I will discuss cosmological aspects of the QCD axion and more general axion-like particles. I will then show how axions can play a key role in well-motivated baryogenesis frameworks, strengthening their motivation beyond the strong CP problem. Next, I will introduce a simple axion–monopole model in which the axion dynamics induces an effective interaction between dark matter and dark energy. I will close with recent developments in cosmological signals of axion dark matter and prospects for future detection. 

Biography

Huangyu Xiao obtained his PhD from the University of Washington in 2022. Then he moved to Fermilab and U chicago for his first postdoc, and recently joined Boston University and Harvard University in 2025 for his second postdoc. His recent research interests include cosmological probes of axions and particle physics model building to explain the origin of baryon asymmetry.