# A model independent parametrization of the late time cosmic acceleration: constraints on the parameters from recent observations

## TL;DR

This paper introduces a model-independent, analytic parametrization of late-time cosmic acceleration using Pade approximation, constrains it with recent observations, and finds deviations from the standard b1CDM model, allowing phantom crossing and dynamical dark energy.

## Contribution

It presents a novel, fully analytic parametrization of the Hubble parameter valid for late-time and matter eras, with constraints from recent cosmological data.

## Key findings

- b1CDM model is 1 sigma away at low redshifts
- Phantom crossing is permitted by all datasets
- Dynamical dark energy models are favored at low redshifts

## Abstract

In this work, we have considered a model independent approach to study the nature of the late time cosmic acceleration. We have used the Pade approximation to parametrize the comoving distance. Consequently, from this comoving distance, we derive a parameterization for the Hubble parameter. Our parametrization is completely analytic and valid for late-time and matter dominated eras only. This parametrization possesses sub-percentage accuracy compared to any arbitrary cosmological model or parametrization up to matter dominated era. Using this parametrization, we put constraints on the parameters from recent low redshift cosmological observations including Planck 2018 distance priors. Our results show that the $\Lambda$CDM model is 1$\sigma$ to 2$\sigma$ away for lower redshifts. We find that the phantom crossing is allowed by all the combinations of dataset considered. We also find that the dynamical dark energy models are preferable at lower redshifts. Our study also shows that, at lower redshifts ($z<0.5$), phantom models are allowed at almost 1$\sigma$ confidence level.