Imprint of a Steep Equation of State in the growth of structure

Mariana Jaber; Erick Almaraz; Axel de la Macorra

doi:10.1016/j.astropartphys.2019.102388

paper

Imprint of a Steep Equation of State in the growth of structure

arXiv:1906.09522 · doi:10.1016/j.astropartphys.2019.102388

Abstract

We study the cosmological properties of a dynamical of dark energy (DE) component determined by a Steep Equation of State (SEoS) $w (z) = w_{0} + w_{i} \frac{( z / z _{T} ) ^{q}}{1 + ( z / z _{T} ) ^{q}}$ . The SEoS has a transition at $z_{T}$ between two pivotal values ( $w_{i}, w_{0}$ ) which can be taken as an early time and present day values of $w$ and the steepness is given by $q$ . We describe the impact of this dynamical DE at background and perturbative level. The steepness of the transition has a better cosmological fit than a conventional CPL model with $w = w_{0} + w_{a} (1 - a)$ . Furthermore, we analyze the impact of steepness of the transition in the growth of matter perturbations and structure formation. This is manifest in the linear matter power spectrum, $P (k)$ , the logarithmic growth function, $f σ_{8} (z)$ , and the differential mass function $d n / d lo g M (z = 0)$ . The differences in these last three quantities is at a percent-level using the same cosmological baseline parameters in our SEoS and a $Λ C D M$ model. However, we find an increase in the power spectrum, producing a bump at $k \approx k_{T}$ with $k_{T} \equiv a_{T} H (a_{T})$ the mode associated to the time of the steep transition ( $a_{T} = 1/ (1 + z_{T})$ ). Different dynamics of DE lead to a different amount of DM at present time which has an impact in Power Spectrum and accordingly in structure formation.

10 pages, 7 figures