My name is Jiaxi Yu (禹佳希). I graduated from EPFL in Switzerland in December 2024. I'm an observational cosmologist and my tool to explore the Universe and dark energy is galaxy redshift surveys. I've worked for the Sloan Digital Sky Survey (SDSS) and the Dark Energy Spectroscopic Instrument (DESI). I contributed to these surveys with studies on galaxy-halo connections (including quasars), galaxy mocks and spectroscopic systematics (redshift uncertainties and catastrophics). My research interest at IPMU is the cosmology of PFS and the early Universe.