Measuring dark energy with DESI
Will Percival
Professor and Distinguished Research Chair in Astrophysics
University of Waterloo
Thursday, November 27, 2025
4:00 p.m.
In-person: PHY 145
Abstract: The Dark Energy Spectroscopic Instrument (DESI) is the first of a new generation of Dark Energy experiments, which probes evolution in the universe using galaxy clustering. Within the galaxy clustering signal, the projected location of the Baryon Acoustic Oscillations (BAO) acts as a standard ruler to map cosmic evolution. I will present the latest BAO results from the DESI Data Release 2 (DR2) sample, which contains 3 years of data, and their impact on our understanding of dark energy and neutrino masses. In particular, I will show how these data provide hints that the accelerated expansion of the universe might not match the predictions of Einstein’s cosmological constant. If there is time, I will explain some of the difficulties in expanding this work to model the full clustering signal, how this can be mitigated, and how the amplitude of the BAO signal can help us measure the Hubble constant.