Center of Gravity Seminar: Florian Niedermann

Title: The Hubble tension as a signature of a new phase transition

Abstract: The persistent discrepancy between early- and late-Universe measurements of the Hubble constant may point to new dark sector physics, built on the same fundamental principles that govern the visible sector. I will discuss a scenario in which this new physics takes the form of a symmetry breaking phase transition, dubbed Hot New Early Dark Energy. The latent heat released during the supercooled transition reheats the dark sector, altering the expansion history in a way that reconciles the discrepant measurements. The model introduces a dark gauge force that couples dark radiation to dark matter, leading to distinctive signatures that can be probed through the cosmic microwave background and the matter power spectrum.