Reconstructing cosmic evolution with a density parametrization

TL;DR

This paper introduces a density parametrization approach to model cosmic evolution, demonstrating a smooth transition from deceleration to acceleration, constrained by observational data, and predicting a future big crunch scenario.

Contribution

It presents a novel density parametrization scheme for dark energy models, constrained by multiple datasets, and compares its predictions with the standard $ ext{Lambda}$CDM model.

Findings

Shows a smooth transition from decelerating to accelerating universe

Predicts a future big crunch collapse

Provides best-fit cosmological parameters from observational data

Abstract

The current paper provides a comprehensive examination of a dark energy cosmological model in the classical regime, in which a generic scalar field is regarded as a dark energy source. Einstein's field equations are solved in model independent way i.e. using a scheme of cosmological parametrization. A parametrization of the density parameter as a function of the cosmic scale factor has been investigated in this line. The result is noteworthy because it shows a smooth transition from a decelerating to an accelerating phase in the recent past. The model parameters involved in the functional form of the parametrization approach utilized here were constrained using certain external datasets. The updated Hubble datasets containing 57 datapoints, 1048 points of recently compiled Pantheon datasets, and also the Baryon Acoustic Oscillation (BAO) datasets are used here to determine the best-fitting model parameter values. The expressions of several significant cosmological parameters are represented as a function of redshift `$z$' and illustrated visually for the best fit values of the model parameters to better comprehend cosmic evolution. The obtained model is also compared with the $\Lambda CDM$ model. Our model has a distinct behavior in future and shown a big crunch type collapse. The best fit values of the model parameters are also used to compute the current values of several physical and geometrical parameters, as well as phase transition redshift. To examine the nature of dark energy, certain cosmological tests and diagnostic analyses are done on the derived model.