Orateur
Description
The measurement of the current expansion rate of the Universe, known as the Hubble constant (H0), has garnered significant interest lately, owing to the vastly different estimates obtained when probing different cosmological epochs. In particular, high-redshift measurements of the cosmic microwave background and the local low-redshift measurements using supernovae are statistically inconsistent with each other, giving rise to the unresolved discrepancy commonly known as the “Hubble Tension”. Gravitational waves emitted by merging compact binaries, detected routinely nowadays, offer a unique way to measure cosmological distances across different redshift epochs. If their redshifts can be determined independently, there is a prospect of measuring H0 directly with such sources by leveraging the distance-redshift relation. In this talk, I will discuss how redshifts are statistically inferred for events without an associated electromagnetic counterpart, the so-called dark sirens, which constitute the majority of detections by the LIGO-Virgo-KAGRA detector network. I will review the latest cosmological results from the GWTC-4.0 public gravitational wave transient catalog focusing on the methods employed, their limitations and future challenges for dark siren cosmology.
