Topic 1: Resolving Debate Over the Tip of the Red Giant Branch Method's Calibration and its Application to Measuring the Hubble Constant Topic 2: The CAMELS-SAM simulations: new 'hump' for constraining cosmology with galaxy clustering and neural networks

Abstract 1: Measurements of the Hubble constant (H0) as determined via the Cepheid-supernovae distance ladder appear to provide strong evidence for physics beyond LCDM. However, in the Carnegie Chicago Hubble Program (CCHP), we used the Tip of the Red Giant Branch (TRGB) method to determine a value of H0 that is less in tension with LCDM than the Cepheid-SN value, weakening the claim for new physics. This disagreement between the TRGB and Cepheids has sparked debate over the CCHP's calibration of the TRGB zero point, the value of which is perfectly degenerate with H0. In this talk, I will present my recent findings that settle the issue through careful experimental design and state-of-the-art measurements. I will demonstrate that this contention over TRGB calibration was sourced by systematic biases (due to, e.g., metallicity, age, and dust) in literature measurements. The final result is a self-consistent TRGB calibration determined to its highest accuracy yet. The new result also confirms the existence of the Cepheid-TRGB distance discrepancy and that the likeliest explanation for it is systematic error in measurements of the most distant SN host galaxies (20-30 Mpc). The TRGB has an exciting future ahead. With data from my forthcoming Hubble Space Telescope program, the definitive Hubble Telescope calibration of the TRGB will be determined. The door will also be opened for the method to be used in the near-infrared, which promises a tenfold increase in the number of TRGB-calibrated SNe Ia—a prospect that would change the face of distance ladder H0 experiments.