EMPRESS. VIII. A New Determination of Primordial He Abundance with Extremely Metal-Poor Galaxies: A Suggestion of the Lepton Asymmetry and Implications for the Hubble Tension

Akinori Matsumoto, Masami Ouchi, Kimihiko Nakajima +42

The primordial He abundance $Y_{\mathrm{P}}$ is a powerful probe of cosmology. Currently, $Y_{\mathrm{P}}$ is best determined by observations of metal-poor galaxies, while there are on…