Iván Durán, Fernando Atrio-Barandela, Diego Pavón
According to the Harrison-Zel'dovich prescription, the amplitude of matter
density perturbations at horizon crossing is the same at all scales. Based on
this prescription, we show how to construct the matter power spectrum of
generic Dark Energy (DE) models from the power spectrum of a $\Lambda$CDM model
without the need of solving in full the dynamical equations describing the
evolution of all energy density perturbations. Our approach allows to make
model predictions of observables that can be expressed in terms of the matter
power spectrum alone, such as the amplitude of matter fluctuations, peculiar
velocities, Cosmic Microwave Background temperature anisotropies on large
angular scales or the weak lensing convergence spectrum. Then, models that have
been tested only at the background level using the rate of the expansion of the
Universe can now be tested using data on gravitational clustering and on large
scale structure. This method can save a lot of effort in checking the validity
of DE models. As an example of the accurateness of the approximation used, we
compute the power spectrum of a DE model with $w_{DE}=-0.5$ (ruled out by
observations, but easy to compare to numerical solutions) using our methodology
and discuss the constraints imposed by the low multipoles of the Cosmic
Microwave Background.
View original:
http://arxiv.org/abs/1109.4038
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