Confronting the Hubble Diagram of Gamma-Ray Bursts with Cardassian Cosmology

TL;DR

This study constructs a high-redshift Gamma-Ray Burst Hubble diagram to test the Cardassian cosmology model, finding it consistent with observations and comparable to the standard Lambda-CDM model, thus supporting its viability.

Contribution

First application of high-redshift GRBs to test the Cardassian cosmology, demonstrating its consistency with observational data and providing new insights into cosmic acceleration.

Findings

GRBs are consistent with Cardassian model predictions.

The universe's transition to acceleration occurs at redshift 0.2-0.7.

Results align with standard cosmological models.

Abstract

We construct the Hubble diagram (HD) of Gamma-Ray Bursts (GRBs) with redshifts reaching up to $z \sim 6$, by using five luminosity vs. luminosity indicator relations calibrated with the Cardassian cosmology. This model has a major interesting feature: despite of being matter-dominated and flat, it can explain the present accelerate expansion of the universe. This is the first study of this class of models using high redshift GRBs. We have performed a $\chi$-square statistical analysis of the GRBs calibrated with the Cardassian model, and also combined them with both the current Cosmic Microwave Background and Baryonic Acoustic Oscillation data. Our results show consistency between the current observational data and the model predictions. In particular, the best-fit parameters obtained from the $\chi^2$-analysis are in agreement with those obtained from the Concordance Cosmology ($\Lambda$-CDM). We determine the redshift at which the universe would start to follow the Cardassian expansion, i. e., \zc, and both the redshift at which the universe had started to accelerate, i. e., \zac, and the age-redshift relation $H_0t_0$. Our results also show that the universe, from the point of view of GRBs, had undergo a transition to acceleration at a redshift $z \approx 0.2-0.7$, which agrees with the SNIa results. Hence, after confronting the Cardassian scenario with the GRBs HD and proving its consistency with it, we conclude that GRBs should indeed be considered a complementary tool to several other astronomical observations for studies of high accuracy in cosmology.