \tilde{\Omega}_m'(a) \right) \frac{D'(a)}{a^2} = 0
\end{split}
\end{equation}
This equation lends itself to a numerical solution whose behavior is shown in [FIGURE] where the growth factor is shown as a function of redshift alongside with the $\Lambda CDM$ solution.
It is possible to see how the model predicts and enhancement of the growth for the $\nu < 0$ solution, this is due to the strengthening of the gravitational coupling at high redshift that allows to overcome the "repulsion" associated with the expansion of cause by the vacuum energy density.