Abstract
In this paper, we propose a new phenomenological two parameter parameterization of q(z) to constrain barotropic dark energy models by considering a spatially flat Universe, neglecting the radiation component, and reconstructing the effective equation of state (EoS). This two free-parameter EoS reconstruction shows a non-monotonic behavior, pointing to a more general fitting for the scalar field models, like thawing and freezing models. We constrain the q(z) free parameters using the observational data of the Hubble parameter obtained from cosmic chronometers, the joint-light-analysis Type Ia Supernovae (SNIa) sample, the Pantheon (SNIa) sample, and a joint analysis from these data. We obtain, for the joint analysis with the Pantheon (SNIa) sample a value of q(z) today, q_0=-0.51begin{array}{c} +0.09 -0.10 end{array}, and a transition redshift, z_t=0.65begin{array}{c} +0.19 -0.17 end{array} (when the Universe change from an decelerated phase to an accelerated one). The effective EoS reconstruction and the omega '–omega plane analysis point towards a transition over the phantom divide, i.e. omega =-1, which is consistent with a non parametric EoS reconstruction reported by other authors.
Highlights
The standard way to examine these models is to calculate the Friedmann and Raychaudhuri equations in a background cosmology to constrain their free parameters
There are two techniques to measure the cosmic expansion at different redshifts: using the baryon acoustic oscillation analysis or applying the differential age technique (DA) in cosmic chronometers, i.e. passive-early-type galaxies
The matter component is dominant with respect to the dark energy component for high redshift values, the opposite occurs at late times
Summary
The standard way to examine these models is to calculate the Friedmann and Raychaudhuri equations in a background cosmology to constrain their free parameters (see for example [17]). A model-independent approach is to investigate the cosmographic parameters that characterize the kinematics of the cosmic expansion [18,19,20,21,22,23] The advantage of this procedure is that the only assumption is the Cosmological Principle, i.e. an homogeneous and isotropic Universe, without speculating about its composition. By probing the cosmographic parameters using cosmological data, we can associate them to a given dynamical DE entity and reconstruct its features as well as the Universe dynamics In this vein, several authors have proposed a number of functions to parameterize the deceleration parameter q(z) (see for example [25,26,27,28,29,30] for recent studies) and associate its features to a some DE model.
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