Abstract

The cosmography method is a model-independent technique used to reconstruct the Hubble expansion of the Universe at low redshifts. In this method, using the Hubble diagrams from Type Ia Supernovae (SNIa) in Pantheon catalog, quasars and Gamma-Ray Bursts (GRB), we put observational constraints on the cosmographic parameters in holographic dark energy (HDE) and concordance varLambda CDM models by minimizing the error function chi ^2 based on the statistical Markov Chain Monte Carlo (MCMC) algorithm. Then, we compare the results of the models with the results of the model-independent cosmography method. Except for the Pantheon sample, we observe that there is a big tension between standard cosmology and Hubble diagram observations, while the HDE model remains consistent in all cases. Then we use different combinations of Hubble diagram data to reconstruct the Hubble parameter of the model and compare it with the observed Hubble data. We observe that the Hubble parameter reconstructed from the model-independent cosmography method has the smallest deviation from the Hubble data and the varLambda CDM (HDE) model has the largest (middle) deviation, especially when we keep the observational data point 226^{+8.0}_{-0.8} at redshift z=2.36 in the analysis. On the contrary, in the redshift z <1, we see that the compatibility of varLambda CDM cosmology and observation is even better than the model independent cosmography method.

Highlights

  • Itational lensing [16,17,18]

  • Measuring the discrepancy between the cosmographic parameters obtained in the dark energy (DE) model and the parameters obtained from the model-independent cosmography method can be regarded as the tension between the DE model and observations

  • We have shown that both the holographic dark energy (HDE) and the ΛCDM models are consistent with the Hubble diagram of SNIa observations

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Summary

Introduction

In order to solve these problems, different DE models with time-varying EoS parameters have been proposed in the literature. The best fit values of the cosmological parameters can be determined by parameterizing the cosmological quantities [36] Another model-independent method to study the history of the expansion of the Universe that we used in this work is the cosmography method We use different combinations of Hubble diagrams from SNIa, quasars, and GRB to study the HDE model in the context of cosmography method, and compare the results with the results of standard ΛCDM cosmology. By comparing the constrained values of the cosmographic parameters of the HDE and ΛCDM models with the values obtained from the model-independent cosmography method, we can check these models and their consistency with the Hubble diagram observations.

The HDE model
The cosmography approach
Observational constraints on cosmographic parameters
Quasar
Hubble parameter reconstruction
Findings
Conclusions
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