Revisiting kink-like parametrization and constraints using OHD/Pantheon+/BAO samples

Abstract

We reexamine the kink-like parametrization of the deceleration parameter to derive constraints on the transition redshift from cosmic deceleration to acceleration. This is achieved using observational Hubble data, Type Ia Supernovae Pantheon+ samples and Baryon acoustic oscillations. In this parametrization, the value of the initial q parameter is qi, the final value is qf, the present value is denoted by q0, and the transition duration is given by α. We perform our calculations using the Monte Carlo Markov Chain method, utilizing the emcee package. Under the assumption of a flat geometry, we constrain the range of possible values for three scenarios: when qf is unrestricted, when qf is equal to −1, and when α is 1/3. This is done assuming that qi=1/2. Here, we achieve that the SN data fixes the free parameters tightly as in the flat ΛCDM for unrestricted qf. In addition, if we fix qf=−1, the model behaves well as the ΛCDM for the combined dataset. We also acquire the current value of the deceleration parameter, which is consistent with the latest results that assume the ΛCDM model. Furthermore, we observe a deviation from the standard ΛCDM model in the current model based on the evolution of j(z), and it is evident that the universe transitions from deceleration to acceleration and will eventually reach the ΛCDM model in the near future.