High-precision spectra for dynamical Dark Energy cosmologies from constant-w models

Abstract

Spanning the whole functional space of cosmologies with any admissibleDE state equations w(a) seems a need, in view of forthcomingobservations, namely those aiming to provide a tomography of cosmicshear. In this paper I show that this duty can be eased and that asuitable use of results for constant-w cosmologies can besufficient. More in detail, I ``assign'' here six cosmologies, aimingto span the space of state equations w(a) = wo+wa(1−a), forwo and wa values consistent with WMAP5 and WMAP7 releases andrun N-body simulations to work out their non-linear fluctuationspectra at various redshifts z. Such spectra are then compared withthose of suitable auxiliary models, characterized by constantw. For each z a different auxiliary model is needed. Spectraldiscrepancies between the assigned and the auxiliary models, up to k ≃ 2–3 h Mpc−1, are shown to keep within 1 %.Quite in general, discrepancies are smaller at greater z and exhibita specific trend across the wo and wa plane. Besides of aimingat simplifying the evaluation of spectra for a wide range of models,this paper also outlines a specific danger for future studies of theDE state equation, as models fairly distant on the w0-wa planecan be easily confused.