Speaker
Description
Speaker: Kunfeng Lyu
Abstract: This talk will discuss how axion domain walls can play an role in early-Universe cosmology. First, I will show that a strongly supercooled MeV–GeV first-order phase transition can reshape QCD axion cosmology: reheating flattens the axion potential, induces mini kinetic misalignment, and could potentially generate QCD axion domain walls in the pre-inflationary case. Second, I will discuss electroweak baryogenesis from collapsing ALP domain walls, where wall motion across electroweak phases sources an effective baryon chemical potential and produces the observed baryon asymmetry without a strong first-order electroweak phase transition. These mechanisms provide new connections among axions, baryogenesis, phase transitions, and gravitational-wave signals.