Speaker
Description
The discrepancy in the Hubble constant (H0) measurements between the local and early Universe, commonly referred to as the "Hubble tension", has now reached a statistical significance of 4-7σ. This suggests potential physics beyond the flat ΛCDM model. In this talk, I present compelling observational evidence for evolving dark energy derived from a new sample of Active Galactic Nuclei (AGN) cross-matched from SDSS and XMM-Newton. By analysing the Hubble diagram of ~1,900 AGN up to redshift z~3.5, we find significant deviations from the standard cosmological model. To validate these results, I compare our findings with a separate AGN-based Hubble diagram across a similar redshift range, which utilises the relationship between variability amplitude, characteristic timescales, and intrinsic luminosity.
This is the first time that two entirely independent methodologies using AGN as standard(isable) candles have yielded consistent results. These findings provide robust support for an evolving dark energy component and a necessary revision of the standard cosmological framework.