A divergence-free parametrization of deceleration parameter for scalar field dark energy

In this paper, we have considered a spatially flat FRW universe filled with pressureless matter and dark energy (DE). We have considered a phenomenological parametrization of the deceleration parameter q(z) and from this, we have reconstructed the equation-of-state (EoS) for DE omega(phi)(z). This divergence-free parametrization of the deceleration parameter is inspired from one of the most popular parametrization of the DE EoS given by Barboza and Alcaniz [see E. M. Barboza and J. S. Alcaniz, Phys. Lett. B 666 (2008) 415]. Using the combination of datasets (Type Ia Supernova (SN Ia) + Hubble + baryonic acoustic oscillations/cosmic microwave background (BAO/CMB)), we have constrained the transition redshift z(t) (at which the universe switches from a decelerating to an accelerating phase) and have found the best fit value of z(t). We have also compared the reconstructed results of q(z) and omega(phi)(z) and have found that the results are compatible with a Lambda CDM universe if we consider SN Ia + Hubble data, but inclusion of BAO/CMB data makes q(z) and omega(phi)(z) incompatible with Lambda CDM model. The potential term for the present toy model is found to be functionally similar to a Higgs potential.