Orateur
Description
I will talk about systematic differences between 2D and 3D Baryon Acoustic Oscillation (BAO) analyses. While 2D BAO measurements appear to ease the Hubble tension by accommodating both a higher H₀ and a larger sound horizon, they simultaneously introduce tension with Planck constraints on Ωₘh², reflecting systematic shifts relative to 3D analyses.
I then examine the apparent preference for dynamical dark energy in DESI DR2 when combined with Planck, and contrast it with SDSS BAO results. DESI probes a lowest mean redshift of z = 0.295, whereas SDSS reaches z = 0.11. Because w₀ and q₀ describe present-day cosmic expansion, access to lower-redshift data is decisive: SDSS constrains these parameters largely in a data-driven manner, while DESI’s higher minimum redshift makes them more dependent on model extrapolation. Adding low-redshift supernova data restores consistency with ΛCDM. I therefore argue that the apparent DESI preference for dynamical dark energy may reflect redshift sampling rather than new physics, and suggest that finer tomographic binning of the DESI Bright Galaxy Survey (BGS) to reach lower effective redshifts will be crucial to test this conclusion.