Cosmographic parameters in model-independent approaches

TL;DR

This study evaluates the effectiveness of the cosmographic approach in a model-independent manner for understanding the universe's evolution, comparing it with Gaussian process and Genetic algorithm methods using SNIa and Hubble data.

Contribution

It provides a comparative analysis of cosmography, Gaussian process, and Genetic algorithm approaches, highlighting the limitations and biases of cosmography at higher redshifts.

Findings

Cosmography results are less accurate compared to other methods.

Tensions exceeding 3σ are observed between cosmography and ΛCDM.

Cosmography shows biases and limitations at higher redshifts.

Abstract

Cosmographic approach, a Taylor expansion of the Hubble function, has been used as a model-independent method to investigate the evolution of the universe in the presence of cosmological data. Apart from possible technical problems like the radius of convergence, there is an ongoing debates about the tensions appear when one investigates some high redshift cosmological data. In this work, we consider two common data sets namely SNIa (Pantheon sample) and the Hubble data to investigate advantages and disadvantages of the cosmographic approach. To do this, we obtain the evolution of cosmographic functions using cosmographic method as well as two other well known model-independent approaches namely, the Gaussian process and the Genetic algorithm. We also assume $\Lambda$CDM model as concordance model to compare the results of mentioned approaches. Our results indicate that the results of cosmography comparing with the other approaches, are not exact enough. Considering the Hubble data which is less certain, the results of $q_0$ and $j_0$ obtained in cosmography, provides a tension at more than $3\sigma$ away from the best result of $\Lambda$CDM. Assuming both of data samples in different approaches we show that the cosmographic approach, because of providing some biased results, is not the best approach for reconstruction of cosmographic functions, especially at higher redshifts.