Abstract We investigate in detail the influence of parametrizations of the dark energy equation of state on reconstructing dark energy geometrical parameters, such as the deceleration parameter q(z) and Om diagnostic. We use a type Ia supernova sample, baryon acoustic oscillation data, cosmic microwave background information along with twelve observational Hubble data points to constrain cosmological parameters. With the joint analysis of these current datasets, we find that the parametrizations of w(z) have little influence on the reconstruction result of q(z) and Om. The same is true for the transition (cosmic deceleration to acceleration) redshift zt , for which we find that for different parametrizations of w(z), the best fitted values of zt are very close to each other (about 0.65). All of our results are in good agreement with the ΛCDM model. Furthermore, using the combination of datasets, we do not find any signal of decreasing cosmic acceleration as suggested in some recent papers. The results suggest that the influence of the prior w(z) is not as severe as one may anticipate, and thus we can, to some extent, safely use a reasonable parametrization of w(z) to reconstruct some other dark energy parameters (e.g. q(z), Om) with a combination of datasets.

Keywords cosmology: observations — cosmology: cosmological parameters

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