The present work is based on a parametric reconstruction of the deceleration parameter q(z) in a model for the spatially flat FRW universe filled with dark energy and non-relativistic matter. In cosmology, the parametric reconstruction technique deals with an attempt to build up a model by choosing some specific evolution scenario for a cosmological parameter and then estimate the values of the parameters with the help of different observational datasets. In this paper, we have proposed a logarithmic parametrization of q(z) to probe the evolution history of the universe. Using the type Ia supernova, baryon acoustic oscillation and the cosmic microwave background datasets, the constraints on the arbitrary model parameters q 0 and q 1 are obtained (within 1σ and 2σ confidence limits) by χ 2 -minimization technique. We have then reconstructed the deceleration parameter, the total EoS parameter ω tot , the jerk parameter and have compared the reconstructed results of q(z) with other well-known parametrizations of q(z). We have also shown that two model selection criteria (namely, the Akaike information criterion and Bayesian information criterion) provide a clear indication that our reconstructed model is well consistent with other popular models.
In this paper it is shown that in Brans -Dicke theory, if one considers a non-minimal coupling between the matter and the scalar field, it can give rise to a late time accelerated expansion for the universe preceded by a decelerated expansion for very high values of the Brans -Dicke parameter ω.
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.
In this paper, we investigate the quintessence model with a minimally coupled scalar field in the context of recent supernovae observations. By choosing a particular form of the deceleration parameter q , which gives an early deceleration and late time acceleration for dust dominated model, we show that this sign flip in q can be obtained by a simple trigonometric potential. The early matter dominated model expands with q = 1/2 as desired and enters a negative q phase quite late during the evolution.
The present work shows that a combination of nonlinear contributions from the Ricci curvature in Einstein field equations can drive a late time acceleration of expansion of the universe. The transit from the decelerated to the accelerated phase of expansion takes place smoothly without having to resort to a study of asymptotic behaviour. This result emphasizes the need for thorough and critical examination of models with nonlinear contribution from the curvature.
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