Title: A New Lens on the Universe’s Expansion and the Growth of Matter Perturbations
Speaker: Alex Krowlewski (U of Waterloo)
Abstract:
Measurements of the growth of cosmic structure and the Universe’s expansion rate have recently attracted much attention due to tensions with the standard cosmological model. Are these statistical flukes or hints of new physics? Luckily, new cosmological datasets are an embarrassment of riches--in particular, the combination of maps of the cosmic microwave background (CMB) and DESI’s 3D map of 50 million galaxies. First, I'll show how we measure structure growth (from initial seeds to galaxy clusters) with the subtle distortions imprinted on the CMB as it is gravitationally lensed by foreground galaxies. I used this technique to achieve cutting-edge precision (<2% errors) on structure growth, and found no evidence for tension with the standard model. Second, I developed a new method to measure the Hubble constant by directly inferring the Universe’s total energy density, calibrated using the baryon oscillation amplitude in galaxy clustering. I will show the first application of this method to BOSS and DESI-DR1 data, and its potential to resolve the Hubble tension with future DESI and Euclid data. Finally, I will discuss some other avenues for discovery with DESI: detection (or not?) of cosmological parity violation; finding the sources of the unresolved gamma-ray background (near and low-mass or distant and high-mass); and lastly, the status of the search for dark energy.
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