Dark energy history with 174 Gamma-ray bursts

We apply the Combo relation to a sample of 174 gamma-ray bursts to investigate possible evidence of evolving dark energy parameter w(z). We first build a gamma-ray burst Hubble's diagram and then we estimate the set ({Omega}m, {Omega}{Lambda}) in the framework of flat and non-flat {Lambda}CDM paradigm.

We then get bounds over the wCDM model, where w is thought to evolve with redshift, adopting two priors over the Hubble constant in tension at 4.4{sigma}, i.e., H0=(67.4{+/-}0.5)km/s/Mpc and H0=(74.03{+/-}1.42)km/s/Mpc. We show our new sample provides tighter constraints on {Omega}m since at z<~1.2 we see that w(z) agrees within 1{sigma} with the standard value w=-1. The situation is the opposite at larger z, where gamma-ray bursts better fix w(z) that seems to deviate from w=-1 at 2{sigma} and 4{sigma} level, depending on the redshift bins.