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

Abstract

In this paper, we have considered a spatially flat FRW universe filled with pressureless matter and dark energy. We have considered a phenomenological parametrization of the deceleration parameter q(z) and from this we have reconstructed the equation of state for dark energy ω φ (z). This divergence free parametrization of the deceleration parameter is inspired from one of the most popular parametrization of the dark energy equation of state given by Barboza and Alcaniz [30]. Using the combination of datasets (SN Ia + Hubble + 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 ω φ (z) and have found that the results are compatible with a ΛCDM universe if we consider SN Ia + Hubble data but inclusion of BAO/CMB data makes q(z) and ω φ (z) incompatible with ΛCDM model. The potential term for the present toy model is found to be functionally similar to a Higgs potential.

Phenomenological reconstruction of f(T) teleparallel gravity

“…Also, it can be shown that the deceleration parameter does not diverges as z → −1, so it is suitable to study the fate of the universe. Since the above parametric form is finite for all redshift values z ∈ [ − 1, ∞ ), it is valid to describe the entire cosmic history as mentioned in [23]. Using the parametric form (45) and (27), the Hubble-redshift relation can be written as…”

“…According to the values of the parameters q 0 and q 1 given in [23], the transition redshift z tr can be determined by setting w ef f (z tr ) = −1/3. This gives z tr ⋍ 0.75, 0.72, 0.8 and 0.54 according to the datasets H(z), SNIa, H(z)+SNIa and H(z)+SNIa+BAO/CMB, respectively.…”

“…1(c), we plot the evolution of the matter and the torsion density parameters according to the calculated values of the model parameters q 0 and q 1 as given in Ref. [23]. As shown by the plots, the matter density parameter crosses the unit boundary line at redshift 1 z 2 for the datasets H(z), SNIa and H(z)+SNIa, while for the combination H(z)+SNIa+BAO/CMB, the matter density parameter Ω m (z) crosses the unity at larger redshift z 10.…”

“…The main results of model 1 according to the values of (q0, q1) parameters as given in Ref. [23] and by using the matter density parameter constraint (51). In the later, we keep the strict measured values q0 as they are, while choosing the corresponding values of q1 to fulfill the constraint.…”

“…In Table I, we summarize the results of model 1 according to the values of the model parameters q 0 and q 1 as given in Ref. [23] and by applying the matter density constraint (51).…”