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

TL;DR

This study reexamines a kink-like parametrization of the deceleration parameter using diverse cosmological data to constrain the universe's transition from deceleration to acceleration, revealing consistency with the Lambda-CDM model and potential deviations.

Contribution

It introduces a detailed analysis of the kink-like parametrization with observational data, providing new constraints and insights into the cosmic transition redshift and model behavior.

Findings

Constraints on transition redshift from observational data

Current deceleration parameter aligns with Lambda-CDM

Evidence of deviation in j(z) evolution from standard model

Abstract

We reexamine the kink-like parameterization 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 $q_{i}$, the final value is $q_f$, the present value is denoted by $q_{0}$, and the transition duration is given by $\alpha$. 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 $q_{f}$ is unrestricted, when $q_{f}$ is equal to $-1$, and when $\alpha$ is $1/3$. This is done assuming that $q_{i}=1/2$. Here, we achieve that the $SN$ data fixes the free parameters tightly as in the flat $\Lambda$CDM for unrestricted $q_{f}$. In addition, if we fix $q_{f}=-1$, the model behaves well as the $\Lambda$CDM for the combined dataset. We also acquire the current value of the deceleration parameter, which is consistent with the latest results that assume the $\Lambda$CDM model. Furthermore, we observe a deviation from the standard $\Lambda$CDM 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 $\Lambda$CDM model in the near future.