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arXiv · 1805.10405

Versatile parametrization of the perturbation growth rate on the phantom brane

Alexander Viznyuk·Satadru Bag·Yuri Shtanov·Varun Sahni
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Abstract

We derive an analytical expression for the growth rate of matter density perturbations on the phantom brane (which is the normal branch of the Dvali-Gabadadze-Porrati model). This model is characterized by a phantomlike effective equation of state for dark energy at the present epoch. It agrees very well with observations. We demonstrate that the traditional parametrization $f=Ω_m^γ$ with a quasiconstant growth index $γ$ is not successful in this case. Based on a power series expansion at large redshifts, we propose a different parametrization for this model: $f=Ω_m^γ\left(1+\frac{b}{\ell H}\right)^β$, where $β$ and $b$ are constants. Our numerical simulations demonstrate that this new parametrization describes the growth rate with great accuracy - the maximum error being $\leq 0.1\%$ for parameter values consistent with observations.

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Alexander Viznyuk, Satadru Bag, Yuri Shtanov, Varun Sahni. 2018-09-17. Versatile parametrization of the perturbation growth rate on the phantom brane. https://doi.org/10.1103/physrevd.98.064024

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