PPC 2025: XVIII International Conference on Interconnections between Particle Physics and Cosmology

Data-Driven Solutions to the Hubble Tension: Modifications of Cosmological Recombination and the Primordial Power Spectrum

Not scheduled

30m

Roosevelt Room I (SpringHill Suites Conference Center Deadwood)

Speaker

Nanoom Lee (Johns Hopkins University)

Description

We present a data-driven approach to constructing modifications of the fiducial $\mathrm{\Lambda }$CDM model as possible solutions to the Hubble tension, using the Fisher bias formalism. We apply this method to two scenarios: modifications to the cosmological recombination and modifications to the primordial scalar power spectrum. In both cases, analyzing Planck CMB temperature and polarization anisotropy data, we identify solutions that yield an inferred Hubble constant fully consistent with SH0ES measurements. However, these solutions typically predict a low total matter density, ${\mathrm{\Omega }}_m$, leading to tensions with baryon acoustic oscillation (BAO) and uncalibrated supernova (SNIa) data. In the case of modifying the primordial power spectrum, we also find that the solutions are inconsistent with the Planck CMB lensing potential. These results indicate that resolving the Hubble tension through modifications to early Universe physics, while maintaining consistency with various cosmological observables, remains a significant challenge. Our framework provides a powerful tool for systematically exploring the existence of potential solutions.