Non-linear structure formation for dark energy models with a Steep Equation of State

Abstract

We study the non-linear regime of large scale structure formation considering a dynamical dark energy (DE) component determined by a Steep Equation of State parametrization (SEoS), w(z)=w0+wi(z/zT)q1+(z/zT)q. In order to perform the model exploration at low computational cost, we modified the publicly available L-PICOLA code. We incorporate the DE model employing the first and second-order matter perturbations in the Lagrangian frame and the expansion parameter. We analyse deviations of dynamical DE models w.r.t. ΛCDM in the non-linear matter power spectrum, Pk, the halo mass function (HMF), and the two-point correlation function (2PCF) . We investigate the effect of a steep (SEoS-I) and smooth transition (CPL-lim) in the DE equation of state (EoS) . In the former case, we found an overall impact in the Pk at the level of ∼ 2–3% while, for the latter, we found ∼ 3–4% differences w.r.t. ΛCDM at 0z=. The HMF shows the possibility to distinguish between the models at the high mass end. For the best-fit model, dubbed SEoS-II, we observe large deviations from ΛCDM . This is explained by the combined effect of the dynamical DE with the different amount of matter, Ωm0, and the higher value for H0. Regarding the 2PCF, our results are relatively robust with deviations w.r.t. ΛCDM or the order ∼ 1–2 % for SEoS-I and CPL-lim, and more significant deviation for SEoS-II throughout the r range, making SEoS-I a competitive model. Finally, we conclude that the search for viable DE models (like the SEoS) must include non-linear growth constraints.