Speaker
Description
The Sandage–Loeb test provides a direct and model-independent probe of cosmic expansion by measuring the temporal drift of cosmological redshifts, offering a fundamentally different observable from standard distance-based probes. In this talk, I will present the current status of the ESPRESSO redshift drift experiment, focusing on recent results from the third observational epoch of a bright z ≃ 4 quasar, which extends the temporal baseline to ∼2 years and delivers the tightest constraints to date from this program. The measured drift remains consistent with ΛCDM expectations, with no evidence for a signal at the current sensitivity, and systematic effects are found to be subdominant at this stage.
Building on these results, I will discuss how redshift drift measurements evolve from a purely conceptual test into a realistic cosmological observable, and how their interpretation connects directly to the relation between H(z) and the time evolution of the scale factor. I will highlight the role of long-term monitoring in probing the expansion history in a differential and model-independent way, and the extent to which such measurements can test the consistency of the Friedmann–Lemaître framework.
Finally, I will outline the perspectives for a dedicated, multi-decade observational program combining ESPRESSO and future facilities such as ANDES, as well as potential synergies with low-redshift radio measurements. These efforts open the possibility of a first detection of the cosmological redshift drift within the coming decades, providing a new, direct window on the dynamics of the Universe.
| Parallel session | Astrophysical Probes of Dark Matter and Dark Energy |
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