First cosmology results from BAO in the Dark Energy Spectroscopic Instrument (DESI)

I will present a summary of the measurements of Baryon Acoustic Oscillations in the data release 1 (DR1) of the DESI survey and the interesting cosmological results derived from them. We use redshifts to over 6 million extragalactic objects - a factor of 3x used by SDSS! - to measure BAO and use this to determine the expansion rate of the Universe over the last 11 billion years, in seven redshift bins in the range from 0.1 to 4.2. Within a flat Lambda cold dark matter (LCDM) background model, DESI results are consistent with those from the CMB, and give a precision of 1% or better on the Hubble constant H_0. We derive an upper limit on the sum of the neutrino masses of M_nu below 0.072 eV (95% confidence): I will explain how this limit depends on priors and assumptions about the background expansion. But most interestingly, we find tentative evidence for a time varying dark energy, with the combination of DESI BAO, CMB and type Ia supernovae rejecting a cosmological constant with significances of between 2.5 and 3.9 sigma, depending on the dataset used.