Illuminating the growth of cosmic structure with DESI

Abstract

In this talk, I will describe how DESI’s precise measurements of the large-scale galaxy distribution test our understanding of the standard cosmological model and probe the Universe’s initial conditions. First, I will show how DESI can measure the Hubble constant in several different ways, ultimately motivated to test new-physics resolutions to the Hubble tension. In particular, I will highlight a new method that, rather than building a distance ladder to test the distance-redshift relation, builds an energy density ladder to measure the Universe’s critical density, and thus directly measure the Hubble constant. DESI structure growth measurements play a critical role, as we compare the relative growth of baryonic and cold dark matter perturbations to link the baryon abundance (determined the early Universe) to the matter abundance measured by the geometry of the late Universe. Second, I will discuss ongoing work on tomographic structure growth constraints from the combination of DESI DR2 full-shape and CMB lensing cross-correlations with Planck and ACT. Adding CMB lensing cross-correlations considerably improves DESI DR2’s constraining power on dark energy, modified gravity, and neutrino mass. Finally, I will show how we can use DESI-CMB lensing cross-correlations as a particularly robust probe of local primordial non-Gaussianity, allowing us to differentiate single-field and multi-field inflation models.