Speaker
Description
Spectroscopic surveys map the three‑dimensional large‑scale structure of the Universe, providing precise tests of cosmic expansion and the growth of structure. The Dark Energy Spectroscopic Instrument (DESI) is a Stage‑IV experiment on the 4‑m Mayall telescope, using 5000 robotically positioned fibres to obtain spectra for more than 40 million galaxies and quasars over ~14,000 deg². I will briefly outline DESI’s design and survey strategy, including its target classes (BGS, LRGs, ELGs, QSOs, and the Lyα forest), and the analysis methods that underpin robust distance measurements.
I will then summarise DESI’s first cosmology results, highlighting per cent-level baryon acoustic oscillation (BAO) constraints that deliver the most precise expansion history to date across a broad redshift range. I will discuss internal consistency tests, comparisons with previous surveys, and the cosmological interpretation of these measurements within ΛCDM and simple extensions. In particular, I will examine the current hint (still at modest significance) for departures from a constant dark‑energy equation of state.
Finally, I will preview what the expanding DESI dataset will enable: tighter BAO and redshift‑space distortion measurements, improved full‑shape analyses, and sharpened constraints on curvature, gravity, and the sum of neutrino masses.